Data transmission method, device, and system

Abstract

The present application provides a data transmission method, apparatus and system. The method includes: a source network device performs a cascading process on at least two data units to obtain a first data packet, and sends the first data packet to a target network device through a first tunnel, where data included in the at least two data units belong to the same radio bearer or quality of service flow of a terminal device, and the first data packet is a Packet Data Convergence Protocol PDCP layer data packet or a Service Data Adaptation Protocol SDAP layer data packet. According to the above method, multiple data units are cascaded to obtain one data unit, so that the header overhead of the cascading data packets can be reduced, a lossless handover under the cascading function can be implemented, and a cascading gain can be obtained.

Description

[Technical field]

[0001] The present application relates to the field of communication technologies, and in particular to data transmission methods, devices and systems. [Background technology]

[0002] In a new radio (NR) system, the protocol stack between a base station and a terminal device includes the following protocol layers: a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a media access control (MAC) layer, and a physical (PHY) layer.

[0003] Before a data packet is transmitted, the data packet needs to be processed in the SDAP layer, PDCP layer, RLC layer, MAC layer, and physical layer in order. Finally, the data packet is transmitted. Correspondingly, the receiving side performs the reverse processing in the reverse protocol layer order. When the data packet is processed in each protocol layer, a data packet header needs to be added. For example, when a terminal device is handed over from a source base station to a target base station, the source base station needs to forward the data of the terminal device to the target base station. When the source base station processes the data packet in the SDAP layer, an SDAP layer packet header is added. Similarly, when the data packet is processed in the PDCP layer, a PDCP layer packet header is added. The size of the packet header is about 6 bytes. Therefore, when the data packet is transmitted from the source base station to the target base station, the packet header overhead is finally increased by about a dozen bytes. The overhead is relatively high. Moreover, in the process of adding a packet header to the data packet, a large amount of hardware resources needs to be consumed, which reduces the data processing efficiency.

[0004] Therefore, how to improve data transmission efficiency and reduce data overhead is an urgent problem to be solved. Summary of the Invention

[0005] The present application provides a data transmission method, apparatus and system to improve data transmission efficiency and reduce data overhead.

[0006] According to a first aspect, the present application provides a data transmission method. The method is applied to a scenario in which a source network device transfers data of a terminal device to a target network device in a terminal device handover process. An execution subject of the method is the source network device or a module in the source network device. An example in which the source network device is the execution subject is used here for explanation. The method includes the source network device performing a cascade connection process on at least two data units to obtain a first data packet. The source network device may transmit the first data packet to the target network device through a first tunnel. The data included in the at least two data units belong to the same radio bearer or quality of service flow of the terminal device, and the first data packet is a Packet Data Convergence Protocol PDCP layer data packet or a Service Data Adaptation Protocol SDAP layer data packet.

[0007] According to the above method, multiple data units are cascaded to obtain one data packet, so that the header overhead of the cascading data packet can be reduced, and lossless handover under the cascading function can be implemented, thereby obtaining cascading gain.

[0008] In a possible implementation, the source network device may further send first information to the target network device via the first tunnel, where the first information indicates that the first data packet is a cascading data packet.

[0009] In a possible implementation, the source network device may further send a second data packet and second information to the target network device via the first tunnel, the second information indicating that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0010] In the above implementation, the cascading data packets and the non-cascading data packets of the same radio bearer or quality of service flow are forwarded through a public tunnel (e.g., the first tunnel), and the type of the data packet (cascading data packet or non-cascading data packet) is further indicated. In this way, the header overhead of the cascading data packets can be reduced, and lossless handover under the cascading connection function can be implemented.

[0011] In a possible implementation, the source network device may further send a second data packet to the target network device via the second tunnel, the second data packet being a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0012] In the above implementation, the cascading data packets and the non-cascading data packets are forwarded through different tunnels. In this way, the header overhead of the cascading data packets can be reduced, and the overhead caused by distinguishing different types of data packets can be reduced. The decrease in , thereby implementing lossless handover under cascading function.

[0013] In a possible implementation, the source network device may further receive address information of the second tunnel from the target network device.

[0014] In a possible implementation, the source network device may further receive address information of the first tunnel from the target network device.

[0015] In a possible implementation, the data size of the first data packet is X, and the maximum value of X is less than or equal to the smaller value of the first maximum data volume and the second maximum data volume, or the maximum value of X is less than or equal to the smallest value of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and X is a number greater than 0. The first maximum data volume is the maximum data volume of the cascading data packet supported by the source network device, the second maximum data volume is the maximum data volume of the cascading data packet supported by the target network device, and the third maximum data volume is the maximum data volume of the cascading data packet supported by the terminal device.

[0016] According to the above method, the maximum value of the data volume of the first data packet is limited to be equal to or less than the first maximum data volume or the second maximum data volume, thus avoiding the cascading data packet sent by the source network device from exceeding the processing capability of the target network device, improving the processing efficiency of the cascading data packet, and improving the data transmission efficiency.

[0017] In a possible implementation, Y data units are cascaded in the first data packet, and the maximum value of Y is less than or equal to the smaller of the first maximum value and the second maximum value, or the maximum value of Y is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value, and Y is an integer greater than 1. The first maximum value is the maximum value supported by the source network device for the number of data units cascaded to obtain the cascading data packet, the second maximum value is the maximum value supported by the target network device for the number of data units cascaded to obtain the cascading data packet, and the third maximum value is the maximum value supported by the terminal device for the number of data units cascaded to obtain the cascading data packet.

[0018] According to the above method, the maximum value of the number of data units cascaded to obtain the first data packet is limited to be equal to or less than the first maximum value or the second maximum value, thus avoiding the cascading data packet sent by the source network device from exceeding the processing capability of the target network device, improving the processing efficiency of the cascading data packet, and improving the data transmission efficiency.

[0019] In a possible implementation, the source network device may further send a third data packet to the terminal device, where the third data packet is obtained by cascading M data units, where M is an integer greater than 1, and the data in the third data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0020] In a possible implementation, the data size of the third data packet is P, the maximum value of P is less than or equal to the smaller of the first maximum data volume and the third maximum data volume, or the maximum value of P is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and P is a real number greater than 1. The first maximum data volume is the maximum data volume of the cascading data packet supported by the source network device, the second maximum data volume is the maximum data volume of the cascading data packet supported by the target network device, and the third maximum data volume is the maximum data volume of the cascading data packet supported by the terminal device.

[0021] In a possible implementation, the maximum value of M is less than or equal to the smaller of the first maximum value and the third maximum value, or the maximum value of M is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value.

[0022] The first maximum value is the maximum value supported by the source network device for the number of data units cascaded to obtain a cascading data packet, the second maximum value is the maximum value supported by the target network device for the number of data units cascaded to obtain a cascading data packet, and the third maximum value is the maximum value supported by the terminal device for the number of data units cascaded to obtain a cascading data packet.

[0023] In a possible implementation, the source network device may further receive at least one of a second maximum data volume and a second maximum value from the target network device.

[0024] In a possible implementation, the source network device may further receive sequence number number information from the target network device, the sequence number number information indicating the number of sequence numbers being requested, the sequence numbers identifying the data packets.

[0025] In a possible implementation, a sequence number value range is transmitted to the target network device, the sequence number value range including at least one sequence number.

[0026] According to a second aspect, the present application provides a data transmission method. The method is applied to a scenario in which a source network device transfers data of a terminal device to a target network device in a terminal device handover process. An execution subject of the method is the target network device or a module in the target network device. An example in which the target network device is the execution subject is used here for explanation. The method includes the target network device receiving a first data packet from the source network device through a first tunnel, the first data packet being a data packet obtained by cascading at least two data units, the data included in the at least two data units belonging to the same radio bearer or quality of service flow of the terminal device, and the first data packet being a Packet Data Convergence Protocol PDCP layer data packet or a Service Data Adaptation Protocol SDAP layer data packet. The target network device transmits the first data packet to the terminal device.

[0027] In a possible implementation, the target network device may further receive first information from the source network device via the first tunnel and send the first information to the terminal device, where the first information is a first data packet being a cascading data packet.

[0028] In a possible implementation, the target network device may further receive a second data packet and second information from the source network device via the first tunnel, where the second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device. The target network device transmits the second data packet and the second information to the terminal device.

[0029] In a possible implementation, the target network device may further receive a second data packet from the source network device via the second tunnel and transmit the second data packet to the terminal device, where the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0030] In a possible implementation, the data size of the first data packet is X, the maximum value of X is less than or equal to the smaller value of the first maximum data volume and the second maximum data volume, or the maximum value of X is less than or equal to the smallest value of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and X is a real number greater than 0. The first maximum data volume is the maximum data volume of the cascading data packet supported by the source network device, the second maximum data volume is the maximum data volume of the cascading data packet supported by the target network device, and the third maximum data volume is the maximum data volume of the cascading data packet supported by the terminal device.

[0031] In a possible implementation, Y data units are cascaded in the first data packet, and the maximum value of Y is less than or equal to the smaller of the first maximum value and the second maximum value, or the maximum value of Y is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value, and Y is an integer greater than 1. The first maximum value is the maximum value supported by the source network device for the number of data units cascaded to obtain the cascading data packet, the second maximum value is the maximum value supported by the target network device for the number of data units cascaded to obtain the cascading data packet, and the third maximum value is the maximum value supported by the terminal device for the number of data units cascaded to obtain the cascading data packet.

[0032] In a possible implementation, the target network device may further receive at least one of the following information from the source network device: a first maximum data volume, a third maximum data volume, a first maximum value, and a second maximum value, where the first maximum data volume is the maximum data volume of the cascading data packet supported by the source network device, the second maximum data volume is the maximum data volume of the cascading data packet supported by the target network device, the first maximum value is the maximum value of the number of data units cascaded to obtain the cascading data packet supported by the source network device, and the second maximum value is the maximum value of the number of data units cascaded to obtain the cascading data packet supported by the target network device.

[0033] In a possible implementation, the target network device may further receive a plurality of non-cascading data packets from the source network device, where one non-cascading data packet includes one data unit. The target network device sends a fourth data packet to the terminal device, where the fourth data packet is obtained by cascading data units of at least two non-cascading data packets of the plurality of non-cascading data packets.

[0034] In a possible implementation, the data size of the fourth data packet is X2, the maximum value of X2 is less than or equal to the smaller of the second maximum data volume and the third maximum data volume, or the maximum value of X2 is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and X2 is a number greater than 0.

[0035] In a possible implementation, Y2 data units are cascaded in the fourth data packet, and the maximum value of Y2 is less than or equal to the smaller of the second maximum value and the third maximum data volume, or the maximum value of Y2 is less than or equal to the smallest of the first maximum value, the second maximum value and the third maximum value, and Y2 is an integer greater than 1.

[0036] In a possible implementation, the sequence number corresponding to the fourth data packet is within a sequence number value range, the sequence number value range includes at least one sequence number, and the sequence number value range is from a source network device.

[0037] According to a third aspect, the present application provides a data transmission method. The method is applied to a scenario in which a source network device transfers data of a terminal device to a target network device in a terminal device handover process. An execution subject of the method is the source network device or a module in the source network device. An example in which the source network device is the execution subject is used here for explanation. The method includes the source network device sending a fifth data packet to the terminal device, where the fifth data packet is obtained by cascading at least two data units, where the at least two data units include a first data unit and a second data unit. When it is determined that the fifth data packet is not successfully received and the connection between the source network device and the terminal device is disconnected, the source network device sends the first data unit, the second data unit, and a fifth sequence number corresponding to the first data unit and the second data unit to the target network device. The source network device is a network device from which the terminal device is handed over, and the target network device is a network device to which the terminal device is handed over.

[0038] According to a fourth aspect, the present application provides a data transmission method. The method is applied to a scenario in which a source network device transfers data of a terminal device to a target network device in a terminal device handover process. An execution subject of the method is the target network device or a module in the target network device. An example in which the target network device is the execution subject is used here for explanation. The method is applied to a scenario in which the target network device transfers data of a terminal device from a source network device to a target network device in a terminal device handover process. 2nd 1 data unit and,receiving a second data unit and a fifth sequence number corresponding to the first data unit and the second data unit. The data in the first data unit and the data in the second data unit belong to the same radio bearer or quality of service flow of the terminal device. The source network device is a network device from which the terminal device is handed over, and the target network device is a network device to which the terminal device is handed over. The target network device determines a first subsequence number of the first data unit and a second subsequence number of the second data unit. The subsequence number indicates an order of the data unit corresponding to the subsequence number in the at least two data units corresponding to the fifth sequence number. The target network device transmits the first data unit, the first subsequence number, the second data unit, the second subsequence number, and the fifth sequence number to the terminal device.

[0039] In a possible implementation, the first data unit further includes position indication information, where the position indication information indicates whether the first data unit is the last data unit corresponding to the fifth sequence number.

[0040] According to a fifth aspect, the present application further provides a communication device. The communication device has a function for performing the method provided in the first or third aspect. The communication device may be implemented by hardware, or by the hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0041] In a possible implementation, the communication device includes a processor. The processor is configured to support the communication device to perform the corresponding functions of the source network device in the above method. The communication device may further include a memory. The memory may be coupled to the processor, and the memory stores program instructions and data required for the communication device. Optionally, the communication device further includes an interface circuit. The interface circuit is configured to support communication between the communication device and a device such as a terminal device.

[0042] In a possible implementation, the communication device includes corresponding functional modules that are separately configured to perform the steps of the above methods. The functions may be implemented by hardware or by the hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0043] In a possible implementation, the structure of the communication device includes a processing unit and a communication unit. The units may perform corresponding functions in the above method examples. For details, please refer to the method description provided in the first aspect or the third aspect. The details will not be described again here.

[0044] According to a sixth aspect, the present application further provides a communication device. The communication device has a function for performing the method provided in the second or fourth aspect. The communication device may be implemented by hardware, or by the hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0045] In a possible implementation, the communication device includes a processor. The processor is configured to support the communication device to perform the corresponding functions of the target network device in the above method. The communication device may further include a memory. The memory may be coupled to the processor, and the memory stores program instructions and data required for the communication device. Optionally, the communication device further includes an interface circuit. The interface circuit is configured to support communication between the communication device and a device such as a terminal device.

[0046] In a possible implementation, the communication device includes corresponding functional modules that are separately configured to perform the steps of the above methods. The functions may be implemented by hardware or by the hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0047] In a possible implementation, the structure of the communication device includes a processing unit and a communication unit. The units may perform corresponding functions in the above method examples. For details, please refer to the method description provided in the second aspect or the fourth aspect. The details will not be described again here.

[0048] According to a seventh aspect there is provided a communications device including a processor and a memory, the memory storing a computer program or instructions, the processor being configured to execute the computer program or instructions stored in the memory to perform a method of the first aspect, the third aspect or any possible implementation of either one of the first or third aspects.

[0049] According to an eighth aspect there is provided a communications device including a processor and a memory, the memory storing a computer program or instructions, the processor being configured to execute the computer program or instructions stored in the memory to perform a method of the second aspect, the fourth aspect or any possible implementation of either one of the second or fourth aspects.

[0050] According to a ninth aspect, there is provided a communication device including a processor and an interface circuit, and optionally further including a memory. The memory stores computer programs or instructions. The interface circuit is configured to receive signals from a communication device other than the communication device and transmit signals to the processor, or transmit signals from the processor to the communication device other than the communication device. The processor is configured to execute the computer programs or instructions stored in the memory to perform a method in any possible implementation of either the first aspect, the third aspect, or any one of the first or third aspects.

[0051] According to a tenth aspect, there is provided a communication device including a processor and an interface circuit, and optionally further including a memory. The memory stores computer programs or instructions. The interface circuit is configured to receive signals from a communication device other than the communication device and to transmit signals to the processor, or to transmit signals from the processor to a communication device other than the communication device. The processor is configured to execute the computer programs or instructions stored in the memory to perform a method in any possible implementation of either the second aspect, the fourth aspect, or any one of the second aspect or the fourth aspect.

[0052] According to an eleventh aspect, there is provided a computer readable storage medium having stored thereon a computer program or instructions, which, when executed on a computer, can cause the computer to perform the method of any one of the first to fourth aspects and any possible implementations of any one of the first to fourth aspects.

[0053] According to a twelfth aspect, there is provided a computer program product storing computer readable instructions which, when executed on a computer, can cause the computer to perform the method of any one of the first to fourth aspects and any possible implementation of any one of the first to fourth aspects.

[0054] According to a thirteenth aspect, there is provided a chip, the chip including a processor, and possibly a memory, configured to execute computer programs or instructions stored in the memory, such that the chip system performs the method of any one of the first to fourth aspects and any possible implementations of any one of the first to fourth aspects.

[0055] According to a fourteenth aspect, there is provided a communication device including a processor and an interface circuit. The interface circuit is configured to receive a signal from another communication device different from the communication device and to transmit the signal to the processor or to transmit a signal from the processor to a communication device different from the communication device. The processor is configured to execute computer programs or instructions to perform a method of the first aspect, the third aspect, or any possible implementation of any one of the first or third aspects.

[0056] According to a fifteenth aspect, there is provided a communications device including a processor and an interface circuit. The interface circuit is configured to receive a signal from another communications device different from the communications device and to transmit the signal to the processor or to transmit a signal from the processor to a communications device different from the communications device. The processor is configured to execute computer programs or instructions to perform a method in any possible implementation of the second aspect, the fourth aspect, or any one of the second or fourth aspects.

[0057] According to a sixteenth aspect there is provided a communications device including a module configured to implement a method according to the first aspect, the third aspect or any possible implementation of any one of the first or third aspects.

[0058] According to a seventeenth aspect there is provided a communications device including a module configured to implement a method according to the second aspect, the fourth aspect or any possible implementation of any one of the second aspect or the fourth aspect.

[0059] According to an eighteenth aspect, there is provided a communication system, the system including an apparatus according to the fifth aspect (eg, a source network device) and an apparatus according to the sixth aspect (eg, a target network device). [Brief description of the drawings]

[0060] [Figure 1] FIG. 1 is a schematic diagram of a network architecture to which an embodiment of the present application is applied; [Diagram 2] FIG. 2 is a schematic diagram of a handover according to an embodiment of the present application. [Diagram 3] FIG. 2 is a schematic diagram of an Xn handover process according to an embodiment of the present application; [Figure 4] FIG. 2 is a schematic diagram of a protocol stack structure according to an embodiment of the present application; [Diagram 5] 1 is a schematic flowchart of a data transmission method according to an embodiment of the present application; [Figure 6A] FIG. 2 is a schematic diagram of a frame format according to an embodiment of the present application. [Figure 6B] FIG. 2 is a schematic diagram of a frame format according to an embodiment of the present application. [Figure 7(a)] FIG. 2 is a schematic diagram of a structure of a cascading data packet according to an embodiment of the present application; [Figure 7(b)] FIG. 2 is a schematic diagram of a structure of a cascading data packet according to an embodiment of the present application; [Figure 8] FIG. 2 is a schematic diagram of data transmission in a handover process according to an embodiment of the present application; [Figure 9] FIG. 2 is a schematic diagram of data transmission in a handover process according to an embodiment of the present application; [Figure 10] 1 is a schematic flowchart of a data transmission method according to an embodiment of the present application; [Figure 11] 1 is a schematic flowchart of a data transmission method according to an embodiment of the present application; [Figure 12A] 1 is a schematic flowchart of a data transmission method according to an embodiment of the present application; [Figure 12B] 1 is a schematic flowchart of a data transmission method according to an embodiment of the present application; [Figure 13] FIG. 2 is a schematic diagram of data transmission in a handover process according to an embodiment of the present application; [Figure 14] FIG. 1 is a schematic diagram of a structure of a communication device according to an embodiment of the present application. [Figure 15] FIG. 1 is a schematic diagram of a structure of a communication device according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Hereinafter, the embodiments of the present application will be described in detail with reference to the accompanying drawings of the present application.

[0062] The technical solutions in the embodiments of the present application may be applied to various communication systems, such as long term evolution (LTE) systems, NR systems, and next generation communication systems, which are not limited in the present application.

[0063] In the embodiment of the present application, the terminal device may be a device having a wireless transceiver function or a chip that can be disposed in any device. The terminal device may also be called user equipment (UE), access terminal, subscriber unit, subscriber station, mobile station, mobile console, remote station, remote terminal, mobile device, user terminal, wireless communication device, user agent, or user equipment. The terminal device in the embodiment of the present application may be a mobile phone, a tablet computer (Pad), a computer having a wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self driving, etc.

[0064] In the present embodiment, the network device may be a radio access device in various standards. For example, the network device may be a next generation nodeB (gNB) in an NR system, an evolved nodeB (eNB), a radio network controller (RNC), a nodeB (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., a home evolved NodeB or home NodeB (HNB)), a baseband unit (BBU), an access point (AP), a wireless relay node, a wireless backhaul node, or a transmission and reception point (TRP or TP) in a wireless fidelity (Wi-Fi) system. Alternatively, the network device may be a gNB or a transmission point in a 5G (NR) system, one antenna group or a group of antenna panels (including multiple antenna panels) of a base station in a 5G system, or a network node forming a gNB or a transmission point, such as a baseband unit (BBU), or a DU in a central unit-distributed (CU-DU) architecture, etc. The network device may alternatively be a server, a wearable device, an in-vehicle device, etc. For example, a network device in a vehicle-to-everything (V2X) technology can be a roadside unit (RSU).

[0065] In order to facilitate understanding of the embodiments of the present application, the communication system shown in FIG. 1 is first used as an example to describe in detail the communication system to which the embodiments of the present application are applied. FIG. 1 is a schematic diagram of a network architecture to which the embodiments of the present application are applied. As shown in FIG. 1, the network architecture includes a 5G core network (5GC) and a 5G radio access network (NG-RAN). Network communication may be performed between the 5G radio access network and the 5G core network. Nodes in the NG-RAN include a gNB and a next generation eNB (ng-eNB). The gNB is an endpoint that provides user plane protocols and control plane protocols of the NR system, and the ng-eNB is an endpoint that provides user plane protocol stacks and control plane protocol stacks of the E-UTRAN. In addition, an Xn interface is used for connections between the gNBs and the gNBs, between the gNBs and the ng-eNBs, and between the ng-eNBs and the ng-eNBs. The gNB and ng-eNB are connected to the access and mobility management function (AMF) via the NG-C interface. The gNB and ng-eNB are connected to the user plane function (UPF) via the NG-U interface.

[0066] 1 is just an example. The present application may also be applied to other types of network architectures. The examples will not be described one by one here.

[0067] The present application may be applied to a scenario in which a terminal device is handed over from a source cell to a target cell, and may be specifically applied to an Xn handover scenario. Figure 2 is a schematic diagram of a handover according to an embodiment of the present application. During the Xn handover, a target base station to which the target cell belongs and a source base station to which the source cell belongs are in the same AMF region, and an Xn interface exists between the source base station and the target base station.

[0068] Xn handover is of two types: dual active protocol stack (DAPS) handover and non-DAPS handover. non- During a non-DAPS handover, after receiving a radio resource control (RRC) message and performing the handover, the terminal device immediately releases the source base station connection (source link). During a DAPS handover, after receiving an RRC message and performing the handover, the terminal device maintains the source base station connection () and releases the source base station connection after successfully accessing the target base station (i.e., establishing the target base station connection (target link)).

[0069] 3 is a schematic diagram of an Xn handover process according to an embodiment of the present application. The Xn handover process may include the following processes:

[0070] S301: A source base station sends an RRC Reconfiguration message to a terminal device.

[0071] The RRC reconfiguration message is used to deliver measurement control, including measurement objects (intra-frequency / inter-frequency), measurement reporting configuration, etc., to the terminal device.

[0072] S302: The terminal device returns an RRC Reconfiguration Complete message to the source base station.

[0073] S303: The terminal device sends a measurement report to the source base station.

[0074] The terminal device performs measurement based on the received measurement control to obtain a measurement result. After determining that a handover condition is satisfied, the terminal device transmits the measurement result to the source base station by using a measurement report.

[0075] S304: After receiving the measurement report, the source base station makes a handover decision based on the measurement result.

[0076] In the handover decision process, the source base station decides on the target base station.

[0077] S305: The source base station sends a handover request to the target base station in which the selected target cell is located via the Xn link to initiate the handover request.

[0078] S306: The target base station sends a handover request acknowlege to the source base station.

[0079] After receiving the handover request, the target base station performs admission control, and allocates a terminal device instance and transmission resources after admission is granted.

[0080] S307: The source base station sends an RRC reconfiguration message to the terminal device.

[0081] The RRC reconfiguration message instructs the terminal device to be handed over to a target cell of a target base station. During a DAPS handover, the terminal device maintains its connection to the source cell. During a non-DAPS handover, the terminal device immediately disconnects from the source cell.

[0082] S308: The source base station sends a PDCP serial number (SN) to the target base station.

[0083] Optionally, in this case, the source base station may forward data of the terminal device to the target base station.

[0084] S309: Perform a random access procedure between the terminal device and the target base station.

[0085] S310: The terminal device sends an RRC reconfiguration complete message to the target base station. The air interface handover of the terminal device to the target cell is completed.

[0086] S311: The target base station sends a path switch request message to the AMF to notify the terminal device that the serving cell has been changed, where the message carries information such as the target cell identification.

[0087] S312: The AMF sends a path switch request acknowlege message to the target base station.

[0088] S313: The target base station sends a UE CONTEXT RELEASE message to the source base station.

[0089] After receiving the UE context release message, the source base station releases the connection to the terminal device.

[0090] In this application, the structure of the protocol stack between the terminal device and the network device may be shown in FIG. 4 with reference to the above description. In FIG. 4, the architecture of the protocol stack of the 5G system is used as an example for explanation. The protocol stack of the 5G system may include an SDAP layer, a PDCP layer, a radio link control (RLC) layer, and a media access control (MAC) layer. It may be understood that during specific implementation, any protocol layer may include at least one entity configured to implement some or all of the functions of the current protocol layer. This is not limited in this application. The PDCP layer is used as an example. The PDCP entity is located in the PDCP layer, and each PDCP entity may carry data of one radio bearer (RB), such as a signaling radio bearer (SRB) that carries signaling data and a data radio bearer (DRB) that carries service data. In general, a functional entity set for the same radio bearer includes one PDCP entity, at least one RLC entity corresponding to the PDCP entity, at least one MAC entity corresponding to the at least one RLC entity, and at least one PHY entity corresponding to the at least one MAC entity.

[0091] The transmitting end may process an internet protocol (IP) data packet in the order of SDAP layer, PDCP layer, RLC layer, MAC layer, and then PHY layer, and finally deliver the internet protocol data packet to the PHY layer to perform a transmission operation. At each protocol layer, the protocol layer entity may perform processing such as adding a corresponding data packet header (also called a frame head) to a data packet (i.e., a local layer service data unit (SDU) or an upper layer protocol data unit (PDU)) forwarded by an upper layer to obtain a PDU of a current protocol layer. The peer layer of the peer device may remove the packet header of the PDU of the current protocol layer and parse the PDU of the current protocol layer.

[0092] For example, in a 5G system, an example is used in which the transmitting end is a UE and the receiving end is a gNB. When an IP data packet arrives at the SDAP layer of the UE, the SDAP entity located in the SDAP layer uses the IP data packet as an SDAP SDU to perform the function processing of the SDAP layer, adds an SDAP header to the IP data packet to form an SDAP PDU, and then delivers the SDAP PDU to the PDCP layer. The PDCP entity located in the PDCP layer uses the SDAP PDU as a PDCP SDU to perform the function processing of the PDCP layer, and adds a PDCP header to form a PDCP PDU. The PDCP PDU is then delivered to the RLC layer and the MAC layer. Similarly, the RLC layer and the MAC layer separately perform protocol stack processing, add an RLC header and a MAC header, and finally deliver the data packet to the PHY layer to perform a transmission operation. Correspondingly, each peer layer of the gNB subsequently parses the received data packet and delivers the data packet to the upper layer.

[0093] For example, after an IP data packet is processed by each layer, the frame format finally delivered to the PHY layer may be shown in Figure 5, and includes a MAC header, an RLC header, a PDCH header, an SDAP header, an IP data packet, and a message authentication code-integrity (MAC-I). The MAC header, the RLC header, the PDCP header, and the SDAP header include an indication field required when each layer of the receiving end processes the data packet, and may be collectively referred to as a layer 2 (L2) packet header. The MAC-I field is an integrity check code generated by using the integrity protection function of the PDCP layer.

[0094] From the above description, it can be seen that multiple packet header processing and function processing in the protocol layer need to be performed for each IP data packet. When the data transmission rate is relatively high or the data transmission volume is relatively large, the decryption and / or integrity protection function, etc. need to be performed for each IP data packet in the PDCP layer, and the requirements for the data packet processing function of the terminal device and the base station are relatively high. In addition, after each IP data packet is processed, the header overhead of L2 is relatively large, which reduces the transmission performance. Therefore, the present application provides a method for solving the above problems. The following describes the method in detail.

[0095] In the embodiments of the present application, unless there is a special description and logical inconsistency, the terms and / or technical features between different embodiments are consistent and may be mutually referenced, and the technical features in different embodiments may be combined based on their internal logical relationships to form a new embodiment.

[0096] It can be understood that the various numbers in the embodiments of the present application are only used for distinction to facilitate description, and are not used to limit the scope of the embodiments of the present application. The sequential numbers of the above processes do not imply the order of execution, and the order of execution of the processes should be determined based on the internal logic and functions of the processes.

[0097] The network architecture and service scenarios described in the embodiments of the present application are intended to more clearly describe the technical solutions in the embodiments of the present application, and do not constitute limitations on the technical solutions provided in the embodiments of the present application. Those skilled in the art may recognize that with the evolution of network architectures and the emergence of new service scenarios, the technical solutions provided in the embodiments of the present application also apply to similar technical problems.

[0098] 6A and 6B are schematic flowcharts of a data transmission method according to an embodiment of the present application. In the procedure shown in FIG. 6A and FIG. 6B, an example in which a terminal device is handed over from a source network device to a target network device is used for explanation. The method includes the following steps:

[0099] S600 (optional): A source network device receives an IP data packet from a core network device.

[0100] The source network device may receive a number of IP data packets, which are data packets that need to be transmitted to the end device.

[0101] For ease of explanation, in the following description it is assumed that the data in the IP data packets received by the source network device belongs to the same radio bearer or quality of service (QoS) flow of the terminal device.

[0102] S601 (optional): A source network device sends a handover request message to a target network device.

[0103] The handover request message requests a handover of the terminal device to the target network device.

[0104] When the present application is applied to an Xn handover scenario, the source network device may be the source base station in Fig. 2, and the target network device may be the target base station in Fig. 2. Before sending the handover request message, the source network device may further perform other handover procedures. For details, please refer to the procedure in Fig. 3. The details will not be described again here.

[0105] S602 (optional): The target network device sends a handover request acknowledgement message to the source network device.

[0106] In a first possible implementation, the handover request acknowledgement message may include address information of a first tunnel. It is used as an example that the first tunnel corresponds to a first radio bearer or a first quality of service flow. The first tunnel may be configured to carry data belonging to the first radio bearer or the first quality of service flow, and the address information may be an IP address.

[0107] In this implementation, one radio bearer or one quality of service flow corresponds to one tunnel, and the cascading data packets and non-cascading data packets of the radio bearer or quality of service flow are transmitted through the same tunnel. Therefore, for data of the same radio bearer or quality of service flow belonging to a terminal device, the target network device may assign a data forwarding address, i.e., the address information of the tunnel.

[0108] In a second possible implementation, the handover request acknowledgement message may include address information of a first tunnel and address information of a second tunnel, where the first tunnel is used to carry cascading data packets and the second tunnel is used to carry non-cascading data packets, where the data in the cascading data packets and the data in the non-cascading data packets both belong to a first radio bearer or a first quality of service flow.

[0109] In this implementation, one radio bearer or one quality of service flow corresponds to two tunnels, and cascading data packets and non-cascading data packets are transmitted through different tunnels. Therefore, for data of the same radio bearer or quality of service flow belonging to a terminal device, the target network device may allocate two data forwarding addresses (i.e., address information of the tunnels).

[0110] In this embodiment of the present application, in the process of the terminal device being handed over to the target network device, in a possible implementation, the source network device may directly forward the IP data packet to the terminal device. In another possible implementation, the source network device may forward the IP data packet to the target network device, and the target network device forwards the IP data packet to the terminal device. Furthermore, in the handover process, if the source network device does not receive a corresponding acknowledgement (ACK) message for the IP data packet sent by the source network device to the terminal device, the IP data packet may be forwarded to the terminal device by using the target network device. The following describes the process of the source network device forwarding the IP data packet separately.

[0111] S603: The source network device performs a cascade connection process on at least two data units to obtain a first data packet.

[0112] Data in the at least two data units travels from a core network device, and the data contained in the at least two data units belongs to the same radio bearer or quality of service flow of the terminal device.

[0113] The source network device may perform a cascade connection process on at least two data units at the SDAP layer, or may perform a cascade connection process on at least two data units at the PDCP layer.

[0114] When the cascading function is performed at the SDAP layer, the first data packet may be an SDAP layer data packet, and the data unit may be an IP data packet, where the SDAP layer data packet may be an SDAP PDU for the SDAP layer and a PDCP SDU for the PDCP layer.

[0115] The SDAP layer entity of the source network device may cascade at least two data units (e.g., IP data packets) into one SDAP layer data packet (e.g., SDAP PDU). The frame format of the data packet (e.g., MAC subPDU) finally delivered to the physical layer may be shown in FIG. 7(a) and includes a MAC header, an RLC header, a PDCP header, a cascaded SDAP header, IP header 0, IP data packet 0, IP header 1, IP data packet 1, IP header 2, IP data packet 2, ..., and a MAC-I. The cascaded SDAP header may include a field such as a field indicating the number of cascaded IP data packets to instruct the receiving end to correctly perform the cascade splitting function.

[0116] With reference to the above description, it can be seen that in an SDAP layer data packet in which multiple data units are cascaded, multiple IP data packets share one SDAP header, and it is not necessary to configure one SDAP header for each data unit in the SDAP layer data packet, so the header overhead can be reduced.

[0117] When the cascading function is performed in the PDCP layer, the first data packet may be a PDCP layer data packet, and the data unit may be a SDAP layer data packet, where the PDCP layer data packet may be a PDCP PDU for the PDCP layer and an RLC SDU for the RLC layer.

[0118] The PDCP layer entity of the source network device may cascade at least two data units (e.g., PDCP SDUs) into one PDCP layer data packet (e.g., PDCP PDU). The frame format of the data packet (e.g., MAC subPDU) finally delivered to the physical layer may be shown in FIG. 7(b) and includes a MAC header, an RLC header, a cascaded PDCP header, an SDAP header, an IP header 0, an IP data packet 0, an SDAP header, an IP header 1, an IP data packet 1, an SDAP header, an IP header 2, an IP data packet 2, ..., and a MAC-I. The cascaded PDCP header may include a field such as a field indicating the number of cascaded IP data packets to instruct the receiving end to correctly perform the cascade splitting function.

[0119] With reference to the above description, it can be seen that in a PDCP layer data packet in which multiple data units are cascaded, multiple SDAP layer data packets share one PDCP header, and it is not necessary to configure one PDCP header for each data unit in the PDCP layer data packet, thus reducing the header overhead.

[0120] S604: The source network device sends a first data packet to the target network device via the first tunnel.

[0121] In implementation, the first radio bearer or the first quality of service flow corresponds to one tunnel, i.e., corresponds to the first tunnel. If the data in the first data packet belongs to the first radio bearer or the first quality of service flow, the source network device may further send first information to the target network device through the first tunnel, where the first information indicates that the first data packet is a cascading data packet.

[0122] In this embodiment of the present application, the cascading data packet is a data packet in which multiple IP data packets are cascaded at the SDAP layer, and the multiple IP data packets cascaded in the cascading data packet share one cascaded SDAP packet header. Alternatively, the cascading data packet is a data packet in which multiple PDCP SDUs are cascaded at the PDCP layer, and the multiple cascaded PDCP SDUs in the cascading data packet share one cascaded PDCP packet header.

[0123] Correspondingly, a non-cascading data packet is a data packet that includes one IP data packet, and does not cascade multiple IP data packets at the SDAP layer and does not cascade multiple PDCP SDUs at the PDCP layer.

[0124] The first information may be located in the first data packet. For example, the first information may be located in a PDCP header or an SDAP header of the first data packet. Alternatively, the first information and the first data packet may be independent of each other. The first information may be located in a message other than the first data packet, for example, an Xn message. This is not limited in this embodiment of the present application.

[0125] In this embodiment of the present application, the source network device may further assign a sequence number (SN) to the first data packet. The sequence number may be a PDCP SN. The sequence number may identify the data packet. To ensure that the transmitting end transmits data in order, the PDCP entity at the transmitting end maintains a SN for each data packet. When transmitting data, the transmitting end transmits the data in ascending order of the SNs of the data packets. Correspondingly, the PDCP entity at the receiving end also maintains the same SN for each data packet to ensure that the data packets are delivered to the upper layer in ascending order of the SNs of the data packets.

[0126] In this implementation, the cascading data packets and the non-cascading data packets are transmitted through the first tunnel. Optionally, S605 is further included.

[0127] S605: The source network device sends the second data packet and the second information to the target network device via the first tunnel.

[0128] The second data packet is a non-cascading data packet, and the second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0129] For example, as shown in FIG. 8, the data units acquired by the source network device are data unit 1 to data unit 8, respectively. The source network device has sent data unit 1, data unit 2, and data unit 6 to the terminal device, and data unit 3 to data unit 5 have not been sent to the terminal device. In the process of the terminal device being handed over to the target network device, the source network device may cascade data unit 3 to data unit 5 to acquire one data packet, and send the data packet to the target network device through the first tunnel. The target network device forwards the data packet in which data unit 3 to data unit 5 are cascaded to the terminal device. The source network device may further encapsulate data unit 7 and data unit 8 into a non-cascading data packet, and send the non-cascading data packet to the target network device through the first tunnel.

[0130] In the above implementation, the cascading data packets and the non-cascading data packets of the same radio bearer or quality of service flow are forwarded through a public tunnel (e.g., the first tunnel), and the type of the data packet (cascading data packet or non-cascading data packet) is further indicated. In this way, the header overhead of the cascading data packets can be reduced, and lossless handover under the cascading connection function can be implemented.

[0131] In another implementation, the first radio bearer or the first quality of service flow corresponds to two tunnels, for example, a first tunnel and a second tunnel. When the first tunnel is used to transmit cascading data packets and the second tunnel is used to transmit non-cascading data packets, the method may further include S606.

[0132] S606 (optional): The source network device sends a second data packet to the target network device through the second tunnel.

[0133] Similarly, the source network device may further assign a sequence number to the second data packet, where the sequence number may be a PDCP SN. Assume that the sequence number of the first data packet is a first SN, the sequence number of the second data packet is a second SN, and the first SN is different from the second SN.

[0134] For example, as shown in FIG. 9, the data units acquired by the source network device are data unit 1 to data unit 8, respectively. The source network device transmits data unit 1, data unit 2, and data unit 6 to the terminal device, but data unit 3 to data unit 5 have not been transmitted to the terminal device. In the process of the terminal device being handed over to the target network device, the source network device may cascade data unit 3 to data unit 5 to acquire one data packet, and transmit the data packet to the target network device through the first tunnel. The target network device forwards the data packet in which data unit 3 to data unit 5 are cascaded to the terminal device. The source network device may further encapsulate data unit 7 and data unit 8 into a non-cascading data packet, and transmit the non-cascading data packet to the target network device through the second tunnel.

[0135] The cascading data packets and the non-cascading data packets are forwarded through different tunnels. In this way, the overhead of the cascading data packets can be reduced, and the overhead caused by distinguishing different types of data packets can be reduced. The decrease in , thereby implementing lossless handover under cascading function.

[0136] S607: The target network device receives a first data packet from the source network device via the first tunnel.

[0137] In implementation, when both the cascading data packets and the non-cascading data packets are transmitted through the first tunnel, the target network device may further receive the first information from the source network device through the first tunnel.

[0138] In implementation, the target network device may further receive the second data packet and the second information from the source network device via the first tunnel.

[0139] In other implementations, when the cascading data packets are transmitted through a first tunnel and the non-cascading data packets are transmitted through a second tunnel, the target network device may further receive the second data packets from the source network device through the second tunnel.

[0140] S608: The target network device sends a first data packet to the terminal device.

[0141] In implementation, when the target network device receives the first information, the target network device may further send the first information to the terminal device. After receiving the first data packet, the terminal device may perform a cascade connection separation operation on the first data packet. The specific process is not described again.

[0142] Optionally, when the target network device receives the second data packet, the target network device may further transmit the second data packet to the terminal device.

[0143] S609 (optional): The source network device sends a third data packet to the terminal device.

[0144] The third data packet may be a cascading data packet or a non-cascading data packet, which is not limited in this embodiment of the present application. The data in the third data packet and the data in the first data packet may belong to the same radio bearer or quality of service flow.

[0145] In this embodiment of the present application, in order to avoid that the target network device cannot process the cascading data packet due to the mismatched capabilities of the source network device and the target network device in the handover process, the source network device and the target network device may further negotiate the number of data units that can be cascaded in one cascading data packet and / or the maximum data volume of the cascading data packet. For details, please refer to the following process.

[0146] 10 is a schematic flowchart of a data transmission method according to an embodiment of the present application. In the procedure shown in FIG. 10, an example in which a terminal device is handed over from a source network device to a target network device is used for explanation. The method includes the following steps:

[0147] S1001 (optional): A source network device sends a handover request message to a target network device.

[0148] The handover request message requests a handover of the terminal device to the target network device, and may include at least one of first capability information of the source network device and third capability information of the terminal device.

[0149] The first capability information may indicate at least one of the following information: A first maximum data volume, specifically, the maximum data volume of the cascading data packet supported by the source network device, for example, the first maximum data volume is 500KB; A first minimum data volume, specifically, the minimum data volume of the cascading data packet supported by the source network device, for example, the first minimum data volume is 100KB; A first maximum value, specifically, the maximum value of the number of data units supported by the source network device that are cascaded to obtain a cascading data packet; and A first minimum value, specifically, the minimum value of the number of data units supported by the source network device that is cascaded to obtain a cascading data packet.

[0150] The third capability information may indicate at least one of the following information: A third maximum data volume, specifically, the maximum data volume of the cascading data packet supported by the terminal device; A third minimum data volume, specifically, the minimum data volume of a cascading data packet supported by the terminal device; A third maximum value, specifically, the maximum value of the number of data units supported by the terminal device that are cascaded to obtain a cascading data packet; and A third minimum value, specifically, the minimum value of the number of data units supported by the terminal device that are cascaded to obtain a cascading data packet.

[0151] In this embodiment of the present application, before sending the handover request message, the source network device may further perform other handover procedures, for details, please refer to the procedures in Figure 3, and the details will not be described again here.

[0152] S1002 (optional): The target network device sends a handover request acknowledgement message to the source network device.

[0153] In addition to the information described in S602, the handover request acknowledgment message may further include at least one of the following information: second capability information of the target network device and a second lifetime, where the second lifetime is used for timing by the cascading timer, and the source network device performs a cascading operation when the cascading timer expires.

[0154] The second capability information may indicate at least one of the following information: A second maximum data volume, specifically, the maximum data volume of the cascading data packet supported by the target network device; A second minimum data volume, specifically, the minimum data volume of the cascading data packet supported by the target network device; A second maximum value, specifically, the maximum value of the number of data units supported by the target network device that are cascaded to obtain the cascading data packet; and A second minimum value, specifically, the minimum value of the number of data units supported by the target network device that is cascaded to obtain the cascading data packet.

[0155] S1003: A source network device generates a first data packet.

[0156] The source network device may determine a maximum data volume of the first data packet and / or a maximum number of data units included in the first data packet based on at least one of the first capability information, the second capability information, and the third capability information. The source network device may further determine a minimum data volume of the first data packet and / or a minimum number of data units included in the first data packet based on at least one of the first capability information, the second capability information, and the third capability information.

[0157] Similarly, the source network device may determine a maximum data volume of the third data packet and / or a maximum number of data units included in the third data packet based on at least one of the first capability information, the second capability information, and the third capability information. The source network device may further determine a minimum data volume of the third data packet and / or a minimum number of data units included in the third data packet based on at least one of the first capability information, the second capability information, and the third capability information.

[0158] For example, assume that the data size of the first data packet is X, where X is a real number greater than zero.

[0159] In a possible implementation, the maximum value of X is less than or equal to the smaller of the first maximum data volume and the second maximum data volume. In another possible implementation, the maximum value of X is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume.

[0160] For example, the first largest data volume is 500KB, the second largest data volume is 450KB, and the third largest data volume is 400KB, in which case the maximum value of X may be the smaller of 500KB and 450K, i.e., 450KB, or the maximum value of X may be the smallest of 500KB, 450KB, and 400KB, i.e., 400KB.

[0161] For example, assume that the number of data units cascaded in the first data packet is Y, where Y is an integer greater than one.

[0162] In a possible implementation, the maximum value of Y is less than or equal to the smaller of the first maximum value and the second maximum value. In another possible implementation, the maximum value of Y is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value.

[0163] For example, the first maximum value is 30, the second maximum value is 25, and the third maximum value is 20. In this case, the maximum value of Y may be the smaller of 30 and 25, i.e., 25. Alternatively, the maximum value of Y may be the smallest of 30, 25, and 20, i.e., 20.

[0164] According to the above method, by exchanging capability information, the source network device and the target network device may negotiate the capability of processing the cascading data packet. In this way, the cascading data packet sent by the source network device is avoided from exceeding the processing capability of the target network device, the processing efficiency of the cascading data packet is improved, and the data transmission efficiency is improved.

[0165] In this embodiment of the present application, the protocol layer entity of the source network device may perform data packet cascading based on a cascading timer, which may be specifically as follows:

[0166] When receiving the first data unit, the source network device starts a cascading timer, where the cascading timer has a specified duration. The cascading function is performed for data units arriving at the SDAP layer or the PDCP layer within the specified duration, so as to cascade the data units into the same data packet. The cascading timer is a timer used to measure a specific duration for which the cascading function is performed.

[0167] The specified lifetime may be one of a first lifetime and a second lifetime, the first lifetime being a lifetime determined independently by the source network device, and the second lifetime being a lifetime indicated to the source network device by the target network device.

[0168] S1004: The source network device sends a first data packet to the target network device.

[0169] For a specific process of the source network device sending the cascading data packet to the target network device, please refer to the procedure shown in Figure 5. The details will not be described again here.

[0170] S1005 (optional): The source network device generates a third data packet.

[0171] An example in which the third data packet is a cascading data packet is used here for explanation. The source network device may determine a maximum data volume of the third data packet and / or a maximum value of a data unit included in the third data packet based on at least one of the first capability information, the second capability information, and the third capability information. The source network device may further determine a minimum data volume of the third data packet and / or a minimum value of a data unit included in the third data packet based on at least one of the first capability information, the second capability information, and the third capability information.

[0172] For example, assume that the data size of the third data packet is P, where P is a real number greater than 0.

[0173] In a possible implementation, the maximum value of P is less than or equal to the smaller of the first maximum data volume and the third maximum data volume. In another possible implementation, the maximum value of P is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume.

[0174] For example, the first largest data volume is 500KB, the second largest data volume is 450KB, and the third largest data volume is 400KB. In this case, the maximum value of P may be the smaller of 500KB and 400K, i.e., 400KB. Alternatively, the maximum value of P may be the smallest of 500KB, 450KB, and 400KB, i.e., 400KB.

[0175] For example, assume that the number of data units cascaded in the third data packet is M, where M is an integer greater than one.

[0176] In a possible implementation, the maximum value of M is less than or equal to the smaller of the first maximum value and the third maximum value. In another possible implementation, the maximum value of M is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value.

[0177] For example, the first maximum value is 30, the second maximum value is 25, and the third maximum value is 20. In this case, the maximum value of M may be the smaller of 30 and 20, i.e., 20. Alternatively, the maximum value of M may be the smallest of 30, 25, and 20, i.e., 20.

[0178] According to the above method, the source network device performs data packet cascading connection based on the capability information of the terminal device, so as to avoid the cascading data packets sent by the source network device exceeding the processing capability of the terminal device, improve the processing efficiency of the cascading data packets, and improve the data transmission efficiency.

[0179] S1006: The source network device sends a third data packet to the terminal device.

[0180] How the source network device specifically transmits the cascading data packets to the terminal device is not limited in this embodiment of the present application, and the details will not be described again here.

[0181] Furthermore, the source network device may further assign a sequence number to the third data packet, and the sequence number of the third data packet may be the third SN. Assume that the sequence number of the first data packet is the first SN, and the first SN is different from the third SN.

[0182] In this embodiment of the present application, when a source network device sends a non-cascading data packet to a target network device, the target network device may cascade the non-cascading data packet and send a cascading data packet to a terminal device. To ensure that the sequence numbers of data packets are unique, the source network device may assign sequence numbers to the cascading data packets generated by the target network device. For details, please refer to the following process.

[0183] 11 is a schematic flowchart of a data transmission method according to an embodiment of the present application. In the procedure shown in FIG. 11, an example in which a terminal device is handed over from a source network device to a target network device is used for explanation. The method includes the following steps:

[0184] S1101 (optional): A source network device sends a handover request message to a target network device.

[0185] The handover request message requests the terminal device to hand over to the target network device. For information contained in the handover request message, please refer to the description in the procedure shown in Figure 5 or Figure 10. Details will not be described again here.

[0186] In this embodiment of the present application, before sending the handover request message, the source network device may further perform other handover procedures, for details, please refer to the procedures in Figure 3, and the details will not be described again here.

[0187] S1102 (optional): The target network device sends a handover request acknowledgement message to the source network device.

[0188] In addition to the information described in S602 and S1002, the handover request acknowledgement message may further include sequence number information, which indicates the number of sequence numbers being requested, and the sequence numbers identify data packets. For example, the sequence numbers may be PDCP SNs.

[0189] S1103: The source network device sends the sequence number value range to the target network device.

[0190] The sequence number value range includes at least one sequence number. For example, a sequence number value range of 50 to 100 indicates that the sequence numbers that may be assigned by the target network device are from 50 to 100. The number of sequence numbers included in the sequence number value range may be less than or equal to the number of sequence numbers requested by the sequence number count information.

[0191] Furthermore, to ensure that the sequence numbers assigned by the source network device and the sequence numbers assigned by the target network device are consistent, the source network device no longer selects sequence numbers from a sequence number value range when assigning sequence numbers.

[0192] S1104: The source network device sends a plurality of non-cascading data packets to the target network device.

[0193] The data in the non-cascading data packet arrives from the core network, and one non-cascading data packet contains one data unit.

[0194] S1105: The target network device sends a fourth data packet to the terminal device, where the fourth data packet is obtained by cascading at least two data units of the multiple non-cascading data packets.

[0195] The sequence number corresponding to the fourth data packet is within the sequence number value range.

[0196] In this embodiment of the present application, the data size of the fourth data packet is X2. In a possible implementation, the maximum value of X2 is equal to or less than the smaller value of the second maximum data volume and the third maximum data volume. In another possible implementation, the maximum value of X2 is equal to or less than the smallest value of the first maximum data volume, the second maximum data volume, and the third maximum data volume, where X2 is a real number greater than 0.

[0197] Y2 data units are cascaded in the fourth data packet. In a possible implementation, the maximum value of Y2 is less than or equal to the smaller of the second maximum value and the third maximum value. In another possible implementation, the maximum value of Y2 is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value, where Y2 is an integer greater than 1.

[0198] Optionally, when sequence numbers in the sequence number value range are about to be exhausted for allocation, the target network device may further request the source network device to reallocate sequence numbers. For example, the target network device may perform the following steps:

[0199] S1106: The target network device sends a sequence number allocation request message to the source network device to request allocation of a sequence number.

[0200] The sequence number assignment request message may include at least one of the following: the number of sequence numbers requested to be assigned, and the number of remaining sequence numbers to be deallocated (e.g., of the last 100 sequence numbers to be assigned, 20 sequence numbers remain unassigned).

[0201] Furthermore, when the source network device receives the sequence number allocation request message, the number of sequence numbers assigned to the target network device may be less than or equal to the number of sequence numbers requested to be assigned by the sequence number allocation request message.

[0202] The embodiment of the present application further provides a method that can be applied to a scenario in which a terminal device supports processing cascading data packets, but a target network device does not support processing cascading data packets, as will be described in detail below.

[0203] 12A and 12B are schematic flowcharts of a data transmission method according to an embodiment of the present application. In the procedure shown in FIG. 12A and FIG. 12B, an example in which a terminal device is handed over from a source network device to a target network device is used for explanation. The method includes the following steps:

[0204] S1201 (optional): A source network device sends a handover request message to a target network device.

[0205] The handover request message requests the terminal device to hand over to the target network device. For information contained in the handover request message, please refer to the description in the procedure shown in Figure 5 or Figure 10. Details will not be described again here.

[0206] In this embodiment of the present application, before sending the handover request message, the source network device may further perform other handover procedures, for details, please refer to the procedures in Figure 3, and the details will not be described again here.

[0207] S1202 (optional): The target network device sends a handover request acknowledgement message to the source network device.

[0208] The handover request acknowledgement message may include an RRC reconfiguration message, which indicates to the terminal device that it is to be handed over to the target cell of the target network device.

[0209] S1203: The source network device sends a fifth data packet to the terminal device.

[0210] A fifth data packet is obtained by cascading at least two data units, the at least two data units including a first data unit and a second data unit. The sequence number of the fifth data packet is a fifth sequence number. The data in the data units of the fifth data packet belong to the same radio bearer or quality of service flow of the terminal device. In other words, the data in the first data unit and the data in the second data unit belong to the same radio bearer or quality of service flow of the terminal device.

[0211] S1204: The source network device sends an RRC reconfiguration message to the terminal device.

[0212] Upon receiving the RRC reconfiguration message, the terminal device detaches from the source network device, i.e., disconnects the source link.

[0213] If the source network device determines that the terminal device cannot receive the fifth data packet, the source network device may forward the data in the fifth data packet to the target network device. The method by which the source network device determines that the terminal device cannot receive the fifth data packet is not limited in this application. For example, the source network device receives a negative acknowledgment (NACK) corresponding to the fifth data packet. In this case, the source network device may determine that the terminal device has failed to receive the fifth data packet.

[0214] When the source network device forwards the data in the fifth data packet to the target network device, because the target network device does not support processing cascading data packets, the source network device sends the data units cascaded in the fifth data packet separately to the target network device.

[0215] Specifically, the first data unit and the second data unit are used as an example. The source network device performs the following steps:

[0216] S1205: The source network device sends the first data unit, the second data unit, and the fifth sequence number to the target network device.

[0217] In this embodiment of the present application, the source network device may assign a first temporary sequence number to the first data unit and a second temporary sequence number to the second data unit, the first temporary sequence number indicating an order of the first data unit within the at least two data units corresponding to the fifth sequence number, and the second temporary sequence number indicating an order of the second data unit within the at least two data units corresponding to the fifth sequence number.

[0218] S1206: The target network device receives the first data unit, the second data unit, and the fifth sequence number from the source network device.

[0219] The target network device may determine an order of the first data unit and the second data unit within the at least two data units corresponding to the fifth sequence number based on the first temporary sequence number and the second temporary sequence number.

[0220] S1207: The target network device sends the first data unit, the first subsequence number corresponding to the first data unit, the second data unit, the second subsequence number corresponding to the second data unit, and the fifth sequence number to the terminal device.

[0221] The subsequence numbers indicate an order of the data unit corresponding to the subsequence number within the at least two data units, e.g., a first subsequence number indicates an order of a first data unit within the at least two data units corresponding to a fifth sequence number, and a second subsequence number indicates an order of a second data unit within the at least two data units corresponding to the fifth sequence number.

[0222] The first data unit further includes position indication information, and the position indication information in the first data unit indicates whether the first data unit is the last data unit corresponding to the fifth sequence number. Similarly, the second data unit further includes position indication information, and the position indication information in the second data unit indicates whether the second data unit is the last data unit corresponding to the fifth sequence number.

[0223] S1208: The terminal device receives a first data unit, a first subsequence number corresponding to the first data unit, a second data unit, a second subsequence number corresponding to the second data unit, and a fifth sequence number.

[0224] The terminal device may determine an order of the first data unit and the second data unit based on the first subsequence number, the second subsequence number, and the fifth sequence number to reorder the first data unit and the second data unit, and then deliver the first data unit and the second data unit in order to an upper layer of the terminal device for processing. The upper layer may be an IP layer or a transmission control protocol (TCP) layer.

[0225] For example, Fig. 13 is a schematic diagram of handover according to an embodiment of the present application with reference to the above description. In Fig. 13, a source network device sends data packets with sequence numbers 1 to 5, respectively, to a terminal device. All data packets are successfully received by the terminal device except for a data packet with sequence number 3, which the terminal device fails to receive. It is assumed that three data packets are cascaded in the data packet with sequence number 3, and the three data units are data units 1 to 3, respectively.

[0226] When the terminal device is handed over to the target network device, the source network device transmits data units 1 to 3 to the target network device separately, and also transmits sequence number 3. target The temporary sequence numbers assigned by the source network device to data units 1 through 3, respectively, are 3-1, 3-2, and 3-3.

[0227] When receiving data units 1 to 3, the target network device may assign subsequence numbers to data units 1 to 3 separately. For example, the assigned subsequence numbers are 3001, 3002, and 3003. The target network device may transmit data units 1 to 3, the subsequence numbers of the data units, and the sequence number 3 corresponding to data units 1 to 3 to the terminal device. Each data unit may further correspond to one piece of location indication information.

[0228] After receiving the data and information, the terminal device may determine, based on sequence number 3, that data units 1 to 3 are located between the data packet with sequence number 2 and the data packet with sequence number 4. The terminal device may further determine the order of data units 1 to 3 based on the subsequence numbers of the data units. Thus, the terminal device may deliver the data packets in order.

[0229] According to the method provided in this embodiment of the present application, the target network device further assigns a subsequence number to each data unit, so that the order of multiple data packets corresponding to a sequence number can be determined based on the subsequence numbers, thereby ensuring that the multiple data packets corresponding to a sequence number can be delivered in order.

[0230] The above embodiments may be implemented separately or in combination with each other. In the above content, the differences between the embodiments are described in detail in different embodiments. Contents other than the differences between different embodiments can be referred to each other. It should be understood that the step numbers in the flowcharts described in the embodiments of the present application are only examples of execution procedures and do not constitute limitations on the execution order of the steps. In the embodiments of the present application, there is no strict execution order between steps that are independent of each other in chronological order. Moreover, not all steps shown in the flowcharts are required steps. Some steps may be added to or deleted from the flowcharts according to actual requirements.

[0231] In the above embodiments provided in the present application, the methods provided in the embodiments of the present application are described separately from the viewpoint of the interaction between devices. The steps performed by the access network device may alternatively be separately performed by different communication devices. For example, the first device is configured to receive a first signal and initiate random access, and the second device is configured to process the first signal by using the energy provided by the first signal. In other words, the first device and the second device together complete the steps performed by the access network device in the embodiments of the present application. The specific division manner is not limited in the present application. Optionally, the energy extraction from the first signal may alternatively be performed by a third device. When the network architecture includes one or more distributed units (DU), one or more centralized units (CU), and one or more radio frequency units (RU), the steps performed by the access network device may be separately performed by the DU, the CU, and the RU.

[0232] In order to implement the functions of the methods provided in the embodiments of the present application, the access network device, the terminal device, or the above-mentioned communication device may include a hardware structure and / or a software module, and may implement the above-mentioned functions in the form of a hardware structure, a software module, or a combination of a hardware structure and a software module. Whether a particular function among the above-mentioned functions is implemented by using a hardware structure, a software module, or a combination of a hardware structure and a software module depends on the specific application and design constraints of the technical solution.

[0233] In the embodiment of the present application, the module division is an example and is merely a logical division of functions. In actual implementation, other division manners may be used. Furthermore, the functional modules in the embodiment of the present application may be integrated into one processor, may exist physically alone, or two or more modules may be integrated into one module. The integrated module may be implemented in the form of hardware or in the form of a software functional module.

[0234] Similar to the above concept, the embodiment of the present application further provides a communication device, as shown in Fig. 14. The communication device 1400 may be the source base station in Fig. 2, configured to implement the method of the source network device in the above method embodiment. Alternatively, the communication device may be the target base station in Fig. 2, configured to implement the method corresponding to the target network device in the above method embodiment. For specific functions, please refer to the description of the above method embodiment.

[0235] Specifically, the communication device 1400 may include a processing unit 1401 and a communication unit 1402. In this embodiment of the present application, the communication unit may also be referred to as a transceiver unit, and may include a transmitting unit and / or a receiving unit, respectively configured to perform the transmitting and receiving steps of a network device or a terminal device in the above method embodiment. The following will describe in detail the communication device provided in the embodiment of the present application with reference to Figures 12A to 13.

[0236] In some possible implementations, the operations and functions of the source network device in the above method embodiments may be implemented by using the communication device 1400, for example, the methods performed by the source network device in the embodiments shown in Figures 6A to 12B. For example, the communication device 1400 may be a component (e.g., a chip or circuit) used in the source network device, or may be a chip or chipset in the source network device, or a portion of a chip configured to perform the relevant method functions. The communication unit 1402 may be configured to perform the receiving or transmitting operations performed by the source network device in the embodiments shown in Figures 6A to 12B. The processing unit 1401 may be configured to perform operations other than the receiving and transmitting operations performed by the source network device in the embodiments shown in Figures 6A to 12B.

[0237] In a possible implementation, the processing unit is configured to perform cascading processing on at least two data units to obtain a first data packet, the data included in the at least two data units belonging to the same radio bearer or quality of service flow of the terminal device, the first data packet being a Packet Data Convergence Protocol PDCP layer data packet or a Service Data Adaptation Protocol SDAP layer data packet, and the communication unit is configured to transmit the first data packet to the target network device via the first tunnel.

[0238] In a possible implementation, the communication unit is further configured to send first information to the target network device via the first tunnel, the first information indicating that the first data packet is a cascading data packet.

[0239] In a possible implementation, the communication unit is further configured to transmit a second data packet and second information to the target network device via the first tunnel, where the second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0240] In a possible implementation, the communication unit is further configured to transmit a second data packet to the target network device via a second tunnel, where the second data packet is a non-cascading data packet and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0241] In a possible implementation, the data size of the first data packet is X, and the maximum value of X is less than or equal to the smaller of the first maximum data volume and the second maximum data volume, or the maximum value of X is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and X is a number greater than 0.

[0242] The first maximum data volume is a maximum data volume of the cascading data packet supported by a source network device, the second maximum data volume is a maximum data volume of the cascading data packet supported by a target network device, and the third maximum data volume is a maximum data volume of the cascading data packet supported by a terminal device.

[0243] In a possible implementation, Y data units are cascaded in the first data packet, and the maximum value of Y is less than or equal to the smaller of the first maximum value and the second maximum value, or the maximum value of Y is less than or equal to the smallest of the first maximum value, the second maximum value and the third maximum value, and Y is an integer greater than 1.

[0244] The first maximum value is the maximum value supported by the source network device for the number of data units cascaded to obtain a cascading data packet, the second maximum value is the maximum value supported by the target network device for the number of data units cascaded to obtain a cascading data packet, and the third maximum value is the maximum value supported by the terminal device for the number of data units cascaded to obtain a cascading data packet.

[0245] In a possible implementation, the communication unit is further configured to transmit a third data packet to the terminal device, the third data packet being obtained by cascading M data units, M being an integer greater than 1, and the data in the third data packet and the data in the first data packet belonging to the same radio bearer or quality of service flow of the terminal device.

[0246] In a possible implementation, the data size of the third data packet is P, the maximum value of P is less than or equal to the smaller of the first maximum data volume and the third maximum data volume, or the maximum value of P is less than or equal to the smallest of the first maximum data volume, the second maximum data volume, and the third maximum data volume, and P is a real number greater than 1.

[0247] The first maximum data volume is the maximum data volume of the cascading data packet supported by the source network device, the second maximum data volume is the maximum data volume of the cascading data packet supported by the target network device, and the third maximum data volume is the maximum data volume of the cascading data packet supported by the terminal device.

[0248] In a possible implementation, the maximum value of M is less than or equal to the smaller of the first maximum value and the third maximum value, or the maximum value of M is less than or equal to the smallest of the first maximum value, the second maximum value, and the third maximum value.

[0249] The first maximum value is the maximum value supported by the source network device for the number of data units cascaded to obtain a cascading data packet, the second maximum value is the maximum value supported by the target network device for the number of data units cascaded to obtain a cascading data packet, and the third maximum value is the maximum value supported by the terminal device for the number of data units cascaded to obtain a cascading data packet.

[0250] In some possible implementations, the operations and functions of the target network device in the above method embodiments may be implemented by using the communication device 1400, for example, the method performed by the target network device in the embodiments shown in Figures 6A to 12B. For example, the communication device 1400 may be a component (e.g., a chip or circuit) used in the target network device, or may be a chip or chipset in the target network device, or a portion of a chip configured to perform the associated method functions. The communication unit 1402 may be configured to perform the receiving or transmitting operations performed by the target network device in the embodiments shown in Figures 6A to 12B. The processing unit 1401 may be configured to perform operations other than the receiving and transmitting operations performed by the target network device in the embodiments shown in Figures 6A to 12B.

[0251] In a possible implementation, the processing unit is configured to receive a first data packet from a source network device by using the communication unit via a first tunnel, the first data packet being a data packet obtained by cascading at least two data units, where data contained in the at least two data units belong to a same radio bearer or quality of service flow of the terminal device, and the first data packet being a Packet Data Convergence Protocol PDCP layer data packet or a Service Data Adaptation Protocol SDAP layer data packet.

[0252] The processing unit is configured to transmit the first data packet to the terminal device by using the communication unit.

[0253] In a possible implementation, the communication unit is further configured to receive first information from the source network device via the first tunnel and to transmit the first information to the terminal device, where the first information indicates that the first data packet is a cascading data packet.

[0254] In a possible implementation, the communication unit is further configured to receive a second data packet and second information from the source network device via the first tunnel and to transmit the second data packet and the second information to the terminal device, where the second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0255] In a possible implementation, the communication unit is further configured to receive a second data packet from the source network device via the second tunnel and to transmit the second data packet to the terminal device, the second data packet being a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

[0256] In a possible implementation, the communication unit is further configured to receive a plurality of non-cascading data packets from the source network device and to transmit a fourth data packet to the terminal device, where one non-cascading data packet includes one data unit, and the fourth data packet is obtained by cascading at least two data units of the plurality of non-cascading data packets.

[0257] In a possible implementation, the sequence number corresponding to the fourth data packet is within a sequence number value range, the sequence number value range includes at least one sequence number, and the sequence number value range is from a source network device.

[0258] The above is only an example. The processing unit 1401 and the communication unit 1402 may further perform other functions. For more detailed description, please refer to the relevant description in the method embodiment shown in Figure 6A to Figure 12B. Details will not be described again here.

[0259] FIG. 15 illustrates a communication device according to an embodiment of the present application. The communication device illustrated in FIG. 15 may be a hardware circuit implementation of the communication device illustrated in FIG. 14. The communication device is applicable to the above flow chart and performs the functions of the terminal device or the network device in the above method embodiment. For simplicity, FIG. 15 illustrates only the main components of the communication device.

[0260] 15, the communication device 1500 includes a processor 1510 and an interface circuit 1520. The processor 1510 and the interface circuit 1520 are coupled to each other. It may be understood that the interface circuit 1520 may be a transceiver or an input / output interface. Optionally, the communication device 1500 may further include a memory 1530 configured to store instructions to be executed by the processor 1510, to store input data required by the processor 1510 to execute the instructions, or to store data generated after the processor 1510 executes the instructions.

[0261] When the communications device 1500 is configured to perform the methods shown in Figures 6A to 12B, the processor 1510 is configured to perform the functions of the processing unit 1401 and the interface circuit 1520 is configured to perform the functions of the communications unit 1402.

[0262] When the communication device is a chip used in a terminal device, the chip in the terminal device implements the functions of the terminal device in the above method embodiment. The chip in the terminal device receives information from other modules (e.g., radio frequency modules or antennas) in the terminal device, where the information is transmitted by the network device to the terminal device. Alternatively, the chip in the terminal device transmits information to other modules (e.g., radio frequency modules or antennas) in the terminal device, where the information is transmitted by the terminal device to the network device.

[0263] When the communication device is a chip used in a network device, the chip in the network device performs the function of the network device in the above method embodiment. The chip in the network device receives information from other modules (e.g., radio frequency modules or antennas) in the network device, where the information is transmitted by the terminal device to the network device. Alternatively, the chip in the network device transmits information to other modules (e.g., radio frequency modules or antennas) in the network device, where the information is transmitted by the network device to the terminal device.

[0264] The processor in the embodiments of the present application may be a Central Processing Unit (CPU), or may be other general-purpose processors, Application-Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor, or may be any conventional processor.

[0265] In the embodiments of the present application, the processor may be a Random Access Memory (RAM), a Flash memory, a Read-Only Memory (ROM), a Programmable Read-Only Memory (PROM), an Erasable Programmable Read-Only Memory (EPROM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a register, a hard disk, a removable hard disk, a CD-ROM, or any other form of storage medium well known in the art. For example, the storage medium is coupled to the processor such that the processor can read information from the storage medium and write information to the storage medium. Indeed, the storage medium may be components of the processor. The processor and the storage medium may be located in an ASIC. Further, the ASIC may be located in a network device or a terminal device. Indeed, the processor and the storage medium may alternatively exist as discrete components in a network device or a terminal device.

[0266] It should be understood by those skilled in the art that the embodiments of the present application may be provided as a method, a system, or a computer program product. Thus, the present application may use the form of a hardware-only embodiment, a software-only embodiment, or an embodiment that combines software and hardware. In addition, the present application may use the form of a computer program product embodied in one or more computer usable storage media (including, but not limited to, disk memory, optical memory, etc.) that contain program code usable by a computer.

[0267] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the present application. It should be understood that computer program instructions can be used to implement each procedure and / or each block in the flowcharts and / or block diagrams, and combinations of procedures and / or blocks in the flowcharts and / or block diagrams. These computer program instructions can be provided for a processor of a general purpose computer, a special purpose computer, an embedded processor, or any other programmable data processing device, such that the instructions executed by the processor of the computer or any other programmable data processing device can cause a machine to generate an apparatus for implementing a particular function in one or more processes in the flowcharts and / or in one or more blocks in the block diagrams.

[0268] These computer program instructions may alternatively be stored in a computer-readable memory that can direct a computer or any other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable memory cause an artifact to be generated that includes an instruction apparatus that implements a particular function in one or more procedures in the flowcharts and / or in one or more blocks in the block diagrams.

[0269] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the scope of the present application. The present application is intended to cover such modifications and variations of the present application, provided that they fall within the scope of protection defined by the claims of the present application and their equivalent technologies.

Claims

1. A data transmission method applied to a source network device, comprising: performing a cascade connection process on at least two data units to obtain a first data packet, where data included in the at least two data units belong to the same radio bearer or quality of service flow of a terminal device, the first data packet being a Packet Data Convergence Protocol (PDCP) layer data packet in which the at least two data units share a PDCP header or a Service Data Adaptation Protocol (SDAP) layer data packet in which the at least two data units share a SDAP header, the PDCP header or the SDAP header including a field indicating the number of the at least two cascaded data units; Sending the first data packet to a target network device via a first tunnel; The method according to claim 1,

2. The method further includes transmitting first information to the target network device via the first tunnel; The first information indicates that the first data packet is a cascading data packet. The method of claim 1.

3. The method further includes transmitting a second data packet and second information to the target network device via the first tunnel; The second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device. The method of claim 2.

4. The method further includes transmitting a second data packet to the target network device via a second tunnel; the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device; The method of claim 1.

5. The method further comprises receiving address information for the second tunnel from the target network device. The method according to claim 4.

6. The method further comprises receiving address information for the first tunnel from the target network device. The method of claim 1.

7. The data size of the first data packet is X, and the maximum value of X is equal to or less than the smaller of a first maximum data volume and a second maximum data volume, or the maximum value of X is equal to or less than the smallest of a first maximum data volume, a second maximum data volume, and a third maximum data volume, and X is a number greater than 0; The first maximum data volume is a maximum data volume of a cascading data packet supported by the source network device, the second maximum data volume is a maximum data volume of a cascading data packet supported by the target network device, and the third maximum data volume is a maximum data volume of a cascading data packet supported by the terminal device.

7. The method according to any one of claims 1 to 6.

8. A data transmission method applied to a target network device, comprising: receiving a first data packet from a source network device via a first tunnel, the first data packet being a data packet obtained by cascading at least two data units, where data contained in the at least two data units belong to the same radio bearer or quality of service flow of a terminal device, the first data packet being a Packet Data Convergence Protocol (PDCP) layer data packet in which the at least two data units share a PDCP header or a Service Data Adaptation Protocol (SDAP) layer data packet in which the at least two data units share a SDAP header, where the PDCP header or the SDAP header includes a field indicating the number of the at least two cascaded data units; transmitting the first data packet to the terminal device; The method according to claim 1,

9. The method further includes receiving first information from the source network device via the first tunnel and transmitting the first information to the terminal device; The first information indicates that the first data packet is a cascading data packet. The method according to claim 8.

10. The method further includes receiving a second data packet and second information from the source network device via the first tunnel, and transmitting the second data packet and the second information by the target network device to the terminal device; The second information indicates that the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device.

10. The method of claim 9.

11. The method further includes receiving a second data packet from the source network device via a second tunnel and transmitting the second data packet to the terminal device; the second data packet is a non-cascading data packet, and the data in the second data packet and the data in the first data packet belong to the same radio bearer or quality of service flow of the terminal device; The method according to claim 8.

12. The data size of the first data packet is X, and the maximum value of X is equal to or less than the smaller of a first maximum data volume and a second maximum data volume, or the maximum value of X is equal to or less than the smallest of a first maximum data volume, a second maximum data volume, and a third maximum data volume, and X is a real number greater than 0; The first maximum data volume is a maximum data volume of a cascading data packet supported by the source network device, the second maximum data volume is a maximum data volume of a cascading data packet supported by the target network device, and the third maximum data volume is a maximum data volume of a cascading data packet supported by the terminal device. The method of claim 11.

13. In the first data packet, Y data units are cascaded, and a maximum value of Y is less than or equal to the smaller of a first maximum value and a second maximum value, or a maximum value of Y is less than or equal to the smallest of a first maximum value, a second maximum value, and a third maximum value, and Y is an integer greater than 1; The first maximum value is a maximum value supported by the source network device for the number of data units cascaded to obtain a cascading data packet, the second maximum value is a maximum value supported by the target network device for the number of data units cascaded to obtain a cascading data packet, and the third maximum value is a maximum value supported by the terminal device for the number of data units cascaded to obtain a cascading data packet.

13. A method according to any one of claims 8 to 12.

14. A communication device comprising a module adapted to carry out the method according to any one of claims 1 to 5.

15. A communication device comprising a module adapted to carry out the method according to any one of claims 8 to 11.

16. storing computer programs or instructions; The method according to any one of claims 1 to 5 and 8 to 11 is carried out when the computer program or the instructions are executed by a communication device. A computer-readable storage medium.

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