Method and apparatus for handover data transmission

Abstract

An embodiment of the present application provides a method and apparatus for data transmission during switching. A terminal device receives first indication information from a source network device, and the first indication information indicates whether to maintain the packet data convergence protocol PDCP replication function of the first radio bearer RB of the terminal device in the source network device when the terminal device switches from the source network device to the target network device. The terminal device transmits data of the first RB with the source network device according to the first indication information. By implementing this method, the reliability of data transmission during the switching process can be improved. At the same time, the terminal device can flexibly determine the data transmission mode of services with different reliability requirements during switching according to the indication of the source network device, thereby improving the flexibility of data transmission.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of wireless communications, and in particular to methods and devices for data transmission. Background Art

[0002] A significant feature of the fifth-generation (5G) mobile communication system compared to the fourth-generation (4G) mobile communication system is the added support for ultra-reliable and low-latency communications (URLLC) services. URLLC services include many types, and typical use cases include industrial control, unmanned driving, remote surgery, and smart grids. For URLLC services, a typical requirement is to achieve a reliability of 99.999% for sending 32 bytes of data within 1 millisecond (ms). It should be pointed out that the above performance indicators are only examples, and different URLLC services may have different reliability requirements. For example, in some extremely demanding industrial control application scenarios, the probability of successful transmission of URLLC service data needs to reach 99.9999999% within 0.25ms. Summary of the Invention

[0003] The present application provides a data transmission method and apparatus for improving the reliability of data transmission.

[0004] In the first aspect, the present application provides a method for data transmission, which is applied to the switching of a terminal device from a source network device to a target network device. The execution subject of the method is a terminal device or a module in the terminal device, and the terminal device is used as the execution subject for description. The terminal device receives first configuration information from the source network device, and the first configuration information is used to configure the packet data convergence protocol PDCP replication function of the first radio bearer RB of the terminal device in the source network device; the terminal device receives first indication information from the source network device, and the first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device when the terminal device switches from the source network device to the target network device; the terminal device transmits the data of the first RB with the source network device according to the first indication information. Wherein, before the switching is initiated, the terminal device performs dual-connection-based PDCP replication (also known as: DCduplication) transmission with the source network device and the target network device, that is, before the switching is initiated, the terminal device uses the RLC entity corresponding to the source network device and the RLC entity corresponding to the target network device, and uses the DC duplication function to transmit data with the source network device.

[0005] By implementing the method described in the first aspect, when the terminal device switches from the source network device to the target network device, the terminal device can determine whether to continue to maintain the PDCP replication function of the first RB in the source network device during the switch based on the first indication information of the source network device. For services with higher reliability requirements, for example, when the service carried by the first RB is a URLLC service, the source network device can indicate to continue to maintain the PDCP replication function of the first RB in the source network device during the switch, thereby ensuring that the terminal device can transmit the same data packet copied through the PDCP layer to the source network device through at least two RLC entities during the switch, thereby achieving 0 millisecond interruption of the PDCP replication function of the URLLC service during the switch process, thereby improving the reliability of the URLLC service during the switch process. For services with low reliability requirements, for example, when the service carried by the first RB is an eMBB service, the source network device can indicate not to maintain the PDCP replication function of the first RB in the source network device during the switch, that is, the PDCP replication function of the first RB in the source network device is released during the switch. By implementing the above method, the terminal device can flexibly determine the data transmission method of services with different reliability requirements during the switch based on the indication of the source network device, thereby improving the flexibility of data transmission.

[0006] In a possible implementation of the first aspect, the above-mentioned PDCP replication function of maintaining the first RB in the source network device specifically includes: maintaining a first radio link control RLC entity, wherein the first RLC entity is the RLC entity corresponding to the target network device before the handover is initiated. Maintaining the first RLC entity can also be understood as: the first RLC entity is not released, or it can also be understood as: the first RLC entity is in an available state, and the terminal device can transmit data with the source network device through the first RLC entity.

[0007] By implementing this method, the terminal device determines whether to continue to use the first RLC entity corresponding to the target network device before the handover is initiated to transmit the data of the first RB to the source network device based on the first indication information of the source network device. For services with higher reliability requirements, for example, when the service carried by the first RB is a URLLC service, the terminal device can continue to use the first RLC entity to transmit the data of the first RB to the source network device during the handover, thereby ensuring that the terminal device can transmit the same data packet copied through the PDCP layer to the source network device through at least two RLC entities (one is the first RLC entity, and the other is the RLC entity corresponding to the source network device), thereby improving the reliability of the URLLC service during the handover process.

[0008] In a possible implementation of the first aspect, when the first indication information indicates to maintain the PDCP replication function of the first RB in the source network device, the above-mentioned transmission of data of the first RB with the source network device according to the first indication information specifically includes: when the above-mentioned switching is initiated, submitting a data packet encrypted using the key of the source network device to the first RLC entity.

[0009] In a possible implementation of the first aspect, a terminal device receives second configuration information from a source network device, where the second configuration information is used to configure a PDCP duplication function of a first RB on a target network device, wherein the PDCP duplication function of the first RB on the target network device may be a carrier aggregation-based PDCP duplication (also known as CA duplication) function of the first RB on the target network device. When the above-mentioned handover is completed, the terminal device activates the PDCP duplication function of the first RB on the target network device.

[0010] By implementing this method, when the terminal device believes that the switching is completed, the terminal device can immediately activate the PDCP replication function of the first RB in the target network device, so that the terminal device can perform data transmission based on PDCP replication with the source network device before the switching is completed. After the switching is completed, the terminal device can immediately perform data transmission based on PDCP replication with the target network device, so that the data transmission based on PDCP replication between the terminal device and the network device is not interrupted due to the switching, thereby improving the reliability of data transmission.

[0011] In a possible implementation of the first aspect, a terminal device receives second configuration information from a source network device, where the second configuration information is used to configure a PDCP duplication function of a first RB on a target network device; and the terminal device receives second indication information from the target network device, where the second indication information is used to activate the PDCP duplication function of the first RB on the target network device. The PDCP duplication function of the first RB on the target network device may be a CAduplication function of the first RB on the target network device.

[0012] By implementing this method, the terminal device can activate the target network device according to the second indication information of the target network device to perform data transmission based on PDCP replication, thereby improving the flexibility of data transmission. At the same time, by indicating the activation method through the second indication information, the terminal device and the target network device have the same understanding of the activation time, thereby improving the reliability of data transmission.

[0013] In a possible implementation manner of the first aspect, the activating the PDCP duplication function of the first RB in the target network device specifically includes: activating an RLC entity associated with the first RB and corresponding to the target network device.

[0014] In a possible implementation of the first aspect, the first indication information further indicates that after the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device. Specifically, before the handover is completed, the first RLC entity is the RLC entity used for PDCP copy transmission between the terminal device and the source network device, and the source network device indicates through the first indication information that after the handover is completed, the first RLC entity is the RLC entity used for PDCP copy transmission between the terminal device and the target network device.

[0015] In a possible implementation of the first aspect, the terminal device receives third indication information from the source network device, where the third indication information indicates that after the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device. Specifically, before the handover is completed, the first RLC entity is the RLC entity used for PDCP duplicate transmission between the terminal device and the source network device, and the source network device indicates through the third indication information that after the handover is completed, the first RLC entity is the RLC entity used for PDCP duplicate transmission between the terminal device and the target network device.

[0016] In a possible implementation of the first aspect, the terminal device delivers a data packet encrypted using a key of the target network device to a second RLC entity, where the second RLC entity is one of the RLC entities associated with the first RB, and the second RLC entity is the RLC entity corresponding to the target network device after the handover is completed. The second RLC entity is different from the first RLC entity.

[0017] In a possible implementation of the first aspect, after the above-mentioned switching is completed, the terminal device submits a data packet encrypted using the key of the target network device to the first RLC entity.

[0018] By implementing this approach, the RLC entity corresponding to the target network device before the handover is initiated (the first RLC entity) is transformed into the RLC entity corresponding to the target network device after the handover is completed. This allows the terminal device to perform CA duplication-based data transmission with the target network device through the first RLC entity and the RLC entity corresponding to the target network device after the handover is completed (the second RLC entity), excluding the first RLC entity. This improves the reliability of data transmission. Furthermore, in this way, the target network device only needs to configure the second RLC entity, and the terminal device can perform CA duplication-based data transmission with the target network device after the handover is completed, thereby reducing resource configuration overhead.

[0019] In a possible implementation of the first aspect, after the above-mentioned switching is completed, the terminal device submits a data packet encrypted using the key of the source network device to the first RLC entity.

[0020] In a possible implementation of the first aspect, the terminal device delivers a data packet encrypted using a key of the target network device to a second RLC entity, where the second RLC entity is one of the RLC entities associated with the first RB, and the second RLC entity is the RLC entity corresponding to the target network device after the handover is completed. The second RLC entity is different from the first RLC entity.

[0021] In a possible implementation of the first aspect, when the terminal device receives a switching command from the source network device, it indicates that the switching is initiated; or, when the source network device receives a switching request confirmation message from the target network device, it indicates that the switching is initiated; or, when the source network device sends a switching request command to the target network device, it indicates that the switching is initiated.

[0022] In a possible implementation of the first aspect, after the terminal device initiates a random access process to the target network device, when it successfully accesses the target network device, it indicates that the handover is completed; or, when the terminal device sends an RRC reconfiguration message for ending the handover process to the target network device, it indicates that the handover is completed; or, when the target network device receives an RRC reconfiguration message for ending the handover process from the terminal device, it indicates that the handover is completed.

[0023] In the second aspect, the present application provides a method for data transmission, which is applied to the switching of a terminal device from a source network device to a target network device. The execution subject of the method is the source network device or a module in the source network device, and is described here by taking the source network device as the execution subject as an example. The source network device sends first configuration information to the terminal device, and the first configuration information is used to configure the packet data convergence protocol PDCP replication function of the first radio bearer RB of the terminal device in the source network device; the source network device sends first indication information to the terminal device, and the first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device when the terminal device switches from the source network device to the target network device; the source network device transmits the data of the first RB to the terminal device according to the first indication information.

[0024] By implementing the method described in the second aspect, when the terminal device switches from the source network device to the target network device, the source network device instructs the terminal device through the first indication information whether to continue to maintain the PDCP replication function of the first RB in the source network device during the switch. For services with higher reliability requirements, such as URLLC services, the source network device can indicate to continue to maintain the PDCP replication function of the first RB in the source network device during the switch, so as to ensure that the terminal device can transmit the same data packet copied through the PDCP layer with the source network device through at least two RLC entities, thereby achieving 0 millisecond interruption of the PDCP replication function of the URLLC service during the switch process, thereby improving the reliability of the URLLC service during the switch process. For services with low reliability requirements, such as when the service carried by the first RB is an eMBB service, the source network device can indicate not to maintain the PDCP replication function of the first RB in the source network device during the switch, that is, the PDCP replication function of the first RB in the source network device is released during the switch. By implementing the above method, the source network device can flexibly indicate the data transmission method of services with different reliability requirements during the switch, thereby improving the flexibility of data transmission.

[0025] In a possible implementation of the second aspect, the above-mentioned PDCP replication function of maintaining the first RB in the source network device specifically includes: maintaining the first radio link control RLC entity, wherein the first RLC entity is the RLC entity corresponding to the target network device before the handover is initiated.

[0026] In a possible implementation of the second aspect, when the first indication information indicates to maintain the PDCP replication function of the first RB in the source network device, the above-mentioned transmission of data of the first RB with the source network device according to the first indication information specifically includes: when the above-mentioned switching is initiated, receiving a data packet encrypted using the key of the source network device from the first RLC entity.

[0027] In a possible implementation manner of the second aspect, second configuration information is sent to the terminal device, where the second configuration information is used to configure a PDCP replication function of the first RB in the target network device.

[0028] In a possible implementation of the second aspect, the first indication information further indicates that after the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device. Specifically, before the handover is completed, the first RLC entity is the RLC entity used for PDCP copy transmission between the terminal device and the source network device, and the source network device indicates through the first indication information that after the handover is completed, the first RLC entity is the RLC entity used for PDCP copy transmission between the terminal device and the target network device.

[0029] In a possible implementation of the second aspect, the source network device sends third indication information to the terminal device, where the third indication information indicates that after the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device. Specifically, before the handover is completed, the first RLC entity is the RLC entity used for PDCP duplicate transmission between the terminal device and the source network device, and the source network device indicates through the third indication information that after the handover is completed, the first RLC entity is the RLC entity used for PDCP duplicate transmission between the terminal device and the target network device.

[0030] In a possible implementation of the second aspect, after the above-mentioned handover is completed, the source network device receives a data packet encrypted using the key of the source network device from the first RLC entity; and the source network device forwards the data packet encrypted using the key of the source network device to the target network device. Correspondingly, after the above-mentioned handover is completed, the target network device receives a data packet forwarded by the source network device and encrypted using the key of the source network. In a possible design, the target network device receives a data packet encrypted using the key of the target network device from a second RLC entity, the second RLC entity being one of the RLC entities associated with the first RB, the second RLC entity being the RLC entity corresponding to the target network device after the handover is completed. The second RLC entity is different from the first RLC entity.

[0031] By implementing this method, after the above-mentioned handover is completed, the terminal device can transmit the same data with the target network device through the first RLC entity and the second RLC entity. For example, the terminal device sends a copy of the data to the target network device through the second RLC entity, and the terminal device sends another copy of the same data to the source network device through the first RLC entity. When the source network device receives the data from the terminal device through the first RLC entity, it forwards the data to the target network device. As a result, after the handover is completed, the terminal device can transmit data with the target network device through at least two RLC entities (commonly known as "two legs"), thereby improving the reliability of data transmission.

[0032] In a possible implementation of the second aspect, when the terminal device receives a switching command from the source network device, it indicates that the switching is initiated; or, when the source network device receives a switching request confirmation message from the target network device, it indicates that the switching is initiated; or, when the source network device sends a switching request command to the target network device, it indicates that the switching is initiated.

[0033] In a possible implementation of the second aspect, after the terminal device initiates a random access process to the target network device, when it successfully accesses the target network device, it indicates that the switching is completed; or, when the terminal device sends an RRC reconfiguration message for ending the switching process to the target network device, it indicates that the switching is completed; or, when the target network device receives an RRC reconfiguration message for ending the switching process from the terminal device, it indicates that the switching is completed.

[0034] According to a third aspect, a communication device is provided, comprising a functional module for implementing the method of the aforementioned first aspect or any possible implementation manner of the first aspect.

[0035] In a fourth aspect, a communication device is provided, comprising a functional module for implementing the method in the aforementioned second aspect and any possible implementation manner of the second aspect.

[0036] In a fifth aspect, a communication device is provided, comprising a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method in the aforementioned first aspect or any possible implementation of the first aspect through a logic circuit or executing code instructions.

[0037] In the sixth aspect, a communication device is provided, comprising a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method in the aforementioned second aspect or any possible implementation of the second aspect through a logic circuit or executing code instructions.

[0038] In the seventh aspect, a computer-readable storage medium is provided, which stores a computer program or instruction. When the computer program or instruction is executed, the method in the aforementioned first aspect or any possible implementation of the first aspect is implemented.

[0039] In an eighth aspect, a computer-readable storage medium is provided, in which a computer program or instruction is stored. When the computer program or instruction is executed, the method in the aforementioned second aspect or any possible implementation of the second aspect is implemented.

[0040] In a ninth aspect, a computer program product comprising instructions is provided, which, when executed, implements the method in the aforementioned first aspect or any possible implementation manner of the first aspect.

[0041] In a tenth aspect, a computer program product comprising instructions is provided, which, when executed, implements the method in the aforementioned second aspect or any possible implementation manner of the second aspect.

[0042] In the eleventh aspect, a computer program is provided, which includes codes or instructions. When the codes or instructions are executed, the method in the first aspect or any possible implementation of the first aspect is implemented.

[0043] In a twelfth aspect, a computer program is provided, which includes codes or instructions. When the codes or instructions are executed, the method in the aforementioned second aspect or any possible implementation of the second aspect is implemented.

[0044] In a thirteenth aspect, a chip system is provided, comprising a processor and a memory, for implementing at least one of the methods described in the first and second aspects. The chip system may consist of a chip alone, or may include a chip and other discrete components.

[0045] In a fourteenth aspect, a communication system is provided, the system comprising the apparatus described in the third aspect or the fifth aspect (such as a terminal device), and the apparatus described in the fourth aspect or the sixth aspect (such as a source network device). BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of the architecture of a communication system used in an embodiment of the present application;

[0047] Figure 2 A schematic diagram of a CU and DU separation architecture applied in an embodiment of the present application;

[0048] Figure 3 This is a schematic diagram of an architecture for implementing the PDCP duplication function in a DC scenario provided by an embodiment of the present application;

[0049] Figure 4 This is a schematic diagram of an architecture for implementing the PDCP duplication function in a CA scenario provided by an embodiment of the present application;

[0050] Figure 5 A schematic diagram of a switching process provided in an embodiment of the present application;

[0051] Figure 6 A flowchart of a data transmission method provided in an embodiment of the present application;

[0052] Figure 7 A schematic diagram of implementing the PDCP duplication function provided in an embodiment of the present application;

[0053] Figure 8 A schematic diagram of the structure of a first message provided in an embodiment of the present application;

[0054] Figure 9 and Figure 10 A schematic diagram of implementing the PDCP duplication function provided in an embodiment of the present application;

[0055] Figure 11 and Figure 12 A schematic diagram of the structure of a possible communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The technical solutions provided in the embodiments of the present application can be applied to various communication systems, such as long-term evolution (LTE) systems, fifth-generation (5G) mobile communication systems, WiFi systems, future communication systems, or systems integrating multiple communication systems, etc., without limitation in the embodiments of the present application. 5G can also be referred to as new radio (NR).

[0057] The technical solutions provided in the embodiments of the present application can be applied to various communication scenarios, for example, one or more of the following communication scenarios: enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), machine type communication (MTC), massive machine type communication (mMTC), device-to-device (D2D), vehicle to everything (V2X), vehicle to vehicle (V2V), and Internet of Things (IoT), etc.

[0058] The technical solution provided in the embodiment of the present application can be applied to communication between communication devices. Communication between communication devices may include: communication between network devices and terminal devices, communication between network devices and network devices, and / or communication between terminal devices and terminal devices. In the embodiment of the present application, the term "communication" can also be described as "transmission", "information transmission", or "signal transmission", etc. Transmission may include sending and / or receiving. In the embodiment of the present application, the technical solution is described using the communication between network devices and terminal devices as an example. Those skilled in the art may also use the technical solution for communication between other scheduling entities and subordinate entities, such as communication between a macro base station and a micro base station, such as communication between a first terminal device and a second terminal device. Among them, the scheduling entity can allocate air interface resources to the subordinate entity. Air interface resources include one or more of the following resources: time domain resources, frequency domain resources, code resources, and space resources. In the embodiment of the present application, multiple can be two, three, four or more, and the embodiment of the present application is not limited.

[0059] In an embodiment of the present application, the communication between the network device and the terminal device includes: the network device sending a downlink signal / information to the terminal device, and / or the terminal device sending an uplink signal / information to the network device.

[0060] In the embodiments of this application, " / " can indicate that the objects associated with each other are in an "or" relationship. For example, A / B can mean A or B. "And / or" can be used to describe the existence of three relationships between the associated objects. For example, A and / or B can mean: A exists alone, A and B exists simultaneously, and B exists alone. A and B can be singular or plural. In the embodiments of this application, words such as "first" and "second" can be used to distinguish between technical features with the same or similar functions. The words "first" and "second" do not limit the quantity or execution order, and the words "first" and "second" do not necessarily mean different. In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. An embodiment or design described as "exemplary" or "for example" should not be construed as being preferred or advantageous over other embodiments or design solutions. The use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete way to facilitate understanding.

[0061] Figure 1 Schematic diagram of the architecture of a communication system to which the embodiments of the present application can be applied. Figure 1 As shown, the communication system includes a terminal device 110 and two network devices (such as Figure 1 Network device 120 and network device 130 in). Figure 1 This is just a schematic diagram, and the embodiments of the present application do not limit the number of network devices and terminal devices included in the communication system.

[0062] The terminal devices involved in the embodiments of the present application may also be referred to as terminals, user equipment (UE), mobile stations, mobile terminals, etc. The terminal devices may be mobile phones, tablet computers, computers with wireless transceiver functions, virtual reality terminal devices, augmented reality terminal devices, wireless terminals in industrial control, wireless terminals in unmanned driving, wireless terminals in remote surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, etc. The embodiments of the present application do not limit the specific technologies and specific device forms adopted by the terminal devices. In the embodiments of the present application, the device for realizing the functions of the terminal device may be a terminal device; it may also be a device that can support the terminal device to realize the function, such as a chip system, which can be installed in the terminal device or used in combination with the terminal device. In the embodiments of the present application, the chip system may be composed of chips, or may include chips and other discrete devices. In the technical solutions provided in the embodiments of the present application, the technical solutions provided in the embodiments of the present application are described by taking the device for realizing the functions of the terminal device as an example.

[0063] The network device involved in the embodiments of the present application is an access network (radio access network, RAN) device in the mobile communication system that the terminal device accesses by wireless means, and may include but is not limited to: a base station, an evolved base station (evolvedNodeB, eNodeB), a transmission reception point (TRP), a next generation base station (next generation NodeB, gNB) in a 5G mobile communication system, a base station in a future mobile communication system, or an access node in a WiFi system. The interface between network devices is called an Xn interface, and the interface between a network device and a terminal device may be a Uu interface (or air interface). Of course, in future communications, the names of these interfaces may remain unchanged, or may be replaced by other names, and this application does not limit this.

[0064] The communication between network equipment and terminal equipment follows a certain protocol layer structure. For example, the control plane protocol layer structure may include the functions of protocol layers such as the RRC layer, packet data convergence protocol (PDCP) layer, radio link control (RLC) layer, media access control (MAC) layer and physical layer; the user plane protocol layer structure may include the functions of protocol layers such as the PDCP layer, RLC layer, MAC layer and physical layer. In one possible implementation, a service data adaptation protocol (SDAP) layer may also be included above the PDCP layer.

[0065] The network equipment may include a centralized unit (CU) and a distributed unit (DU). The interface between the CU and the DU may be referred to as an F1 interface. Figure 2 As shown. Among them, the control plane (CP) interface can be F1-C, and the user plane (UP) interface can be F1-U. CU and DU can be divided according to the protocol layer of the wireless network, for example, the functions of the PDCP layer and above protocol layers are set in the CU, and the functions of the protocol layers below the PDCP layer (such as the RLC layer and the MAC layer, etc.) are set in the DU. The signaling generated by the CU can be sent to the terminal device through the DU, or the signaling generated by the terminal device can be sent to the CU through the DU. The DU can directly encapsulate the signaling through the protocol layer and transparently transmit it to the terminal device or CU without parsing it. The embodiments of the present application do not limit the specific technology and specific device form adopted by the network device. In the embodiments of the present application, the device for realizing the function of the network device can be a network device; it can also be a device that can support the network device to realize the function, such as a chip system, which can be installed in the network device or used in combination with the network device. In the embodiments of the present application, the technical solution provided by the embodiments of the present application is described by taking the device for realizing the function of the network device as an example that the network device is used.

[0066] Network equipment and terminal equipment can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; can be deployed on the water surface; or, can be deployed in the air on aircraft, balloons or artificial satellites. The embodiments of the present application do not limit the application scenarios of network equipment and terminal equipment. Network equipment and terminal equipment can communicate through authorized spectrum, can communicate through unauthorized spectrum, or can communicate through authorized spectrum and unauthorized spectrum. Network equipment and terminal equipment can communicate through spectrum below 6 gigahertz (GHz), can communicate through spectrum above 6 GHz, or can use spectrum below 6 GHz and spectrum above 6 GHz. The embodiments of the present application do not limit the spectrum resources used between network equipment and terminal equipment.

[0067] Some of the terms used in the embodiments of the present application are explained below to facilitate understanding by those skilled in the art.

[0068] (1) Radio bearer (RB)

[0069] Data is transmitted between terminal devices and network devices by establishing at least one radio bearer (RB). Radio bearers can be divided into signaling radio bearers (SRB) for transmitting signaling data and data radio bearers (DRB) for transmitting service data. A set of functional entities for the same radio bearer includes a PDCP entity, at least one radio link control RLC entity corresponding to the PDCP entity, and at least one MAC entity corresponding to at least one RLC entity. The PDCP entity is located in the PDCP layer, the RLC entity is located in the RLC layer, and the MAC entity is located in the MAC layer.

[0070] Taking downlink data transmission as an example, after a network device's SDAP layer entity receives data from an upper layer, it can map the data to the PDCP layer entity for the corresponding RB based on the data's Quality of Service (QoS) flow indicator (QFI). The PDCP layer entity can then transmit the data to at least one RLC layer entity corresponding to the PDCP layer entity. The at least one RLC layer entity then transmits the data to the corresponding MAC layer entity. The MAC layer entity then generates a transport block, which is then wirelessly transmitted via the corresponding physical layer entity. Data is encapsulated within each layer. Data received by a layer from the upper layer is considered a service data unit (SDU) for that layer. After layer encapsulation, it becomes a protocol data unit (PDU) and is then passed to the next layer. For example, data received by a PDCP layer entity from an upper layer is called a PDCP SDU, and data sent by a PDCP layer entity to a lower layer is called a PDCP PDU. Data received by an RLC layer entity from an upper layer is called an RLC SDU, and data sent by an RLC layer entity to a lower layer is called an RLC PDU. Among them, data can be transmitted between different layers through corresponding channels. For example, data can be transmitted between the RLC layer entity and the MAC layer entity through a logical channel (LCH), and data can be transmitted between the MAC layer entity and the physical layer entity through a transport channel.

[0071] (2) Dual Connectivity (DC)

[0072] DC refers to a terminal device being connected to two network devices simultaneously. The two network devices connected to the terminal device can be base stations using the same radio access technology, such as both base stations in the LTE communication system or both base stations in the 5G mobile communication system. Alternatively, the two base stations connected to the terminal device can be base stations using different radio access technologies, such as one base station in the LTE communication system and the other in the 5G mobile communication system.

[0073] (3) Carrier aggregation (CA)

[0074] CA refers to aggregating multiple component carriers (CCs) to provide services for a terminal device to achieve a larger transmission bandwidth, thereby improving uplink and downlink transmission rates.

[0075] (4) PDCP duplication

[0076] PDCP duplication refers to duplicating a radio bearer's data packet into multiple identical packets (i.e., duplicate packets) at the PDCP layer. These duplicate packets are then delivered to multiple different RLC entities for transmission. For example, each RLC entity transmits the data packet to the MAC layer via the logical channel corresponding to that RLC entity. Generally speaking, PDCP duplication differs from retransmission, which refers to the retransmission of the same data packet after a transmission failure. PDCP duplication, on the other hand, involves duplicating a single data packet into multiple packets, each of which is transmitted via multiple RLC entities.

[0077] In the embodiment of the present application, PDCP duplication includes PDCP duplication for DC scenario (also referred to as DC duplication) and PDCP duplication for CA scenario (also referred to as CA duplication). The following describes how to implement the PDCP duplication function for DC scenario and CA scenario respectively.

[0078] (1)DC duplication

[0079] Figure 3 The present invention shows a network architecture for implementing the DC duplication function in a DC scenario. For network devices, the DC scenario involves a primary network device and a secondary network device. For one RB, there is one PDCP entity, one RLC entity, and one MAC entity in the primary network device, and one RLC entity and one MAC entity in the secondary network device. For this RB, there is one PDCP entity, two RLC entities, and two MAC entities in the terminal device. For one RB, the primary network device can also have an SDAP entity above the PDCP entity, and the terminal device can also have an SDAP entity above the PDCP entity.

[0080] In the DC scenario, a terminal device is simultaneously connected to two network devices, namely the primary network device and the secondary network device. If the DC duplication function is configured for a certain RB, the two identical data packets belonging to the RB that are duplicated by the PDCP layer will be transmitted to two different RLC entities, and respectively transmitted to two different MAC entities through different logical channels, ultimately forming two MAC PDUs that are transmitted on the cell resources scheduled by the two different MAC entities. For the network device, the PDCP layer in the primary network device will transmit the two duplicated data packets to two different RLC entities, which are located in the primary network device and the secondary network device, respectively. Afterwards, the RLC entity in the primary network device will transmit the received data packets to the MAC entity in the primary network device, and the RLC entity in the secondary network device will transmit the received data packets to the MAC entity in the secondary network device. The two MAC entities will transmit the data packets through their respective cell resources. For the terminal device, the two RLC entities and the two MAC entities are both located in the terminal device. For example, in a DC scenario, there can be two cell groups providing services for terminal devices, namely the master cell group (MCG) and the secondary cell group (SCG), where the master cell group is managed and configured by the main network device, and the secondary cell group is managed and configured by the main network device or the secondary network device.

[0081] Optionally, the network device may further configure one of the two RLC entities as a primary RLC entity (also commonly known as a primary leg) and the other RLC entity as a secondary RLC entity (also commonly known as a secondary leg) for the terminal device, for example, the network device may configure Figure 3 In the example, RLC1 is the primary RLC entity, and RLC2 is the secondary RLC entity. In the embodiment of the present application, since there is a one-to-one correspondence between RLC entities and logical channels, the primary leg can refer to the primary RLC entity or the logical channel associated with the primary RLC entity, also known as the primary logical channel; the secondary leg can refer to the secondary RLC entity or the logical channel associated with the secondary RLC entity, also known as the secondary logical channel.

[0082] When a network device configures the DC duplication function for a radio bearer through radio resource control (RRC) signaling, it can indicate whether the initial state of the DC duplication function of the radio bearer is activated or deactivated. Optionally, the network device can also configure the activation / deactivation of the DC duplication function of the radio bearer through a MAC control element (MACCE).

[0083] When the DC duplication function is activated, the terminal device can receive the same data packet from the primary network device through the primary RLC entity and the secondary RLC entity, which is copied through the PDCP layer of the primary network device. Alternatively, the terminal device can copy the data packet into two copies at the PDCP layer of the terminal device and send them to the primary network device and the secondary network device through the primary RLC entity and the secondary RLC entity respectively. When the terminal device transmits PDCP control PDUs with the network device, the terminal device can only transmit PDCP control PDUs with the network device through the primary RLC entity.

[0084] When the DC duplication function is deactivated, it falls back to the split bearer, that is, the terminal device can transmit different data packets to the primary network device and the secondary network device respectively through the primary RLC entity and the secondary RLC entity on the terminal device side. For example, when the amount of data to be transmitted between the terminal device and the network device exceeds the threshold value, the terminal device transmits different data packets to the primary network device and the secondary network device respectively through the primary RLC entity and the secondary RLC entity; when the above data amount does not exceed the threshold value, the terminal device only transmits data packets to the primary network device through the primary RLC entity, wherein the above threshold value is configured by the network device through the RRC message.

[0085] (2)CA duplication

[0086] Figure 4A network architecture for implementing the PDCP duplication function in a CA scenario is shown. In the CA scenario, a terminal device is connected to a network device, and at least two carriers (or cells) serve the terminal device under the same network device. For one RB, there is one PDCP entity, two RLC entities and one MAC entity in the network device. There is one PDCP entity, two RLC entities and one MAC entity in the terminal device. When the network device configures the PDCP duplication function for a radio bearer, two identical data packets that have been replicated at the PDCP layer will be transmitted to two different RLC entities, and these two RLC entities will transmit them to the same MAC entity through different logical channels. At this time, since the two identical data packets are transmitted to the same MAC entity, the MAC entity will put the two data packets into one MAC PDU for transmission. Therefore, in order to allow the two data packets to be transmitted separately through two cells, a parameter can be configured for the logical channel, such as parameter A. The value of parameter A is used to indicate different cells, thereby ensuring that the two identical data packets can eventually form two MAC PDUs for transmission on different cells, thereby improving reliability.

[0087] Currently, CA duplication can support a data packet of a radio bearer to be duplicated into two copies at the PDCP layer and transmitted through two RLC entities. Optionally, the network device can also configure one RLC entity as the primary RLC entity and the other RLC entity as the secondary RLC entity, such as Figure 4 RLC1 is the primary RLC entity and RLC2 is the secondary RLC entity. When the network device configures the PDCP duplication function for a radio bearer through RRC signaling, it can indicate whether the initial state of the PDCP duplication function of the radio bearer is activated or deactivated. Optionally, the network device can also configure the activation / deactivation of the PDCP duplication function of the radio bearer through MAC CE. When the CAduplication function is activated, the terminal device can transmit data with the network device through the primary RLC entity and the secondary RLC entity; when the CAduplication function is deactivated, the terminal device can only transmit data with the network device through the primary RLC entity.

[0088] (V) Switching process

[0089] Before the terminal device switches from one network device to another, the network device that provides services for at least one RB of the terminal device can be called a source network device; after the switch, the network device that provides services for at least one RB of the terminal device can be called a target network device. Figure 5A schematic diagram of a switching process, including:

[0090] S501, the source network device sends a radio resource control RRC reconfiguration message to a terminal device in an RRC connected state. The RRC reconfiguration message includes parameters such as a measurement object, a measurement configuration, and a measurement identifier.

[0091] S502, after measuring the measurement object according to the RRC reconfiguration message, the terminal device reports the measurement result to the source network device. For example, the terminal device reports that the signal strength of the current serving cell is lower than the threshold value and the signal strength of the target cell is higher than the threshold value.

[0092] S503: After receiving the measurement report in S502, the source network device decides whether to perform a handover. If a handover is required, the source network device sends a handover request message to the target network device.

[0093] S504: If the target network device allows the terminal device to access, the target network device sends a handover request acknowledgement message to the source network device. The handover request acknowledgement message may include an RRC reconfiguration message generated by the target network device for the terminal device, and the RRC reconfiguration message includes the configuration required for the terminal device to access the target network device.

[0094] S505. The source network device sends a handover command to the terminal device, where the handover command includes an RRC reconfiguration message.

[0095] S506, the terminal device performs switching according to the switching command in S505: the terminal device disconnects from the source network device and accesses the target network device through a random access process.

[0096] S507: When the terminal device successfully accesses the target network device, the handover is completed. The terminal device ends the handover process by sending an RRC reconfiguration completion message to the target network device.

[0097] In the above switching process, a possible implementation method is that after the terminal device receives the switching command from the source network device (ie Figure 5 S505 in the above), and before successfully accessing the target network device (i.e. Figure 5 In S507 in the figure), the connection with the source network device can be kept unchanged, that is, the terminal device can continue to communicate with the source network device through the RLC entity (denoted as RLCA) associated with the source network device. In the embodiment of the present application, this switching method is called dual active protocol stack (DAPS) switching.

[0098] Exemplarily, in the DAPS switching process, after the terminal device receives the switching command from the source network device, the terminal device will establish an RLC entity corresponding to the target network device (denoted as RLC B). After receiving the switching command and before successfully accessing the target network device, the terminal device transmits data with the source network device through RLC A. At this time, RLC B is in a deactivated state, that is, the terminal device does not transmit data with the target network device through RLC B. After the terminal device successfully accesses the target network device, the terminal device no longer transmits data with the source network device through RLC A, but transmits data with the source network device through RLC B. Through the DAPS switching method, the data transmission between the terminal device and the network device can be ensured not to be interrupted during the process of switching from one network device to another, thereby reducing the delay of data transmission.

[0099] However, although the existing DAPS switching process can ensure that data transmission between the terminal device and the network device is not interrupted, the terminal device can only transmit data with the source network device or the target network device through one RLC entity, which cannot meet the high reliability requirements of the URLLC service. Based on the above problems, the embodiments of this application will mainly study how to improve the reliability of data transmission in the scenario where the terminal device is switched.

[0100] Figure 6 This is a flow chart of a data transmission method provided by an embodiment of the present application. This embodiment involves the specific process of data transmission between the terminal device and the source network device and the target network device during the process of the terminal device switching from the source network device to the target network device. Figure 6 In the embodiment shown, before the terminal device initiates the handover, the terminal device performs DC duplication-based transmission with the source network device and the target network device, wherein the source network device is the primary network device of the terminal device before the handover is initiated, and the target network device is the secondary network device of the terminal device before the handover is initiated. Figure 6 As shown, the method may include: S601 to S607, wherein S607 is an optional operation. The embodiment of the present application does not limit the execution order of S601 to S607.

[0101] S601: A source network device sends first configuration information to a terminal device. Correspondingly, the terminal device receives the first configuration information from the source network device. Optionally, the first configuration information may be carried in an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message.

[0102] The first configuration information is used to configure the PDCP duplication function of the first RB of the terminal device in the source network device. In an embodiment of the present application, the first configuration information configures the PDCP duplication function of the first RB of the terminal device in the source network device, which can be understood as: the terminal device is connected to the source network device and the target network device at the same time, and the terminal device can use the DC duplication function to transmit data of the first RB with the source network device and the target network device, wherein the source network device is the primary network device connected to the terminal device, and the target network device is the secondary network device connected to the terminal device.

[0103] Exemplarily, the first configuration information includes one or more of the following parameters:

[0104] 1. Identification of the first RB.

[0105] 2. The identifier of the primary RLC entity associated with the first RB. The first RB is associated with a primary RLC entity, which cannot be dynamically deactivated. Optionally, the terminal device can transmit PDCP control PDUs to the network device via the primary RLC entity.

[0106] 3. The identifier of the secondary RLC entity associated with the first RB. The first RB can be associated with one or more secondary RLC entities, and the secondary RLC entity can be dynamically deactivated. Optionally, the terminal device cannot transmit PDCP control PDUs through the secondary RLC entity, but can transmit PDCP data PDUs replicated by the PDCP layer through the secondary RLC entity.

[0107] 4. DAPS configuration information, used to indicate whether the first RB supports DAPS switching operations.

[0108] After receiving the first configuration information, the terminal device establishes a PDCP entity associated with the first RB on the terminal device side (hereinafter referred to as the first PDCP entity). Optionally, the first PDCP entity may establish an encryption function applicable to the source network device, that is, the first PDCP entity uses a key applicable to the source station (hereinafter referred to as the first key) to encrypt and decrypt data packets received by the first PDCP entity.

[0109] Optionally, the first PDCP entity may establish an integrity protection function applicable to the source network device, that is, the first PDCP entity uses the integrity protection algorithm and integrity protection key applicable to the source station to perform integrity protection and integrity verification on the data packets received by the first PDCP entity. In an embodiment of the present application, integrity protection means that the sending end uses the integrity protection algorithm to calculate the message authentication code for integrity (MAC-I) of the data to be sent, and the sending end sends the MAC-I and the above-mentioned data to be sent to the receiving end. The receiving end calculates the expected MAC-I according to the same integrity protection algorithm and compares the expected MAC-I with the received MAC-I. If the two are the same, the receiving end believes that the content of the data has not been tampered with. If they are not the same, the receiving end believes that the data has been tampered with.

[0110] Optionally, the first PDCP entity may also establish a header compression function applicable to the source network device. In an embodiment of the present application, the header compression function means that the sending end can compress the sub-headers of the transport layer, network layer, etc. of the data to be sent based on the robust header compression (ROHC) architecture and / or the ethernet header compression (EHC) architecture. Exemplarily, the sending end establishes a compression context (context) and indicates the content of the uncompressed sub-header through the context, thereby reducing the overhead of the sub-header. Correspondingly, the receiving end can restore the content of the uncompressed sub-header through the context.

[0111] After the terminal device receives the first configuration information, the terminal device can also establish an RLC entity associated with the first RB (also referred to as the RLC entity associated with the first PDCP). Exemplarily, the first RB is associated with two RLC entities, namely RLC1 and RLC2. Among them, RLC1 is the RLC entity corresponding to the source network device, and RLC2 is the RLC entity corresponding to the target network device. The terminal device can transmit data with the source network device through RLC1 and / or RLC2. Exemplarily, the PDCP entity of the terminal device uses the first key to encrypt the PDCP data PDU, and submits the encrypted PDCP data PDU to RLC1 and / or RLC2, and then RLC1 and / or RLC2 transmits the data to the corresponding MAC entity, and the MAC layer entity generates a transmission block, which is then transmitted to the source network device through the air interface by the corresponding physical layer entity.

[0112] If RLC1 is the main RLC entity and the initial state of RLC2 is deactivated, the terminal device transmits data with the network device through RLC1; if RLC1 is the main RLC entity and the initial state of RLC2 is activated, the terminal device transmits data with the network device through RLC1 and RLC2; if RLC2 is the main RLC entity and the initial state of RLC1 is deactivated, the terminal device transmits data with the network device through RLC2; if RLC2 is the main RLC entity and the initial state of RLC1 is activated, the terminal device transmits data with the network device through RLC1 and RLC2.

[0113] Optionally, the source network device further sends a first message to the terminal device, and correspondingly, the terminal device receives the first message from the network device. The first message is used to activate or deactivate the secondary RLC entity associated with the first RB. Optionally, the first message is a MAC CE. For example, a possible form of the first message is as follows: Figure 8 As shown, DRB ID is the identifier of DRB, RLCi is the RLC entity associated with the DRB (i is a non-negative integer), if RLCi=1, it means activating the PDCP duplication function of RLCi; if RLCi=0, it means deactivating the PDCP duplication function of RLCi.

[0114] The source network device may also send third configuration information to the terminal device, and correspondingly, the terminal device receives the third configuration information from the source network device. The third configuration information is used to configure the primary cell group associated with the source network device, and / or the secondary cell group associated with the target network device. Among them, the primary cell group includes a primary cell and at least one secondary cell, the primary cell group is associated with a MAC entity, and the MAC entity is associated with at least one RLC entity; the secondary cell group includes a primary cell and at least one secondary cell, the secondary cell group is associated with a MAC entity, and the MAC entity is associated with at least one RLC entity. Optionally, the third configuration information may be carried on an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message. Optionally, the third configuration information and the above-mentioned first configuration information may be carried on the same or different messages. Optionally, the third configuration information and the first configuration information may be sent simultaneously or separately, and the embodiment of the present application does not limit the order in which the third configuration information and the first configuration information are sent.

[0115] S602: The source network device sends first indication information to the terminal device. Correspondingly, the terminal device receives the first indication information from the source network device. The first indication information may be carried in an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message. Optionally, the first indication information and the first configuration information may be carried in the same or different messages.

[0116] The first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device when the terminal device switches from the source network device to the target network device.

[0117] Specifically, the first indication information indicates whether the terminal device maintains the PDCP replication function of the first RB in the source network device during the period from the start of the above-mentioned handover to the completion of the above-mentioned handover. The manner in which the first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device includes but is not limited to the following manners:

[0118] Method 1

[0119] If the value of the first indication information is a first value, the terminal device maintains the PDCP replication function of the first RB on the source network device; if the value of the first indication information is a second value, the terminal device does not maintain the PDCP replication function of the first RB on the source network device. Exemplarily, the first value can be "true" or "enabled"; the second value can be "false", "disabled", or the second value can be empty.

[0120] Method 2

[0121] When the source network device sends the first indication information to the terminal device, that is, when the terminal device receives the first indication information from the source network device, the first indication information instructs the terminal device to maintain the PDCP copy function of the first RB in the source network device; when the source network device does not send the first indication information to the terminal device, that is, when the terminal device does not receive the first indication information from the source network device, the first indication information instructs the terminal device not to maintain the PDCP copy function of the first RB in the source network device; or, when the source network device sends the first indication information to the terminal device, that is, when the terminal device receives the first indication information from the source network device, the first indication information instructs the terminal device not to maintain the PDCP copy function of the first RB in the source network device; when the source network device does not send the first indication information to the terminal device, that is, when the terminal device does not receive the first indication information from the source network device, the first indication information instructs the terminal device to maintain the PDCP copy function of the first RB in the source network device. Optionally, in method 2, the value of the first indication information can be "true" or "false".

[0122] In the above-mentioned Mode 1 and Mode 2, the terminal device maintains the PDCP duplication function of the first RB on the source network device, which can be understood as: the terminal device maintains the use of the DC duplication function to transmit data of the first RB with the source network device and the target network device. The terminal device does not maintain the PDCP duplication function of the first RB on the source network device, which can be understood as: the terminal device releases the PDCP duplication function of the first RB on the source network device, that is, the terminal device no longer uses the DC duplication function to transmit data of the first RB with the source network device and the target network device.

[0123] In an embodiment of the present application, the sign of switching initiation may include: the terminal device receives a switching command from the source network device; or, the sign of switching initiation may include: the source network device receives a switching request confirmation message from the target network device; or, the sign of switching initiation may include: the source network device sends a switching request command to the target network device. This embodiment of the present application does not limit this.

[0124] In an embodiment of the present application, the sign of the completion of the handover may include: the terminal device successfully accesses the target network device after initiating a random access process to the target network device, or the sign of the completion of the handover may include: the terminal device sends an RRC reconfiguration message to the target network device to end the handover process; or the sign of the completion of the handover may include: the target network device receives an RRC reconfiguration message from the terminal device to end the handover process. The embodiment of the present application does not limit this.

[0125] S603: The source network device sends a switching request message to the target network device. Correspondingly, the target network device receives the switching request message from the source network device.

[0126] S604: If the target network device allows the terminal device to access, the target network device sends a handover request confirmation message to the source network device.

[0127] S605: The source network device sends a handover command to the terminal device, where the handover command includes an RRC reconfiguration message. After the terminal device receives the handover command from the source network device, it starts a handover process.

[0128] S606. The terminal device transmits data of the first RB to the source network device according to the first indication information.

[0129] Specifically, the above-mentioned maintaining the PDCP replication function of the first RB on the source network device includes: maintaining a first radio link control RLC entity, wherein the first RLC entity is the RLC entity corresponding to the target network device before the handover is initiated. The above-mentioned not maintaining the PDCP replication function of the first RB between the source network device and the target network device includes: the first radio link control RLC entity is released, wherein the first RLC entity is the RLC entity corresponding to the target network device.

[0130] In the embodiment of the present application, maintaining the first RLC entity can also be understood as: the first RLC entity is not released, or can also be understood as: the first RLC entity is in an available state, and the terminal device can transmit data with the source network device through the first RLC entity. When the first indication information indicates to maintain the PDCP replication function of the first RB in the source network device, the terminal device can transmit data with the source network device through the first RLC entity after the above-mentioned handover is initiated. For example, after the above-mentioned handover is initiated, the terminal device can submit a data packet encrypted using the first key to the first RLC entity.

[0131] In the embodiment of the present application, the first RLC entity is released, which can also be understood as: the first RLC entity is suspended, or can also be understood as: the first RLC entity is in an unavailable state, and the terminal device cannot transmit data with the source network device through the first RLC entity. When the first indication information indicates not to maintain the PDCP replication function of the first RB in the source network device, the terminal device cannot transmit data with the source network device through the first RLC entity after the above-mentioned handover is initiated.

[0132] For example, Figure 7 As shown, Figure 7 (a) shows the first PDCP entity associated with the first RB and the RLC entity associated with the first PDCP entity before the handover is initiated (i.e., the RLC entity associated with the first RB configured by the first configuration information). Among them, RLC1 is the RLC entity corresponding to the source network device, and RLC2 is the RLC entity corresponding to the target network device (i.e., the first RLC entity). If the value of the first indication information is the first value, then after the above-mentioned handover is initiated, the terminal device can transmit data with the source network device through RLC1 and RLC2. For example, the PDCP entity of the terminal device uses the first key to encrypt the PDCP data PDU and delivers the encrypted PDCP data PDU to RLC1 and RLC2; if the value of the first indication information is the second value, then during the period from the initiation of the handover to the completion of the handover, the terminal device can only transmit data with the source network device through RLC1. Specifically, the PDCP entity of the terminal device uses the first key to encrypt the PDCP data PDU and delivers the encrypted PDCP data PDU to RLC1.

[0133] S607. Optionally, the source network device sends second configuration information to the terminal device, and correspondingly, the terminal device receives the second configuration information from the target network device, and the above-mentioned second configuration information is used to configure the PDCP duplication function of the first RB in the target network device. Exemplarily, the PDCP duplication function of the first RB in the target network device can be understood as: the CA duplication function of the first RB in the target network device. Optionally, the second configuration information can be carried on an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message. Optionally, the second configuration information and the above-mentioned first configuration information are carried on the same or different messages. Optionally, the second configuration information and the above-mentioned third configuration information are carried on the same or different messages. In an embodiment of the present application, the first configuration information, the second configuration information and the third configuration information can be sent simultaneously or separately. The embodiment of the present application does not limit the order in which the first configuration information, the second configuration information and the third configuration information are sent.

[0134] Optionally, before sending the second configuration information to the terminal device, the source network device receives a handover request confirmation message from the target network device (as shown in S604), where the handover request confirmation message includes the second configuration information. In other words, the source network device forwards the second configuration information from the target network device to the terminal device. Optionally, the second configuration information can be carried in the RRC reconfiguration message in S605.

[0135] Exemplarily, the second configuration information includes one or more of the following parameters:

[0136] 1. Identification of the first RB.

[0137] 2. The identifier of the primary RLC entity associated with the first RB. The first RB is associated with an RLC entity, and the primary RLC entity cannot be dynamically deactivated. Optionally, the terminal device can transmit PDCP control PDUs to the network device via the primary RLC entity.

[0138] 3. The identifier of the secondary RLC entity associated with the first RB. The first RB can be associated with one or more secondary RLC entities, and the secondary RLC entity can be dynamically deactivated. Optionally, the terminal device cannot transmit PDCP control PDUs through the secondary RLC entity, but can transmit PDCP data PDUs replicated by the PDCP layer through the secondary RLC entity.

[0139] After the terminal device receives the above-mentioned second configuration information, the terminal device focuses on configuring the PDCP entity associated with the first RB. In the embodiment of the present application, reconfiguring the PDCP entity associated with the first RB can also be understood as: re-establishing the PDCP entity associated with the first RB, and the new PDCP entity is the second PDCP entity. In the embodiment of the present application, for the convenience of description, the PDCP entity associated with the first RB (i.e., the second PDCP entity) is re-established for explanation.

[0140] In the embodiment of the present application, before the above-mentioned handover is completed, the second PDCP entity is in a suspended state. Only after the above-mentioned handover is completed, the second PDCP entity will replace the first PDCP entity to perform the functions of the PDCP entity. It should be understood that the second PDCP entity can also be the PDCP entity after the first PDCP entity is reconfigured using the second configuration information. There is no substantial difference between the two methods.

[0141] Optionally, the second PDCP entity may establish an encryption function applicable to the target network device, that is, the second PDCP entity uses a key applicable to the target station (hereinafter referred to as the second key) to encrypt and decrypt data packets received by the second PDCP entity. Optionally, the first key and the second key may be the same or different. Optionally, the second PDCP entity may establish an integrity protection function applicable to the target network device. Optionally, the second PDCP entity may also establish a header compression function applicable to the target network device.

[0142] The terminal device will also establish a new RLC entity associated with the first RB (i.e., the RLC entity associated with the second PDCP). In an embodiment of the present application, before the above-mentioned handover is completed, the RLC entity associated with the second PDCP is in a suspended state. Only after the above-mentioned handover is completed, the RLC entity associated with the second PDCP entity will replace the RLC entity associated with the first PDCP to perform the functions of the RLC entity.

[0143] Figure 7 (b) shows the second PDCP entity associated with the first RB and the RLC entity associated with the second PDCP entity after the handover is completed. Among them, RLC3 and RLC4 are both RLC entities corresponding to the target network device. Optionally, the initial state of the CAduplication function of RLC3 and RLC4 is deactivated, that is, before the above-mentioned CA duplication function is activated, the terminal device cannot perform data transmission based on CA duplication through RLC3 and RLC4. Optionally, before the above-mentioned handover is completed, the state of RLC3 and RLC4 is deactivated, that is, before the above-mentioned handover is completed, the terminal device cannot perform data transmission with the target network device through RLC3 and RLC4.

[0144] When the above-mentioned switching is completed, the terminal device activates the PDCP duplication function (i.e., CA duplication function) of the first RB on the target network device. Exemplarily, the terminal device activates the PDCP duplication function of the first RB on the target network device, specifically including: the terminal device activates the RLC entity corresponding to the target network device associated with the first RB. Specifically, the terminal device activates the PDCP duplication function of the first RB on the target network device in the following two ways:

[0145] Mode 1: The target network device sends a second instruction message to the terminal device, and the terminal device receives the second instruction message from the target network device. The second indication information of the target network device. The second indication information is used to activate the PDCP replication of the first RB in the target network device. Control function.

[0146] by Figure 7 Taking (b) as an example, after receiving the second indication information, the terminal device activates RLC3 and RLC4, that is, the terminal device can perform data transmission with the target network device through RLC3 and RLC4. Optionally, the second indication information is MAC CE.

[0147] Method 2: After the above switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device. able.

[0148] For example, when the above-mentioned switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device. It can also be understood that when the terminal device believes that the above-mentioned switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device.

[0149] In one possible manner, after the terminal device deems that the random access process between the terminal device and the target network device is successful, the PDCP replication function of the first RB is activated in the target network device. For example, when the terminal device uses the two-step random access method to perform random access with the target network device, when the terminal device receives message B from the target network device (message B includes one or more of an RRC establishment message and an RRC recovery message), the RRC layer of the terminal device deems that the random access process is successful by parsing message B, and the RRC layer of the terminal device instructs the PDCP layer to activate the PDCP replication function of the first RB in the target network device; when the terminal device uses the four-step random access method to perform random access with the target network device, when the terminal device receives message 4 from the target network device (message 4 includes one or more of an RRC establishment message and an RRC recovery message), and the RRC layer of the terminal device deems that the random access process is successful by parsing message 4, the RRC layer of the terminal device instructs the PDCP layer to activate the PDCP replication function of the first RB in the target network device.

[0150] Another possible way is that after the terminal device sends a handover completion message (i.e., the RRC reconfiguration completion message in S507) to the target network device on the time-frequency resources of the target network device, it is considered that the above handover has been completed. At this time, the terminal device activates the PDCP replication function of the first RB in the target network device. Optionally, this method can be applied to handover with random access, that is, after the terminal device successfully completes the random access process with the target network device ( Figure 5 S506 in the example), sending a handover completion message to the target network device ( Figure 5 S507 in); This method can also be applied to random access-less switching (RandomAccess-less, RACH-less), that is, after the target network device allows the terminal device to access ( Figure 5 In S504), the terminal device does not initiate a random access process with the target network device, but the target network device directly allocates time-frequency resources to the terminal device, and the terminal device sends a switching completion message to the target network device on the time-frequency resources.

[0151] Through the method in implementation mode 2, the terminal device can determine whether the switching is completed. When the terminal device believes that the switching is completed, the terminal device can immediately activate the PDCP replication function of the first RB in the target network device, so that the terminal device can perform PDCP replication-based data transmission with the source network device before the switching is completed. After the switching is completed, the terminal device can immediately perform PDCP replication-based data transmission with the target network device, so that the data transmission based on PDCP replication is not interrupted due to the switching, thereby improving the reliability of data transmission.

[0152] It is understandable that when the above-mentioned switching is completed, the terminal device no longer transmits the data of the first RB to the source network device through the RLC entity corresponding to the source network device. After the terminal device activates the RLC entity corresponding to the target network device associated with the first RB using but not limited to the methods in the above-mentioned methods 1 and 2, the terminal device transmits the data of the first RB to the target network device through the RLC entity corresponding to the target network device associated with the first RB. For example, the terminal device submits the data packet of the first RB (corresponding to the key of the target network device) to the RLC entity corresponding to the target network device (i.e., the RLC entity associated with the second PDCP entity). Figure 7 The data packet may be a PDCP control PDU and / or a PDCP data PDU, and the data packet may be a newly transmitted data packet or a retransmitted data packet.

[0153] The above embodiment provides a data transmission method. When a terminal device switches from a source network device to a target network device, the source network device instructs the terminal device whether to continue using the RLC entity corresponding to the target network device to transmit data on a first RB with the source network device during the period between the initiation of the handover and the completion of the handover. For services with higher reliability requirements, such as services carried by the first RB being URLLC services, the source network device may instruct the terminal device to continue using the RLC entity corresponding to the target network device before the handover is initiated to transmit data on the first RB with the source network device during the period between the initiation of the handover and the completion of the handover. This ensures that during the handover process, the terminal device can transmit the same data packet replicated at the PDCP layer to the network device via at least two RLC entities, thereby achieving zero millisecond interruption of the PDCP replication function for the URLLC service during the handover process and improving the reliability of the URLLC service during the handover process. For services with lower reliability requirements, such as services carried by the first RB being eMBB services, the source network device may instruct the terminal device to stop using the RLC entity corresponding to the target network device before the handover is initiated to transmit data on the first RB with the source network device after the handover is initiated. By implementing the above method, the source network device can flexibly indicate the data transmission method for services with different reliability requirements during handover, thereby improving data transmission flexibility. In addition, by implementing the above method, after the switching is completed, the terminal device can immediately use the PDCP replication function to transmit the data of the first RB with the target network device, so that the terminal device can still use the PDCP replication function to transmit the data of the first RB with the network device after switching to the target network device, thereby improving the reliability of data transmission.

[0154] Optional, in Figure 6 In the illustrated embodiment, S607 may be replaced by S607a.

[0155] S607a. Optionally, the source network device sends second configuration information to the terminal device, and correspondingly, the terminal device receives the second configuration information from the target network device, where the second configuration information is used to configure the PDCP duplication function of the first RB in the target network device. The PDCP duplication function of the first RB in the target network device can be understood as the CA duplication function of the first RB in the target network device. Optionally, the second configuration information can be carried on an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message. Optionally, the second configuration information and the first configuration information can be carried on the same or different messages.

[0156] Optionally, before sending the second configuration information to the terminal device, the source network device receives a handover request confirmation message from the target network device (as shown in S604), where the handover request confirmation message includes the second configuration information. In other words, the source network device forwards the second configuration information from the target network device to the terminal device. Optionally, the second configuration information can be carried on the RRC reconfiguration message in S605.

[0157] Exemplarily, the second configuration information includes an identifier of the first RB. The second configuration information also includes any one of the following parameters:

[0158] 1. Identification of the primary RLC entity associated with the first RB. For example, the first RB is associated with an RLC entity, and the primary RLC entity cannot be dynamically deactivated. Optionally, the terminal device can transmit PDCP control PDUs to the network device through the primary RLC entity.

[0159] 2. Identifier of the secondary RLC entity associated with the first RB. The first RB can be associated with one or more secondary RLC entities. The secondary RLC entity can be dynamically deactivated. Optionally, the terminal device cannot transmit PDCP control PDUs through the secondary RLC entity, but can transmit PDCP data PDUs replicated by the PDCP layer through the secondary RLC entity.

[0160] After receiving the second configuration information, the terminal device focuses on configuring the PDCP entity associated with the first RB. Reconfiguring the PDCP entity associated with the first RB can also be understood as re-establishing the PDCP entity associated with the first RB, where the new PDCP entity is the second PDCP entity. In the embodiment of the present application, for ease of description, the PDCP entity associated with the first RB (i.e., the second PDCP entity) is re-established for illustration.

[0161] Optionally, the second PDCP entity may establish an encryption function applicable to the target network device, that is, the second PDCP entity uses a key applicable to the target station (hereinafter referred to as the second key) to encrypt and decrypt data packets received by the second PDCP entity. Optionally, the first key and the second key may be the same or different. Optionally, the second PDCP entity may establish an integrity protection function applicable to the target network device. Optionally, the second PDCP entity may also establish a header compression function applicable to the target network device.

[0162] The source network device also sends third indication information to the terminal device, and correspondingly, the terminal device receives the third indication information from the source network device. For example, the third indication information indicates whether the first RLC entity is the RLC entity corresponding to the target network device after the above-mentioned handover is completed, wherein the first RLC entity is the RLC entity corresponding to the target network device before the above-mentioned handover is initiated. In other words, the third indication information is used to indicate whether the terminal device associates the first RLC entity with the second PDCP. Optionally, the third indication information can be carried on an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message.

[0163] In an optional manner, if the value of the third indication information is a third value, the terminal device associates the first RLC entity with the second PDCP; if the value of the third indication information is a fourth value, the terminal device does not associate the first RLC entity with the second PDCP. Exemplarily, the third value may be "true" or "enabled", and the fourth value may be "false" or "disabled".

[0164] In another optional manner, the third indication information and the first indication information are the same message. When the value of the first indication information is the first value, it indicates that the terminal device associates the first RLC entity with the second PDCP; when the value of the first indication information is the second value, it indicates that the terminal device does not associate the first RLC entity with the second PDCP.

[0165] The terminal device establishes a new RLC entity associated with the first RB (i.e., the RLC entity associated with the second PDCP) according to the second configuration information and the third indication information. In an embodiment of the present application, before the above-mentioned switching is completed, the RLC entity associated with the second PDCP is in a suspended state. Only after the above-mentioned switching is completed, the RLC entity associated with the second PDCP entity will replace the RLC entity associated with the first PDCP to perform the functions of the RLC entity.

[0166] For example, Figure 9 As shown, Figure 9 (a) shows the first PDCP entity associated with the first RB and the RLC entity associated with the first PDCP entity before the handover is initiated (i.e., the first PDCP entity configured for the terminal device by the first configuration information and the RLC entity associated with the first PDCP entity). RLC1 is the RLC entity corresponding to the source network device, and RLC2 is the RLC entity corresponding to the target network device (i.e., the first RLC entity).

[0167] When the third indication information instructs the terminal device to associate the first RLC entity with the second PDCP, the new RLC entities established by the terminal device for the first RB association are RLC2 and RLC3 (such as Figure 9(b) in the figure). After the above-mentioned handover is completed, the terminal device can use RLC2 and RLC3 to perform CA duplication-based data transmission with the target network device. The initial state of the CA duplication function of RLC2 and RLC3 on the target network device is deactivated, that is, before the CA duplication function is activated, the terminal device cannot perform CA duplication-based data transmission with the target network device through RLC2 and RLC3. Optionally, before the above-mentioned handover is completed, the state of RLC3 is deactivated, that is, the terminal device cannot perform data transmission with the target network device through RLC3.

[0168] After the above handover is completed, the terminal device activates the PDCP duplication function (i.e., CA duplication function) of the first RB on the target network device. For example, after the above handover is completed, the terminal device activates the RLC entity associated with the first RB and corresponding to the target network device. There are two ways for the terminal device to activate the PDCP duplication function of the first RB on the target network device:

[0169] Mode 1: The target network device sends a second instruction message to the terminal device, and the terminal device receives the second instruction message from the target network device. The second indication information of the target network device. The second indication information is used to activate the PDCP replication of the first RB in the target network device. Control function.

[0170] by Figure 9 Taking (b) as an example, after receiving the second indication information, the terminal device activates RLC2 and RLC3, that is, the terminal device can perform data transmission with the target network device through RLC2 and RLC3. Optionally, the second indication information is MAC CE.

[0171] Method 2: After the above switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device. able.

[0172] For example, when the above-mentioned switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device. It can also be understood that when the terminal device believes that the above-mentioned switching is completed, the terminal device activates the PDCP replication function of the first RB in the target network device.

[0173] For example, for a detailed description of Mode 2, refer to the description of Mode 2 in S607. Through the method in Implementation 2, the terminal device can determine whether the handover is completed. When the terminal device believes that the handover is completed, the terminal device can immediately activate the PDCP replication function of the first RB in the target network device, so that the terminal device can perform PDCP replication-based data transmission with the source network device before the handover is completed. After the handover is completed, the terminal device can immediately perform PDCP replication-based data transmission with the target network device, thereby ensuring that the PDCP replication-based data transmission is not interrupted due to the handover, thereby improving the reliability of data transmission.

[0174] It is understandable that after the above handover is completed, the terminal device no longer uses the RLC entity associated with the source network device (for example, Figure 9 After the terminal device activates the RLC entity corresponding to the target network device associated with the first RB using but not limited to the methods in the above-mentioned method 1 and method 2, the terminal device transmits the data of the first RB to the target network device through the RLC entity corresponding to the target network device associated with the first RB. Exemplarily, the terminal device delivers a data packet encrypted using the secret key of the target network device to the RLC entity corresponding to the target network device associated with the first RB. The RLC entity corresponding to the target network device associated with the first RB includes a first RLC entity (exemplarily, Figure 9 The first RLC entity corresponds to RLC2). The RLC entity corresponding to the target network device also includes a second RLC entity, wherein the second RLC entity is other RLC entities except the first RLC entity among the RLC entities corresponding to the target network device associated with the first RB (exemplarily, in Figure 9 The second RLC entity corresponds to RLC3). Optionally, the above-mentioned data packet may be a PDCP control PDU and / or a PDCP data PDU, and the data packet may be a newly transmitted data packet or a retransmitted data packet.

[0175] For downlink transmission, before the handover is completed, the data transmitted by the source network device to the terminal device through the first RLC entity is encrypted using the first key. After the handover is completed, the data transmitted by the target network device to the terminal device through the first RLC entity is encrypted using the second key. When there is a discrepancy between the terminal device and the network device in their judgment of the moment when the handover is completed, the terminal device cannot know whether the data received by the first RLC entity is encrypted using the first key or the second key. To solve this problem, the present application provides two optional methods:

[0176] Method 1: The source network device sends fourth indication information to the terminal device, and the terminal device receives the fourth indication information from the source network device. The fourth indication information instructs the terminal device to encrypt all data received after receiving the fourth indication information using the second key. Optionally, the fourth indication information can be an RRC message or a MAC CE.

[0177] Method 2: The terminal device maintains a timer and starts the timer when the terminal device determines that the above-mentioned switching is completed. When the timer expires, the terminal device considers that all data received after the timer expires to be encrypted using the second key. Optionally, the duration of the timer is preset.

[0178] By implementing the method of S607a, by converting the RLC entity corresponding to the target network device before the handover is initiated (the first RLC entity) into the RLC entity corresponding to the target network device after the handover is completed, the terminal device can perform PDCP replication-based data transmission with the target network device through the first RLC entity and the RLC entity other than the first RLC entity (the second RLC entity) among the RLC entities corresponding to the target network device after the handover is completed. This ensures that the PDCP replication-based data transmission of the first RB is not interrupted due to the handover, thereby improving the reliability of data transmission. At the same time, in this way, the target network device only needs to configure the second RLC entity, and the terminal device can perform PDCP replication-based data transmission with the target network device, thereby reducing the overhead of resource configuration.

[0179] Optional, in Figure 6 In the illustrated embodiment, S607 may also be replaced by S607b.

[0180] S607b. Optionally, the source network device sends second configuration information to the terminal device. Correspondingly, the terminal device receives the second configuration information from the target network device. The second configuration information is used to configure the RLC entity corresponding to the target network device and associated with the first RB. Optionally, the second configuration information may be carried in an RRC reconfiguration message, an RRC establishment message, or an RRC recovery message. Optionally, the second configuration information and the first configuration information may be carried in the same or different messages.

[0181] After receiving the second configuration information, the terminal device focuses on configuring the PDCP entity associated with the first RB. Reconfiguring the PDCP entity associated with the first RB can also be understood as re-establishing the PDCP entity associated with the first RB, where the new PDCP entity is the second PDCP entity. In the embodiment of the present application, for ease of description, the PDCP entity associated with the first RB (i.e., the second PDCP entity) is re-established for illustration.

[0182] Optionally, the second PDCP entity may establish an encryption function applicable to the target network device, that is, the second PDCP entity uses a key applicable to the target station (hereinafter referred to as the second key) to encrypt and decrypt data packets received by the second PDCP entity. Optionally, the first key and the second key may be the same or different. Optionally, the second PDCP entity may establish an integrity protection function applicable to the target network device. Optionally, the second PDCP entity may also establish a header compression function applicable to the target network device.

[0183] The terminal device will also establish a new RLC entity associated with the first RB (i.e., the RLC entity associated with the second PDCP). In an embodiment of the present application, before the above-mentioned handover is completed, the RLC entity associated with the second PDCP is in a suspended state. Only after the above-mentioned handover is completed, the RLC entity associated with the second PDCP entity will replace the RLC entity associated with the first PDCP to perform the functions of the RLC entity.

[0184] For example, Figure 10 As shown, Figure 10 (a) shows the first PDCP entity associated with the first RB and the RLC entity associated with the first PDCP entity before the handover is initiated, where RLC1 is the RLC entity corresponding to the source network device, and RLC2 is the RLC entity corresponding to the target network device (i.e., the first RLC entity). Figure 10 (b) shows the second PDCP entity associated with the first RB and the RLC entity associated with the second PDCP entity (i.e., RLC3) after the handover is completed. Before the handover is completed, the state of RLC3 is deactivated, that is, the terminal device cannot perform data transmission with the target network device through RLC3.

[0185] When the above handover is completed, the terminal device activates the RLC entity corresponding to the target network device. For example, there are two ways for the terminal device to activate the RLC entity corresponding to the target network device:

[0186] Mode 1: The target network device sends a second instruction message to the terminal device, and the terminal device receives the second instruction message from the target network device. The second indication information of the target network device is used to activate the RLC entity corresponding to the target network device.

[0187] by Figure 10 For example, after receiving the second indication information, the terminal device activates RLC3, that is, the terminal device can perform data transmission with the target network device through RLC3. Optionally, the second indication information is MAC CE.

[0188] Method 2: After the above switching is completed, the terminal device activates the RLC entity corresponding to the target network device.

[0189] Exemplarily, when the above-mentioned switching is completed, the terminal device activates the RLC entity corresponding to the target network device. It can also be understood that when the terminal device believes that the above-mentioned switching is completed, the terminal device activates the RLC entity corresponding to the target network device.

[0190] In one possible approach, after the terminal device deems that the random access process between the terminal device and the target network device is successful, the terminal device activates the RLC entity corresponding to the target network device. For example, after the random access is successful, the MAC layer of the terminal device indicates to the RRC layer that the uplink data switching has been completed.

[0191] Another possible approach is that after the terminal device sends a handover completion message (i.e., an RRC reconfiguration completion message) to the target network device on the time-frequency resources of the target network device, it considers that the uplink data handover has been completed. At this time, the terminal device activates the RLC entity corresponding to the target network device. Optionally, this approach can be applicable to handovers with random access or without random access. For details about handovers with random access and without random access, please refer to the description of S607.

[0192] Through the method in implementation mode 2, the terminal device can determine whether the switching is completed. When the terminal device believes that the switching is completed, the terminal device immediately activates the RLC entity corresponding to the target network device, so that the terminal device can perform data transmission based on PDCP replication with the source network device before the switching is completed. After the switching is completed, the terminal device can immediately perform data transmission with the target network device, thereby improving the reliability of data transmission.

[0193] After the terminal device activates the RLC entity corresponding to the target network device associated with the first RB using the method in but not limited to the above-mentioned method 1 and method 2, the terminal device submits a data packet encrypted using the secret key of the target network device to the second RLC entity, wherein the second RLC entity is an RLC entity other than the first RLC entity in the RLC entity corresponding to the target network device (exemplarily, in Figure 10 The second RLC entity corresponds to RLC3. The above data packet may be a PDCP control PDU and / or a PDCP data PDU, and the data packet may be a newly transmitted data packet or a retransmitted data packet.

[0194] Optionally, the terminal device submits a data packet encrypted using the key of the source network device to the first RLC entity. After receiving the PDCP PDU from the first RLC entity, the PDCP entity of the source network device converts the PDCP PDU into a PDCP SDU and forwards it to the target network device.

[0195] By implementing the method of S607b, after the switching is completed, for uplink transmission, the PDCP entity of the terminal device will copy the data into two copies. One copy can be sent to the source network device through the RLC entity (first RLC entity) corresponding to the target network device before the switching is initiated, and then forwarded to the target network device through the Xn interface by the source network device. The other copy can be sent directly to the target network device through the RLC entity (second RLC entity) corresponding to the target network device after the switching is completed, thereby improving the reliability of data transmission. For downlink transmission, the source network device and the target network device can send the same data to the terminal: the PDCP entity of the source network device converts a PDCP SDU into a PDCP PDU and sends it to the terminal device through the first RLC entity. The source network device can also forward another identical PDCP SDU to the target network device via the Xn interface. The PDCP entity of the target network device converts the PDCP SDU into a PDCP PDU and sends it to the terminal device through the second RLC entity; or, the PDCP entity of the target network device converts a PDCP SDU into a PDCP PDU and sends it to the terminal device through the second RLC entity. The target network device can also forward another identical PDCP SDU to the source network device via the Xn interface. The PDCP entity of the source network device converts the PDCP SDU into a PDCP PDU and sends it to the terminal device through the first RLC entity, thereby improving the reliability of data transmission.

[0196] It is understandable that in order to implement the functions in the above embodiments, the network devices and terminal devices include hardware structures and / or software modules corresponding to the execution of each function. It should be readily apparent to those skilled in the art that, in combination with the units and method steps of each example described in the embodiments disclosed in this application, the present application can be implemented in the form of hardware, software, or a combination of hardware and software. Whether a function is executed in the form of hardware, software, or computer software driving hardware depends on the specific application scenario and design constraints of the technical solution.

[0197] Figure 11 and Figure 12 Schematic diagram of the structure of possible communication devices provided in the embodiments of the present application. These communication devices can be used to implement the functions of the terminal device or source network device in the above method embodiments, and thus can also achieve the beneficial effects possessed by the above method embodiments. In the embodiments of the present application, the communication device can be as follows Figure 1 The terminal device 110 shown may also be Figure 1 The network device 120 or the network device 130 shown may also be a module (such as a chip) applied to a terminal device or a network device.

[0198] like Figure 11As shown, the communication device 1100 includes a processing unit 1110 and a transceiver unit 1120. The communication device 1100 is used to implement the above Figure 6 Alternatively, the communication device 1100 may include a method for implementing the above Figure 6 In the method embodiment shown in FIG, any function or operation module of the terminal device or the source network device can be implemented in whole or in part by software, hardware, firmware or any combination thereof.

[0199] When the communication device 1100 is used to implement Figure 6 When the function of the terminal device in the method embodiment shown is performed, the transceiver unit 1120 is used to receive first configuration information from the source network device, and the first configuration information is used to configure the packet data convergence protocol PDCP replication function of the first radio bearer RB of the terminal device in the source network device; the transceiver unit 1120 is also used to receive first indication information from the source network device, and the first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device when the terminal device switches from the source network device to the target network device; the transceiver unit 1120 is also used to transmit data of the first RB with the source network device according to the above-mentioned first indication information.

[0200] When the communication device 1100 is used to implement Figure 6 In the method embodiment shown, when the source network device functions, the transceiver unit 1120 is used to send first configuration information to the terminal device, and the first configuration information is used to configure the packet data convergence protocol PDCP replication function of the first radio bearer RB of the terminal device in the source network device; the transceiver unit 1120 is also used to send first indication information to the terminal device, and the first indication information indicates whether to maintain the PDCP replication function of the first RB in the source network device when the terminal device switches from the source network device to the target network device; the transceiver unit 1120 is also used to transmit data of the first RB with the source network terminal device according to the above-mentioned first indication information.

[0201] For more detailed description of the processing unit 1110 and the transceiver unit 1120, please refer to Figure 6 The relevant description in the method embodiment shown is directly obtained and will not be repeated here.

[0202] like Figure 12As shown, communication device 1200 includes a processor 1210 and an interface circuit 1220. Processor 1210 and interface circuit 1220 are coupled to each other. It will be appreciated that interface circuit 1220 may be a transceiver or an input / output interface. Optionally, communication device 1200 may further include a memory 1230 for storing instructions executed by processor 1210, input data required by processor 1210 to execute instructions, or data generated after processor 1210 executes instructions.

[0203] When the communication device 1200 is used to implement Figure 6 When the method shown is used, the processor 1210 is used to implement the functions of the above-mentioned processing unit 1110, and the interface circuit 1220 is used to implement the functions of the above-mentioned transceiver unit 1120.

[0204] When the communication device is a chip used in a terminal device, the terminal device chip implements the functions of the terminal device in the above method embodiments. The terminal device chip receives information from other modules in the terminal device (such as a radio frequency module or antenna), and the information is sent by the network device to the terminal device; or the terminal device chip sends information to other modules in the terminal device (such as a radio frequency module or antenna), and the information is sent by the terminal device to the network device.

[0205] When the communication device is a chip used in a network device, the network device chip implements the network device functions of the above method embodiments. The network device chip receives information from other modules in the network device (such as a radio frequency module or antenna), and the information is sent by the terminal device to the network device; or the network device chip sends information to other modules in the network device (such as a radio frequency module or antenna), and the information is sent by the network device to the terminal device.

[0206] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0207] In the embodiments of the present application, the processor can 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 mobile hard disk, a CD-ROM, or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a network device or a terminal device. Of course, the processor and the storage medium can also exist in a network device or a terminal device as discrete components.

[0208] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instruction is loaded and executed on a computer, the process or function described in the embodiment of the present application is executed in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, a network device, a terminal device, or other programmable device. The computer program or instruction may be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server that integrates one or more available media. The available medium may be a magnetic medium, such as a floppy disk, a hard disk, or a tape; it may also be an optical medium, such as a DVD; it may also be a semiconductor medium, such as a solid state disk (SSD).

[0209] In the various embodiments of the present application, unless otherwise specified or there is a logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0210] It is understood that the various numbers used in the embodiments of this application are merely for ease of description and are not intended to limit the scope of the embodiments of this application. The order of the sequence numbers of the above-mentioned processes does not necessarily imply a specific order of execution; the order of execution of the processes should be determined by their functions and inherent logic.

Claims

1. A data transmission method, characterized in that: The method is applied to a terminal device switching from a source network device to a target network device, and the method includes: Receive first configuration information from the source network device, where the first configuration information is used to configure a packet data convergence protocol (PDCP) replication function of a first radio bearer (RB) of the terminal device in the source network device; receiving first indication information from the source network device, where the first indication information indicates whether to maintain a PDCP replication function of the first RB on the source network device when the terminal device switches from the source network device to the target network device; Transmit data of the first RB with the source network device according to the first indication information.

2. The method according to claim 1, characterized in that The maintaining of the PDCP copy function of the first RB in the source network device specifically includes: Maintain a first radio link control RLC entity, where the first RLC entity is the RLC entity corresponding to the target network device before the handover is initiated.

3. The method according to claim 1 or 2, characterized in that When the first indication information indicates to maintain the PDCP replication function of the first RB on the source network device, transmitting data of the first RB with the source network device according to the first indication information specifically includes: When the handover is initiated, a data packet encrypted using the secret key of the source network device is delivered to the first RLC entity.

4. The method according to claim 1 or 2, characterized in that The method further comprises: receiving second configuration information from the source network device, where the second configuration information is used to configure a PDCP replication function of the first RB in the target network device; When the handover is completed, the PDCP replication function of the first RB in the target network device is activated.

5. The method according to claim 1 or 2, characterized in that The method further comprises: receiving second configuration information from the source network device, where the second configuration information is used to configure a PDCP replication function of the first RB in the target network device; Second indication information is received from the target network device, where the second indication information is used to activate a PDCP duplication function of the first RB in the target network device.

6. The method according to claim 4, characterized in that The activating the PDCP replication function of the first RB in the target network device specifically includes: activating an RLC entity associated with the first RB and corresponding to the target network device.

7. The method according to claim 4, characterized in that The first indication information further indicates that when the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device.

8. The method according to claim 7, characterized in that After the switching is completed, the method further includes: The data packet encrypted using the secret key of the target network device is delivered to the first RLC entity.

9. The method according to claim 2, characterized in that After the switching is completed, the method further includes: The data packet encrypted using the key of the source network device is delivered to the first RLC entity.

10. The method according to claim 8 or 9, characterized in that The method further comprises: Submit a data packet encrypted using the secret key of the target network device to the second RLC entity, where the second RLC entity is an RLC entity in the RLC entity associated with the first RB, and the second RLC entity is the RLC entity corresponding to the target network device after the handover is completed.

11. A data transmission method, characterized in that: The method is applied to switching a terminal device from a source network device to a target network device, and the method includes: Sending first configuration information to the terminal device, where the first configuration information is used to configure a packet data convergence protocol PDCP replication function of a first radio bearer RB of the terminal device in the source network device; Sending first indication information to the terminal device, where the first indication information indicates whether to maintain a PDCP replication function of the first RB on the source network device when the terminal device switches from the source network device to the target network device; Transmit data of the first RB to the terminal device according to the first indication information.

12. The method according to claim 11, characterized in that The maintaining of the PDCP copy function of the first RB in the source network device specifically includes: Maintain a first radio link control RLC entity, where the first RLC entity is the RLC entity corresponding to the target network device before the handover is initiated.

13. The method according to claim 11 or 12, characterized in that When the first indication information indicates to maintain the PDCP replication function of the first RB on the source network device, transmitting data of the first RB with the terminal device according to the first indication information specifically includes: When the handover is initiated, a data packet encrypted using the key of the source network device is received from the first RLC entity.

14. The method according to claim 11 or 12, characterized in that The method further comprises: Send second configuration information to the terminal device, where the second configuration information is used to configure the PDCP replication function of the first RB in the target network device.

15. The method according to claim 14, characterized in that The first indication information further indicates that when the handover is completed, the first RLC entity is the RLC entity corresponding to the target network device.

16. The method according to claim 11 or 12, characterized in that After the switching is completed, the method further includes: receiving a data packet encrypted using a key of the source network device from the first RLC entity; The data packet encrypted using the secret key of the source network device is forwarded to the target network device.

17. A communication device, characterized in that: Comprising means for performing the method according to any one of claims 1 to 10.

18. A communication device, characterized in that: Comprising means for performing the method as claimed in any one of claims 11 to 16.

19. A communication device, characterized in that: The method comprises a processor and a memory, wherein the processor and the memory are coupled, and the processor is configured to implement the method according to any one of claims 1 to 10.

20. A communication device, characterized in that: The method comprises a processor and a memory, wherein the processor and the memory are coupled, and the processor is configured to implement the method according to any one of claims 11 to 16.

21. A communication device, characterized in that: The method comprises a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method according to any one of claims 1 to 10 through a logic circuit or executing code instructions.

22. A communication device, characterized in that: The method comprises a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method as described in any one of claims 11 to 16 through a logic circuit or executing code instructions.

23. A computer-readable storage medium, characterized in that The storage medium stores a computer program or instruction. When the computer program or instruction is executed by the communication device, the method according to any one of claims 1 to 10 is implemented, or the method according to any one of claims 11 to 16 is implemented.

24. A communication system, characterized in that: The method comprises the communication device according to any one of claims 17, 19, and 21, and the communication device according to any one of claims 18, 20, and 22.

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