Communication method and apparatus

Abstract

The present application relates to the technical field of communications, and discloses a communication method and apparatus. The method comprises: a first network device receives a first message from a second network device, the first message being used for requesting the first network device to perform advance synchronization for carrier aggregation, a primary cell of carrier aggregation being a first cell, a secondary cell of carrier aggregation comprising a second cell, and the advance synchronization comprising advance uplink synchronization and / or advance downlink synchronization; and the first network device sends first instruction information to a terminal on the basis of the first message, the first instruction information being used for instructing the terminal and the second cell to perform advance synchronization. By using the method, advance synchronization for carrier aggregation is executed in a cell switching scenario, so that after the terminal is switched to the first cell, data transmission can be quickly carried out in a carrier aggregation mode, thereby ensuring high-rate data transmission.

Description

Communication method and device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on October 31, 2023, with application number 202311444145.6 and application name “A Communication Method and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of communication technology, and in particular to a communication method and device. Background Art

[0004] Cell switching is a very important feature in communication systems. It mainly involves the network equipment switching the terminal device to a neighboring cell with better signal quality before the signal quality of the serving cell becomes poor, thereby providing lossless or packet loss-free communication services.

[0005] However, how to ensure high-speed data transmission in cell switching scenarios still needs further research.

[0006] Summary of the Invention

[0007] The present application provides a communication method and apparatus for achieving early synchronization of carrier aggregation, so that after a terminal switches to a primary cell of carrier aggregation, it can quickly transmit data on a secondary cell of carrier aggregation to ensure high-speed data transmission.

[0008] In a first aspect, an embodiment of the present application provides a communication method, which can be applied to a first network device or a module (such as a chip or circuit) in the first network device. Taking the application of this method to the first network device as an example, in this method, the first network device receives a first message from a second network device, and the first message is used to request the first network device to perform early synchronization for carrier aggregation, the primary cell of the carrier aggregation is the first cell, the secondary cell of the carrier aggregation includes the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; according to the first message, first indication information is sent to the terminal, and the first indication information is used to instruct the terminal to perform early synchronization with the second cell.

[0009] By adopting the above method, by performing early synchronization for carrier aggregation in the cell switching scenario, the terminal can quickly transmit data through carrier aggregation after switching to the first cell, thereby ensuring high-speed data transmission.

[0010] In one possible design, after sending the first indication information to the terminal, the method further includes: sending a switching command message to the terminal, where the switching command message is used to instruct the primary cell of the terminal to switch to the first cell.

[0011] In one possible design, the early synchronization includes uplink synchronization and / or downlink synchronization of the terminal before receiving the switching command message.

[0012] In one possible design, the first message includes identification information of the second cell, where the identification information of the second cell is used to request the first network device to perform early synchronization for the second cell. Thus, by carrying the identification information of the second cell in the first message, it is possible to clearly indicate for which cells the first network device is requested to perform early synchronization.

[0013] In one possible design, the first indication information is used to activate the transmission configuration indication TCI state of the second cell, and the TCI state is used by the terminal to determine the downlink timing of the second cell.

[0014] In one possible design, the method further includes: sending activated TCI status information of the second cell to the second network device. In this way, by sending the activated TCI status information of the second cell to the second network device, after the terminal subsequently switches to the first cell, the terminal can communicate with the DU or access network device to which the first cell belongs based on the activated TCI status of the second cell, thereby improving communication efficiency.

[0015] In one possible design, the first indication information is used to instruct the terminal to send a random access signal on the second cell, and the random access signal is used to determine the timing advance TA of the second cell.

[0016] In one possible design, the method further includes: receiving the TA of the second cell; and sending a switching command message to the terminal, wherein the switching command message includes the TA of the second cell.

[0017] In one possible design, the switching command message also includes the TA of the first cell.

[0018] In one possible design, the method further includes: sending second indication information to the second network device, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed. In this way, the DU or access network device to which the first cell belongs can be informed of whether the terminal has completed early synchronization with the second cell.

[0019] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0020] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on terminal measurement of downlink reference signals.

[0021] Generally speaking, the accuracy of synchronization based on random access is higher, while the accuracy of synchronization based on the terminal measuring the downlink reference signal is relatively low. Therefore, after the DU or access network device to which the first cell belongs receives the synchronization mode information, it can decide whether to instruct the terminal to adjust the TA of the second cell based on the synchronization mode information. For example, if the synchronization mode information indicates that the advance synchronization method is based on the terminal measuring the downlink reference signal, the DU or access network device to which the first cell belongs can subsequently instruct the terminal to adjust the TA of the second cell to improve the synchronization accuracy.

[0022] In one possible design, the method further includes: receiving channel state information CSI of the second cell sent by the terminal, where the CSI of the second cell is determined based on the first indication information; and sending the CSI of the second cell to the second network device.

[0023] In this way, since the CSI of the second cell is obtained by the terminal in advance (for example, it is measured before the terminal switches to the first cell), after the terminal switches to the first cell, the DU or access network equipment to which the first cell belongs can allocate resources to the terminal based on the CSI of the second cell measured in advance, so as to facilitate rapid data transmission in the second cell.

[0024] In a second aspect, an embodiment of the present application provides a communication method, which can be applied to a second network device or a module (such as a chip or circuit) in the second network device. Taking the application of this method to the second network device as an example, in this method, the second network device sends a first message to the first network device, and the first message is used to request the first network device to perform early synchronization for carrier aggregation, the primary cell of the carrier aggregation is the first cell, the secondary cell of the carrier aggregation includes the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; and receives a second message from the first network device, and the second message is used to indicate acceptance of the request of the first message.

[0025] In one possible design, the method further includes: receiving second indication information from the first network device or terminal, the second indication information being used to indicate that early synchronization for the carrier aggregation has been performed.

[0026] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0027] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on the terminal measuring the downlink reference signal.

[0028] In one possible design, the method further includes: receiving CSI of the second cell from the first network device or terminal, where the CSI of the second cell is determined before the terminal switches to the first cell.

[0029] In one possible design, the method further includes receiving activated TCI status information of the second cell from the first network device or terminal.

[0030] On the third aspect, an embodiment of the present application provides a communication method, which can be applied to a terminal or a module in the terminal (such as a chip or circuit). Taking the application of this method to the terminal as an example, in this method, the terminal receives configuration information of carrier aggregation, the main cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation includes the second cell; receives first indication information, and the first indication information is used to instruct the terminal to perform early synchronization with the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; according to the first indication information, early synchronization is performed with the second cell.

[0031] In one possible design, after receiving the first indication information, the method further includes: receiving a switching command message, where the switching command message is used to instruct the terminal to switch to the first cell, and the switching command message includes the TA of the second cell.

[0032] In one possible design, the method further includes: sending second indication information, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

[0033] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0034] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on the terminal measuring the downlink reference signal.

[0035] In one possible design, the method further includes: sending the CSI of the second cell, where the CSI of the second cell is determined based on the first indication information.

[0036] In one possible design, the first indication information is used to activate the transmission configuration indication TCI state of the second cell; according to the first indication information, early synchronization with the second cell is performed, including: determining the downlink timing of the second cell according to the activated TCI state of the second cell.

[0037] In one possible design, the method further includes: sending activated TCI status information of the second cell.

[0038] In one possible design, the first indication information is used to instruct the terminal to send a random access signal on the second cell; and according to the first indication information, early synchronization with the second cell is performed, including: according to the first indication information, sending a random access signal on the second cell, and the random access signal is used to determine the TA of the second cell.

[0039] It can be understood that the beneficial effects of the relevant technical features in the second and third aspects can be referred to the description of the first aspect and will not be repeated here.

[0040] In a fourth aspect, the present application provides a communication device, which has the ability to implement the functions involved in the first to third aspects above. For example, the communication device includes modules or units or means corresponding to the operations involved in the first to third aspects above. The functions or units or means can be implemented through software, or through hardware, or the corresponding software can be implemented through hardware.

[0041] In one possible design, the communication device includes a processing unit and a communication unit. The communication unit can be used to send and receive signals to enable communication between the communication device and other devices, for example, the communication unit is used to send system information to a terminal. The processing unit can be used to perform certain internal operations of the communication device. The functions performed by the processing unit and the communication unit can correspond to the operations described in the first to third aspects above.

[0042] In one possible design, the communication device includes a processor, which can be coupled to a memory. The memory can store the necessary computer programs or instructions for implementing the functions of the first to third aspects described above. The processor can execute the computer programs or instructions stored in the memory. When the computer programs or instructions are executed, the communication device implements the method of any possible design or implementation of the first to third aspects described above.

[0043] In one possible design, the communication device includes a processor and a memory, and the memory may store the necessary computer programs or instructions for implementing the functions of the first to third aspects described above. The processor may execute the computer program or instructions stored in the memory. When the computer program or instructions are executed, the communication device implements the method of any possible design or implementation of the first to third aspects described above.

[0044] In one possible design, the communication device includes a processor and an interface circuit, wherein the processor is used to communicate with other devices through the interface circuit and execute the method in any possible design or implementation of the first to third aspects above.

[0045] It can be understood that in the fourth aspect above, the processor can be implemented by hardware or by software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc.; when implemented by software, the processor can be a general-purpose processor, which is implemented by reading the software code stored in the memory. In addition, the above processors can be one or more, and the memories can be one or more. The memory can be integrated with the processor, or the memory and the processor can be set separately. In the specific implementation process, the memory can be integrated with the processor on the same chip, or can be set on different chips respectively. The embodiment of the present application does not limit the type of memory and the setting method of the memory and the processor.

[0046] In a fifth aspect, the present application provides a communication system, which may include a first network device, a second network device and a terminal; wherein the first network device is used to execute the method described in the first aspect, the second network device is used to execute the method described in the second aspect, and the terminal is used to execute the method described in the third aspect.

[0047] In a sixth aspect, the present application provides a computer-readable storage medium, in which computer-readable instructions are stored. When a computer reads and executes the computer-readable instructions, the computer executes the method in any possible design of the first to third aspects above.

[0048] In a seventh aspect, the present application provides a computer program product, which, when read and executed by a computer, enables the computer to execute the method in any possible design of the first to third aspects above.

[0049] In an eighth aspect, the present application provides a chip, comprising a processor, wherein the processor is coupled to a memory and is configured to read and execute a software program stored in the memory to implement a method in any possible design of the first to third aspects above.

[0050] These and other aspects of the present application will become more readily apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG1 is a schematic diagram of a communication system applicable to an embodiment of the present application;

[0052] FIG2A is a schematic diagram of a CU-DU separation architecture provided in an embodiment of the present application;

[0053] FIG2B is a schematic diagram of another CU-DU separation architecture provided in an embodiment of the present application;

[0054] FIG3A is a schematic diagram of a downlink timing difference provided in an embodiment of the present application;

[0055] FIG3B is a schematic diagram of timing advance provided in an embodiment of the present application;

[0056] FIG4 is a flow chart of the communication method according to the first embodiment of the present application;

[0057] FIG5 is a flow chart of the communication method according to the second embodiment of the present application;

[0058] FIG6 is a flow chart of the communication method according to the third embodiment of the present application;

[0059] FIG7 is a possible exemplary block diagram of a device involved in an embodiment of the present application;

[0060] FIG8 is a schematic diagram of the structure of a network device provided in an embodiment of the present application;

[0061] FIG9 is a schematic structural diagram of a terminal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application. The technical solutions in the embodiments of the present application can be applied to various communication systems, such as universal mobile telecommunications system (UMTS), wireless local area network (WLAN), wireless fidelity (Wi-Fi) system, 4th generation (4G) mobile communication system, such as long term evolution (LTE) system, fifth generation (5G) mobile communication system, such as new radio (NR) system, and future evolved communication systems, such as sixth generation (6G) mobile communication system.

[0063] This application will present various aspects, embodiments, or features in the context of systems that may include multiple devices, components, modules, etc. It should be understood and appreciated that each system may include additional devices, components, modules, etc., and / or may not include all of the devices, components, modules, etc. discussed in conjunction with the figures. Furthermore, combinations of these aspects may also be used.

[0064] In addition, in the embodiments of the present application, words such as "exemplarily" and "such as" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as an "example" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present concepts in a concrete way. In the embodiments of the present application, "of", "corresponding, relevant" and "corresponding" can sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings to be expressed are consistent.

[0065] The communication system and business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. A person skilled in the art will appreciate that, with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0066] To facilitate understanding of the embodiments of the present application, the communication system applicable to the embodiments of the present application is first described in detail using the communication system shown in Figure 1 as an example. As shown in Figure 1, the communication system 10 includes one or more access network devices 20, and one or more terminals 30. Among them, the interface between the access network device and the terminal can be a Uu interface (or called an air interface), and data can be transmitted between the access network device 20 and the terminal 30 through air interface resources. Exemplarily, the terminal can be located within the communication coverage of one or more cells of the access network device, and the cell providing service to the terminal (i.e., the service cell of the terminal) can be one or more. When there are multiple service cells of the terminal, the terminal can work in a carrier aggregation (CA) manner.

[0067] (1) Terminal

[0068] A terminal may be a terminal that accesses the above-mentioned communication system and has wireless transceiver functions, or a chip or chip system that can be set in the terminal. A terminal may also be called user equipment (UE), terminal equipment, user device, access terminal, user unit, user station, mobile station, mobile station (MS), remote station, remote terminal, mobile device, user terminal, terminal unit, terminal station, terminal device, wireless communication equipment, user agent or user device.

[0069] For example, the terminal in the embodiment of the present application can be a mobile phone, a personal digital assistant (PDA), a laptop computer, a tablet computer, a drone, a computer with wireless transceiver function, a machine type communication (MTC) terminal, a virtual reality (VR) terminal, an augmented reality (AR) terminal, an Internet of Things (IoT) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home (such as a game console, a smart TV, a smart speaker, a smart refrigerator, and fitness equipment, etc.), a vehicle-mounted terminal, and an RSU with terminal function.

[0070] (2) Access network equipment

[0071] The access network device is a device located on the network side of the above-mentioned communication system and has wireless transceiver functions or a chip or chip system that can be set in the device.

[0072] For example, the access network device in the embodiment of the present application can be an access point (AP) in a Wi-Fi system, such as a home gateway, a router, a server, a switch, a bridge, etc., a base station, an evolved Node B (eNB), a radio network controller (RNC), a base station controller (BSC), a base transceiver station (BTS), a home base station, a baseband unit (BBU), a wireless relay node, a wireless backhaul node, a transmission point (TRP; or a transmission point, TP), etc. It can also be a next-generation NodeB (gNB) in a 5G system, or a network node constituting a gNB, such as a centralized unit (CU), a distributed unit (DU), a roadside unit (RSU) with base station functions, etc., or it can also be a satellite or various future forms of base stations.

[0073] (3) Communication between terminals and access network equipment

[0074] Communication between a terminal and an access network device follows a specific protocol layer structure. For example, the control plane protocol layer structure may include the radio resource control (RRC) layer, the packet data convergence protocol (PDCP) layer, the radio link control (RLC) layer, the media access control (MAC) layer, and the physical layer (PHY). The user plane protocol layer structure may include the PDCP layer, the RLC layer, the MAC layer, and the physical layer. In one possible implementation, the service data adaptation protocol (SDAP) layer may also be included above the PDCP layer. The SDAP layer, PDCP layer, RLC layer, MAC layer, and physical layer may also be collectively referred to as the access layer. For detailed descriptions of each of the above protocol layers, please refer to the relevant technical specifications of the 3rd Generation Partnership Project (3GPP).

[0075] Taking downlink data transmission as an example, downlink data can be encapsulated accordingly at each layer of the access network device. The data received by a layer from the layer above it is considered a service data unit (SDU) of that layer. After layer encapsulation, it becomes a protocol data unit (PDU) and is then passed to the next layer. For example, the data received by the PDCP layer entity from the SDAP layer is called a PDCP SDU. After the PDCP layer entity encapsulates the PDCP SDU, it obtains a PDCP PDU and sends it to the RLC layer. The PDCP PDU received by the RLC layer entity from the PDCP layer is called an RLC SDU. After the RLC layer entity encapsulates the RLC SDU, it obtains an RLC PDU and sends it to the MAC layer.

[0076] From the perspective of the terminal, after the terminal's physical layer receives a transport block from the access network device, it can pass it up to the upper layer in sequence, where it can perform the corresponding decapsulation. In other words, the processing performed by each layer in the terminal can be the reverse of the processing performed by each layer in the access network device.

[0077] (4) CU-DU separation architecture

[0078] For example, in some possible network structures, the access network equipment may include one or more centralized units (CU) and one or more distributed units (DU), and multiple DUs may be centrally controlled by one CU. This architecture may be referred to as a CU-DU separation architecture. As an example, the interface between the CU and the DU may be referred to as an F1 interface, where the control plane (CP) interface may be an F1-C interface and the user plane (UP) interface may be an F1-U interface.

[0079] The processing functions of CU and DU can be divided according to the protocol layers of the wireless network: for example, as shown in Figure 2A, 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. It can be understood that the above division of the processing functions of CU and DU according to the protocol layer is only an example, and can also be divided in other ways, such as the functions of the protocol layers above the RLC layer are set in the CU, and the functions of the protocol layers of the RLC layer and below are set in the DU. For example, the CU or DU can be divided into functions with more protocol layers, and the CU or DU can also be divided into partial processing functions with protocol layers. The embodiments of the present application are not limited to this.

[0080] Furthermore, the functions of the CU can be implemented by one entity, or by different entities. For example, the functions of the CU can be further divided, that is, the control plane and the user plane are separated and implemented through different entities, namely the control plane CU entity (i.e., CU-CP entity) and the user plane CU entity (i.e., CU-UP entity). The CU-CP entity and the CU-UP entity can be coupled with the DU to jointly complete the functions of the RAN device. The interface between the CU-CP entity and the CU-UP entity can be an E1 interface, the interface between the CU-CP entity and the DU can be an F1-C interface, and the interface between the CU-UP entity and the DU can be an F1-U interface. Among them, one DU and one CU-UP can be connected to one CU-CP. Under the control of the same CU-CP, one DU can be connected to multiple CU-UPs, one CU-UP can be connected to multiple DUs, and under the collaboration of multiple CU-CPs, one CU-UP can also be connected to multiple cooperating CU-CPs, thereby improving the flexibility of the CU-CP. Figure 2B is a schematic diagram of an air interface protocol stack distribution. As shown in FIG2B , for both the user plane and the control plane, the air interface protocol stack may be RLC, MAC, and PHY in the DU, and PDCP and above protocol layers in the CU.

[0081] It should be noted that: in the architecture shown in Figures 2A and 2B above, the signaling generated by the CU can be sent to the terminal through the DU, or the signaling generated by the terminal 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 or CU without parsing it. In the following embodiments, if the transmission of such signaling between the DU and the terminal is involved, then the sending or receiving of the signaling by the DU includes this scenario. For example, the signaling of the RRC or PDCP layer will eventually be processed into physical layer data and sent to the terminal, or converted from the received physical layer data. Under this architecture, the signaling of the RRC layer or PDCP layer can also be considered to be sent by the DU, or sent by the DU and the radio frequency device.

[0082] It can be understood that the embodiments of the present application do not limit the number of access network devices and the number of terminals included in the communication system. In addition, in addition to the access network devices and terminals, the above-mentioned communication system may also include other devices or network elements, such as core network devices, relay devices, etc., which are not limited by the embodiments of the present application.

[0083] The following first explains the relevant technical features involved in the embodiments of the present application. It should be noted that these explanations are intended to make the embodiments of the present application easier to understand and should not be regarded as limiting the scope of protection claimed by the present application.

[0084] (1) Cell switching

[0085] Cell handover can be divided into two types, one of which is cell handover based on layer 1 / layer 2, which can be called layer 1 / layer 2 handover or layer 1 / layer 2 triggered mobility (L1 / L2 triggered mobility, LTM), and the other is cell handover based on layer 3, which can be called layer 3 handover (L3 handover). Among them, layer 1 can refer to the physical layer, layer 2 can refer to any one or more layers of the MAC layer, RLC layer, PDCP layer, and SDAP layer, and layer 3 can refer to the RRC layer. Since layer 1 and layer 2 are located at a lower level of the protocol stack than the RRC layer (layer 3), layer 1 / layer 2 handover can also be called low-layer handover, or bottom layer handover, or lower-layer handover. This application does not limit the name of the specific handover technology.

[0086] For Layer 3 handover, in a CU-DU separation architecture, the CU receives the terminal's measurement results (which are forwarded to the CU by the DU) and determines whether to initiate a handover based on these results. If so, the handover command is sent to the DU, which then sends it to the terminal. This process involves communication interaction between the CU and DU (i.e., interaction over the F1 interface), and the maximum transmission latency of the F1 interface is approximately 3ms to 10ms, which results in a certain handover latency.

[0087] The switching decision for Layer 1 / Layer 2 switching is sent from the CU to the DU. That is, the DU determines whether to initiate a switch (LTM cell switch) based on the terminal's measurement results and sends the switching command message directly to the terminal, which can effectively reduce F1 interactions and shorten switching latency.

[0088] (2) Cell switching scenarios

[0089] When a terminal switches between different cells, there may be multiple specific switching scenarios. For example, the switching scenarios may be divided according to the positional relationship between the source cell and the target cell.

[0090] Among them, when the access network device adopts a CU-DU separation architecture (for example, the access network device includes a CU and multiple DUs, the multiple DUs are centrally controlled by one CU, and each of the multiple DUs may include one or more cells), the positional relationship between the source cell and the target cell may refer to whether the source cell and the target cell belong to the same CU and / or the same DU. Among them, "DU includes one or more cells" can also be described as "DU manages or controls one or more cells", or "one or more cells of DU", or "one or more cells belong to DU". Three possible switching scenarios are described here, namely scenarios 1 to 3.

[0091] Scenario 1: A terminal switches from one cell in a DU to another cell in the same DU. In other words, the source and target cells belong to the same DU. The cell handover corresponding to Scenario 1 is called intra-DU handover.

[0092] Scenario 2: A terminal switches from a cell in DU1 controlled by a CU to a cell in DU2 controlled by the same CU. DU1 is called the source DU, and DU2 is called the target DU. In other words, the source and target cells of the terminal belong to different DUs controlled by the same CU. The cell handover in Scenario 2 is called an inter-DU handover.

[0093] Scenario 3: The terminal switches from a cell in DU1 controlled by CU1 to a cell in DU3 controlled by CU2. In this case, CU1 is called the source CU and CU2 is called the target CU. In other words, the source and target cells of the terminal belong to different DUs controlled by different CUs. The cell handover corresponding to Scenario 2 is called inter-CU handover.

[0094] When the access network device is considered as a whole (e.g., a gNB), the location relationship between the source cell and the target cell can refer to whether the source cell and the target cell belong to the same access network device. Two possible handover scenarios are described here: Scenario 4 and Scenario 5.

[0095] Scenario 4: A terminal switches from a cell on access network device 1 to a cell on access network device 2. In this case, access network device 1 is called the source access network device, and access network device 2 is called the target access network device. In other words, the source and target cells of the terminal belong to different access network devices. The cell handover in Scenario 4 is called inter-gNB handover.

[0096] Scenario 5: A terminal switches from one cell of an access network device to another cell of the same access network device. In other words, the source and target cells of the terminal belong to the same access network device. The cell handover corresponding to Scenario 5 is called intra-gNB handover.

[0097] The communication method provided in the embodiments of the present application can be applied to any of the above scenarios.

[0098] (3) Downlink synchronization

[0099] Downlink timing is used for downlink synchronization between the terminal and the access network equipment. Downlink timing can be a cell-level parameter, with each cell having a corresponding downlink timing parameter. Downlink timing is defined as the time (in terms of time) that the first path of the corresponding downlink frame used by the terminal to determine downlink timing is received from the reference cell at the UE antenna. For details, refer to existing protocols.

[0100] Taking the 5G communication system as an example, uplink and downlink transmission can use time slots as the basic time unit, that is, data is transmitted once in each time slot. The start time of the time slot of the access network device is fixed, and the uplink and downlink time slots are aligned. For downlink transmission, the downlink signal sent by the access network device propagates through the air to the terminal side, and there will be propagation delay. For example, the signal propagation delay between DU1 belonging to cell A and the terminal is Tp1, and the signal propagation delay between DU2 belonging to cell B and the terminal is Tp2. Therefore, taking cell A as an example, the terminal can determine the downlink timing of cell A by receiving the reference signal of cell A.

[0101] Here, the downlink timing difference involved below is explained: As shown in Figure 3A, downlink reference signal 1 sent by DU1 at the downlink timeslot boundary of cell A arrives at the terminal after Tp1. The terminal determines downlink timeslot boundary 1 based on the received downlink reference signal 1. There is a time difference of Tp1 between the downlink timeslot boundary of cell A and the downlink timeslot boundary 1 determined by the terminal. Downlink reference signal 2 sent by DU2 at the downlink timeslot boundary of cell B arrives at the terminal after Tp2. The terminal determines downlink timeslot boundary 2 based on the received downlink reference signal 2. There is a time difference of Tp2 between the downlink timeslot boundary of cell B and the downlink timeslot boundary 2 determined by the terminal. Therefore, the time difference between the downlink timeslot boundary determined by the terminal for cell A (e.g., downlink timeslot boundary 1) and the downlink timeslot boundary determined by the terminal for cell B (e.g., downlink timeslot boundary 2) is the downlink timing difference between cells A and B. It is understood that the downlink timeslot boundary can also be replaced by a downlink frame boundary.

[0102] (4) Uplink synchronization

[0103] Timing advance (TA) is used for uplink synchronization between the terminal and the access network equipment. TA can be a cell-level parameter, with each cell having a corresponding TA. For example, the terminal can use the TA of cell A to send uplink data to the DU belonging to cell A.

[0104] For cell handover, the terminal may obtain the TA of the target cell by sending a random access preamble. Two possible methods, namely, method 1 and method 2, are described below.

[0105] Method 1: Random access-based method

[0106] Before performing a cell handover (or before receiving a handover command), the terminal can send a random access preamble to a candidate DU on one or more candidate cells. For example, if one or more candidate cells include cell A, the terminal can send a random access preamble to DU1, which belongs to cell A, on cell A. DU1 can then measure the TA of cell A and send the TA of cell A to the terminal's target DU (such as DU2). Subsequently, if DU2 decides to handover the terminal to cell A, it can send the TA of cell A to the terminal via a handover command. The terminal can then obtain the TA of cell A and, after handing over to cell A, communicate based on the TA of cell A.

[0107] Method 2: Based on the terminal measuring the downlink reference signal

[0108] The terminal can determine the downlink timing of cell A by measuring the downlink reference signal of cell A, and determine the downlink timing of cell B by measuring the downlink reference signal of cell B; furthermore, the terminal can determine the TA of cell A or cell B based on the downlink timing difference between cell A and cell B.

[0109] Taking cell A as the target cell, if the downlink time slot boundaries of cell A and cell B (cell B may be the source cell of the terminal) are synchronized, as shown in FIG3B , then the TA of cell A can be determined based on the downlink timing difference by the following formula 1: TA_targetcell=TA_sourcecell+2*(Tnew-Told)……Formula 1

[0110] Among them, TA_targetcell represents the TA of cell A, TA_sourcecell represents the TA of cell B, Tnew-Told is the downlink timing difference between cell A and cell B, Tnew is the downlink timing of cell A, and Told is the downlink timing of cell B.

[0111] The above formula 1 can also be transformed into: TA_targetcell=TA_sourcecell-2*(Told-Tnew)

[0112] If the downlink time slot boundaries of cell A and cell B (cell B may be the source cell of the terminal) are not synchronized, the TA of cell A can be determined based on the downlink timing difference by the following formula 2: TA_targetcell=TA_sourcecell+2*(Tnew-Told)+offset……Formula 2

[0113] Here, offset represents the downlink time slot boundary deviation between cell A and cell B.

[0114] In addition, whether the downlink time slot boundaries of cell A and cell B are synchronized, and the downlink time slot boundary deviation between cell A and cell B may be indicated to the terminal by the access network device, and the specific implementation is not limited.

[0115] Carrier aggregation is a technology that combines radio channel resources within or across frequency bands to increase user data rates and reduce latency. In carrier aggregation scenarios, a terminal can have multiple serving cells. One of these cells is the primary cell (PCell), and the others are secondary cells (SCells). The terminal can simultaneously transmit data on both the PCell and the SCell. For example, the terminal can send uplink data on both the PCell and the SCell simultaneously; or receive downlink data on both the PCell and the SCell simultaneously.

[0116] In a cell switching scenario, after the terminal switches to the target cell (the target cell is the primary cell of carrier aggregation), it needs to synchronize with the secondary cell first. Only after synchronization is completed can the terminal perform data transmission on the secondary cell. Since the terminal cannot perform data transmission on the secondary cell during the synchronization process between the terminal and the secondary cell, after the terminal switches to the target cell, it first performs data transmission on the primary cell (at a low rate at this time). After the terminal and the secondary cell complete synchronization, the terminal can perform data transmission on both the primary cell and the secondary cell at the same time (at a high rate at this time). With this method, in a cell switching scenario, data transmission cannot be performed quickly through carrier aggregation, resulting in a decrease in throughput and an inability to guarantee high-speed data transmission.

[0117] Based on this, an embodiment of the present application provides a communication method for achieving early synchronization for carrier aggregation in a cell handover scenario, thereby ensuring high-speed data transmission. The communication method provided in the embodiment of the present application involves at least one network device and a terminal. The network device involved in the embodiment of the present application is described below in conjunction with some of the handover scenarios described above:

[0118] (1) In the same DU handover (scenario 1), the network devices involved in the embodiments of the present application may include a first network device and a second network device. The second network device is a CU, the first network device is a DU managed by the CU, and the source cell and candidate cell of the terminal both belong to the DU.

[0119] (2) In cross-DU switching (scenario 2), the network devices involved in the embodiment of the present application may include a first network device and a second network device, and optionally, a third network device. The second network device may be a CU, the first network device may be a first DU managed by the CU (i.e., the source DU of the terminal), and the third network device may be a second DU managed by the CU (i.e., the candidate DU of the terminal). The first DU, the second DU, and the CU may belong to the same access network device (such as a gNB). In the embodiment of the present application, if the terminal switches to a cell managed by a candidate DU, the candidate DU may also be referred to as a target DU, and other similarities (such as candidate cells and candidate access network devices) may be handled with reference to the above.

[0120] (3) In cross-CU switching (scenario 3), the network devices involved in the embodiments of the present application may include a first network device and a second network device, and optionally, a third network device and / or a fourth network device. The second network device may be the first CU, the first network device may be the first DU managed by the first CU (i.e., the source DU of the terminal), the third network device may be the second CU, and the fourth network device may be the second DU managed by the second CU (i.e., the candidate DU of the terminal).

[0121] (4) In cross-site handover (Scenario 4), the network devices involved in the embodiments of the present application may include a first network device and a second network device. The first network device may be a first access network device (source access network device), and the second network device may be a second access network device (candidate access network device).

[0122] (5) In the same-site handover (scenario 5), the network device involved in the embodiment of the present application may include an access network device, and the source access network device and the candidate access network device of the terminal are both the access network device.

[0123] The communication method provided by the embodiments of the present application is described in detail below in conjunction with Examples 1 to 3. Unless otherwise specified, "terminal" may refer to the terminal itself or a component in the terminal, such as a chip or a chip system; "network device" may refer to the network device itself or a component in the network device, such as a chip or a chip system.

[0124] Example 1

[0125] FIG4 is a flow chart of the communication method according to the first embodiment of the present application. As shown in FIG4 , the method includes:

[0126] S401: A second network device sends a first message to a first network device, where the first message is used to request the first network device to perform early synchronization for carrier aggregation; accordingly, the first network device receives the first message.

[0127] Here, the primary cell of carrier aggregation is the first cell, the secondary cell of carrier aggregation includes the second cell, and the secondary cell of carrier aggregation may also include other cells (such as a third cell). In the embodiment of this application, "the primary cell of carrier aggregation is the first cell, and the secondary cell of carrier aggregation is the second cell" is used as an example for description. The primary cell and secondary cell of carrier aggregation may belong to the same network device (such as the same DU or the same access network device).

[0128] The above-mentioned first network device can be the source DU or source access network device of the terminal. When the first network device is the source DU of the terminal, the second network device can be the CU for managing the first network device (such as scenario 1, scenario 2 and scenario 3). The primary cell and secondary cell of the above-mentioned carrier aggregation can belong to the candidate DU. In scenario 2 and scenario 3, the candidate DU and the source DU are different DUs. In this case, the second network device obtains the configuration information of the carrier aggregation and sends the configuration information of the carrier aggregation to the first network device, and then the first network device can forward the configuration information of the carrier aggregation to the terminal. When the first network device is the source access network device of the terminal, the second network device can be the candidate access network device of the terminal (such as scenario 4). The primary cell and secondary cell of the above-mentioned carrier aggregation can belong to the candidate access network device. The candidate access network device and the source access network device are different access network devices. In this case, the second network device sends the configuration information of the carrier aggregation to the first network device (for example, the configuration information of the carrier aggregation can be carried in the first message), and then the first network device sends the configuration information of the carrier aggregation to the terminal. The configuration information of the carrier aggregation includes the configuration information of each cell of the carrier aggregation. For details, please refer to the subsequent embodiments. It should be understood that if the source access network device of the terminal and the candidate access network device are the same access network device (such as scenario 5), there is no need to execute S401.

[0129] Exemplarily, the first message includes candidate carrier aggregation information (i.e., candidate CA information), and the candidate CA information is used to request the first network device to perform early synchronization for carrier aggregation. For example, the candidate CA information includes information 1 and / or information 2. Information 1 is used to indicate that the primary cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation is the second cell. Information 2 includes the identifiers of one or more secondary cells of the carrier aggregation (such as the identifier of the second cell), and the identifiers of the one or more secondary cells are used to request the first network device to perform early synchronization for the one or more secondary cells; that is, when there are multiple secondary cells of the carrier aggregation, information 2 can specifically indicate which secondary cells are requested for early synchronization.

[0130] It can be understood that: (1) when the candidate CA information includes information 1 but does not include information 2, the candidate CA information implicitly requests the first network device to perform early synchronization for all secondary cells of the carrier aggregation. When the candidate CA information includes information 1 and information 2, the candidate CA information explicitly requests the first network device to perform early synchronization for one or some secondary cells of the carrier aggregation. In the embodiment of the present application, it is not limited whether the first network device performs early synchronization for the primary cell. Under normal circumstances, the first network device can perform early synchronization for the primary cell by default. Therefore, no additional information is required in the first message to request the first network device to perform early synchronization for the primary cell.

[0131] (2) The above description takes the candidate CA information corresponding to a carrier aggregation scenario (i.e., the primary cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation is the second cell) as an example. In other embodiments, the first message may include multiple candidate CA information, such as first candidate CA information and second candidate CA information. The carrier aggregation scenario corresponding to the first candidate CA information is "the primary cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation is the second cell", and the carrier aggregation scenario corresponding to the second candidate CA information is "the primary cell of the carrier aggregation is the second cell, and the secondary cell of the carrier aggregation is the first cell". For details, please refer to the above. Exemplarily, when the first message includes multiple candidate CA information, the network device to which the carrier aggregation cell corresponding to each candidate CA information in the multiple candidate CA information belongs is different from the first network device.

[0132] S402. The first network device sends first indication information to the terminal according to the first message, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell; accordingly, the terminal receives the first indication information.

[0133] Optionally, the first network device may further send a second message to the second network device, where the second message is used to indicate a request to accept the first message.

[0134] Here, the early synchronization may include early uplink synchronization and / or early downlink synchronization.

[0135] (1) When early synchronization includes early uplink synchronization, the first indication information is used to instruct the terminal to perform early uplink synchronization with the second cell. In this case, the first indication information can be carried in downlink control information (DCI) or other possible messages.

[0136] As a possible implementation, the first indication information is used to instruct the terminal to send a random access signal on the second cell (that is, the first indication information is used to instruct early uplink synchronization based on random access). For example, the first indication information is a physical downlink control channel (PDCCH) order (PDCCH order). Accordingly, after receiving the first indication information, the terminal can send a random access signal on the second cell, and the random access signal is used to determine the TA of the second cell. After the DU or access network device to which the second cell belongs determines the TA of the second cell based on the random access signal, it can send the TA of the second cell to the first network device, and then the first network device sends the TA of the second cell to the terminal (for example, the first network device sends the TA of the second cell to the terminal through the handover command message below).

[0137] As another possible implementation, the first indication information is used to instruct the terminal to perform early uplink synchronization based on measuring a downlink reference signal. Accordingly, after receiving the first indication information, the terminal can determine the TA of the second cell according to Formula 1 or Formula 2.

[0138] (2) When early synchronization includes early downlink synchronization, the first indication information is used to instruct the terminal to perform early downlink synchronization with the second cell. In this case, the first indication information can be carried in a MAC layer message or other possible messages, and the MAC layer message is, for example, a MAC control element (CE). Specifically, the first indication information is used to activate the transmission configuration indication state (TCI state) of the second cell, for example, the first indication information includes the activated TCI state information of the second cell. Accordingly, the terminal can receive the downlink reference signal of the second cell according to the activated TCI state of the second cell, and further determine (or track) the downlink timing of the second cell.

[0139] (3) When the early synchronization includes early uplink synchronization and early downlink synchronization, the first indication information may include indication information 1 and indication information 2. Indication information 1 is used to instruct the terminal to perform early uplink synchronization with the second cell, and indication information 2 is used to instruct the terminal to perform early downlink synchronization with the second cell. For details, refer to the above description. Alternatively, the first network device may also send an indication information (i.e., the first indication information) to the terminal, where the indication information is used to instruct the terminal to perform early uplink synchronization and early downlink synchronization with the second cell.

[0140] There are various scenarios for the above-mentioned "the first network device sending the first indication information to the terminal based on the first message." For example, the first network device can obtain the terminal's location information. Based on the terminal's location information, if it determines that the terminal is likely to move into the coverage area of ​​the first cell, it can determine whether the secondary cell corresponding to the first cell (i.e., the second cell) requires early synchronization based on the candidate CA information in the first message. If the first network device determines that the second cell requires early synchronization, it sends the first indication information to the terminal.

[0141] Optionally, after the first network device sends the first indication information to the terminal, if it is determined to switch the terminal to the first cell, a switching command message is sent to the terminal, and the switching command message is used to instruct the terminal's primary cell to switch to the first cell; accordingly, the terminal switches to the first cell according to the switching command message. The above-mentioned early uplink synchronization may refer to the uplink synchronization of the terminal before receiving the switching command message, and the above-mentioned early downlink synchronization may refer to the downlink synchronization of the terminal before receiving the switching command message. Since the terminal synchronizes with the second cell before receiving the switching command, after the terminal switches to the first cell, it can simultaneously transmit data on the first cell and the second cell in a carrier aggregation manner.

[0142] Optionally, after the first network device sends a handover command message to the terminal, the first network device or the terminal may send at least one of the following ①②③④ to the DU or access network device to which the first cell belongs (that is, the DU or access network device to which the second cell belongs). Two possible implementations are described below in conjunction with Implementation 1 and Implementation 2.

[0143] Implementation method 1: After the first network device sends a handover command message to the terminal, if the first network device is the source DU of the terminal, the first network device may send at least one of the following ①②③④ to the DU belonging to the first cell through the CU (such as the first CU and the second CU), such as through the LTM cell change notification message, to send at least one of the following ①②③④ to the DU belonging to the first cell. If the first network device is the source access network device, the first network device may send at least one of the following ①②③④ to the access network device (i.e., the candidate access network device) belonging to the first cell.

[0144] Implementation method 2: After the first network device sends a switching command message to the terminal, the terminal can switch to the first cell according to the switching command message, and then the terminal can send at least one of the following ①②③④ to the DU or access network device to which the first cell belongs on the first cell, such as sending at least one of the following ①②③④ to the DU or access network device to which the first cell belongs through a MAC layer message.

[0145] ① Second indication information: the second indication information is used to indicate that early synchronization for carrier aggregation has been performed.

[0146] Exemplarily, the second indication information may include an identifier of the second cell, and the identifier of the second cell is used to indicate that early synchronization has been performed for the second cell. That is, the identifier of the cell included in the second indication information may be used to specifically indicate which cells have been early synchronized.

[0147] Exemplarily, if early synchronization includes early uplink synchronization and early downlink synchronization, the second indication information may include indication information 3 and indication information 4, indication information 3 is used to indicate that early uplink synchronization of carrier aggregation has been performed, and indication information 4 is used to indicate that early downlink synchronization of carrier aggregation has been performed.

[0148] For implementation method 1, "early synchronization for carrier aggregation has been performed" can be replaced with "early synchronization for carrier aggregation has been completed" or "early synchronization for carrier aggregation has been initiated." As can be seen from the above description, the first network device sends the first indication information to the terminal, instructing the terminal to perform early synchronization with the second cell. The first network device may not know whether the terminal has completed early synchronization with the second cell. Therefore, when the first network device sends the first indication information to the terminal, the first network device may deem that "early synchronization for carrier aggregation has been performed" and send the second indication information to the DU or access network device to which the first cell belongs.

[0149] Optionally, if the first network device does not send the first indication information to the terminal, the first network device may send third indication information to the DU or access network device to which the first cell belongs, where the third indication information is used to indicate that "early synchronization for carrier aggregation is not performed." Exemplarily, the third indication information may include an identifier of the second cell, where the identifier of the second cell is used to indicate that early synchronization for the second cell is not performed.

[0150] For implementation method 2, "early synchronization for carrier aggregation has been performed" can be replaced with "early synchronization for carrier aggregation has been completed." As can be seen from the above description, the terminal can perform early synchronization with the second cell based on the first indication information. Therefore, when the terminal completes early synchronization with the second cell, the terminal can send the second indication information to the DU or access network device to which the first cell belongs.

[0151] Optionally, if the terminal has not completed early synchronization with the second cell, the terminal may send third indication information to the DU or access network device to which the first cell belongs, where the third indication information is used to indicate that "early synchronization for carrier aggregation has not been performed." Exemplarily, the third indication information may include an identifier of the second cell, where the identifier of the second cell is used to indicate that early synchronization for the second cell has not been performed.

[0152] Accordingly, the DU or access network device to which the first cell belongs can be informed, based on the second indication information, that early synchronization (such as uplink synchronization and / or downlink synchronization) has been performed for the second cell, and can then allocate resources to the terminal on the second cell and communicate with the terminal through the allocated resources. If the DU or access network device to which the first cell belongs determines that early synchronization for the second cell has not been performed, it is necessary to instruct the terminal to synchronize with the second cell.

[0153] ②Activated TCI status information of the second cell

[0154] The activated TCI state information of the second cell is used to indicate the activated TCI state of the second cell. For example, the activated TCI state information of the second cell includes an identifier of the activated TCI state of the second cell. The activated TCI state of the second cell is the activated TCI state of the second cell indicated by the first indication information.

[0155] Since the first network device indicates the activated TCI status of the second cell to the terminal, the first network device or the terminal can send the activated TCI status information of the second cell to the DU or access network device to which the second cell belongs, so that subsequent terminals can communicate with the DU or access network device to which the first cell belongs based on the activated TCI status of the second cell to improve communication efficiency.

[0156] It is understandable that the above ② may also include the activated TCI status information of the first cell. For details, please refer to the description of the activated TCI status information of the second cell.

[0157] ③CSI of the second cell

[0158] After the first network device sends the first indication information to the terminal, the terminal may measure the downlink reference signal of the second cell based on the first indication information and determine the downlink timing of the second cell. Further, after the terminal determines the downlink timing of the second cell, the terminal may obtain the CSI of the second cell by measuring the downlink reference signal of the second cell and send the CSI of the second cell to the first network device. Furthermore, the first network device may send the CSI of the second cell to the DU or access network device to which the second cell belongs. Alternatively, after measuring and obtaining the CSI of the second cell, the terminal may save the CSI of the second cell and, after switching to the first cell, send the CSI of the second cell to the DU or access network device to which the first cell belongs.

[0159] Accordingly, the DU or access network device to which the first cell belongs can allocate resources to the terminal in the second cell based on the CSI of the second cell, and perform data transmission with the terminal on the allocated resources. Since the CSI of the second cell is measured in advance by the terminal (for example, measured before the terminal switches to the first cell), after the terminal switches to the first cell, the DU or access network device to which the first cell belongs can allocate resources to the terminal based on the CSI of the second cell measured in advance, facilitating rapid data transmission in the second cell.

[0160] ④ Synchronization mode information: The synchronization mode information is used to indicate whether the advance synchronization mode is based on random access or based on the terminal measuring the downlink reference signal.

[0161] For example, if the method of early synchronization is indicated to the terminal by the first network device, the first network device or the terminal may send the synchronization method information to the DU or access network device to which the first cell belongs. If the method of early synchronization is flexibly determined by the terminal itself, the terminal may send the synchronization method information to the DU or access network device to which the first cell belongs. Optionally, the synchronization method information may be included in the second indication information. In addition, in other embodiments, if the method of early synchronization is predefined by the protocol, the first network device or the terminal may not need to send the synchronization method information to the DU or access network device to which the first cell belongs.

[0162] Generally speaking, the accuracy of synchronization based on random access is higher, while the accuracy of synchronization based on the terminal measuring the downlink reference signal is relatively low. Therefore, after the DU or access network device to which the first cell belongs receives the synchronization mode information, it can decide whether to instruct the terminal to adjust the TA of the second cell based on the synchronization mode information. For example, if the synchronization mode information indicates that the advance synchronization method is based on the terminal measuring the downlink reference signal, the DU or access network device to which the first cell belongs can subsequently instruct the terminal to adjust the TA of the second cell to improve the synchronization accuracy.

[0163] Regarding Implementation Methods 1 and 2 above, it is understood that if ①②③④ are sent via Implementation Method 1 or Implementation Method 2, then ①②③④ can be carried in the same message or in different messages. Implementation Methods 1 and 2 can be implemented separately or in combination, for example, sending part of ①②③④ via Implementation Method 1 and sending the other part of ①②③④ via Implementation Method 2.

[0164] With the above method, since early synchronization for carrier aggregation can be performed in a cell switching scenario, the terminal can quickly transmit data through carrier aggregation after switching to the target cell, thereby ensuring high-speed data transmission.

[0165] Based on the above embodiment 1, two possible implementation processes are described below in combination with embodiment 2 and embodiment 3.

[0166] Example 2

[0167] In the second embodiment, inter-DU handover (scenario 2) is taken as an example for description.

[0168] FIG5 is a flow chart of the communication method according to the second embodiment of the present application. As shown in FIG5 , the method includes:

[0169] S501: The CU sends a message 1 to the second DU, where the message 1 is used to request configuration information of carrier aggregation.

[0170] Exemplarily, Message 1 may include primary cell information and secondary cell information. The primary cell information includes an identifier of a first cell, used to request configuration of the first cell as a primary cell for carrier aggregation; the secondary cell information includes an identifier of a second cell, used to request configuration of the second cell as a secondary cell for carrier aggregation. The first cell and the second cell are different cells, and both belong to a second DU.

[0171] In the embodiment of the present application, Message 1 is also used to request early synchronization for carrier aggregation. Message 1 may implicitly request early synchronization for carrier aggregation; alternatively, Message 1 may explicitly request early synchronization for carrier aggregation. For example, the secondary cell information in Message 1 may also include request information corresponding to the secondary cell (e.g., the second cell), and the request information corresponding to the second cell is used to request early synchronization for the second cell.

[0172] In addition, there may be multiple triggering factors for the CU to send Message 1 to the second DU. For example, the terminal sends a measurement report to the first DU, and the measurement report includes the measurement results of Layer 3, which may specifically include the measurement results of neighboring cells. The neighboring cell refers to the cell to which the terminal may switch after moving. Furthermore, the first DU sends the measurement report to the CU, for example, the first DU sends an uplink (UL) RRC message to the CU, and the UL RRC message includes the measurement report; accordingly, the CU can decide whether to initiate LTM configuration based on the measurement report. If the CU decides to initiate LTM configuration, it can send Message 1 to the second DU.

[0173] S502 , the second DU sends a message 2 to the CU, where the message 2 includes configuration information of carrier aggregation; accordingly, the CU receives the message 2 .

[0174] Exemplarily, the configuration information of carrier aggregation may include the configuration information of the primary cell (first cell) and the configuration information of the secondary cell (second cell). The configuration information of the first cell may include the lower layer RRC configuration, transmission configuration indicator (TCI) state configuration and random access channel (RACH) configuration and reference signal (RS) configuration corresponding to the first cell as the primary cell. The random access channel configuration may include the random access preamble configured for the terminal, the time-frequency resources for carrying the random access preamble, etc. The configuration information of the second cell may include the lower layer RRC configuration corresponding to the second cell as the secondary cell, and optionally, also includes TCI state configuration, random access channel configuration and reference signal configuration. The above-mentioned "lower layer" may include layer 1 and / or layer 2.

[0175] Optionally, message 2 also includes an early synchronization acceptance indication, which is used to instruct the second DU to accept early synchronization for carrier aggregation. Exemplarily, the early synchronization acceptance indication may include the identifiers of one or more secondary cells of the carrier aggregation, and the identifiers of the one or more secondary cells are used to instruct the second DU to accept early synchronization for the one or more secondary cells. That is, when there are multiple secondary cells of the carrier aggregation, the second DU can accept early synchronization of all secondary cells of the carrier aggregation, or can also accept early synchronization of some secondary cells of the carrier aggregation. Therefore, by carrying the identifiers of the secondary cells in the early synchronization acceptance indication, it can be indicated which secondary cells the second DU specifically accepts early synchronization.

[0176] In other embodiments, the message 2 may not include an indication of accepting the early synchronization. In this case, the configuration information of the carrier aggregation may be used to implicitly indicate that the third network device accepts the early synchronization for the carrier aggregation.

[0177] The above message 1 may be a UE context setup request message, and the message 2 may be a UE context modification response message.

[0178] It can be understood that the F1AP configuration process of carrier aggregation can be completed through the above S501 and S502. The above S501 and S502 take a carrier aggregation scenario (i.e., the main cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation is the second cell) as an example. In other embodiments, S501 and S502 can be repeatedly executed for multiple carrier aggregation scenarios so that the CU obtains the configuration information corresponding to different carrier aggregation scenarios. For example, if carrier aggregation scenario 1 is "the main cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation is the second cell", then for carrier aggregation scenario 1, by executing the above S501 and S502, the CU can obtain the configuration information corresponding to carrier aggregation scenario 1; if carrier aggregation scenario 2 is "the main cell of the carrier aggregation is the second cell, and the secondary cell of the carrier aggregation is the first cell", then for carrier aggregation scenario 2, by executing the above S501 and S502, the CU can obtain the configuration information corresponding to carrier aggregation scenario 2.

[0179] Taking the second cell as an example, for carrier aggregation scenario 1, the second cell is a secondary cell, and the configuration information of the second cell obtained by the CU includes the corresponding lower-layer RRC configuration when the second cell is a secondary cell, and optionally, also includes the TCI state configuration, random access channel configuration, and reference signal configuration of the second cell; for carrier aggregation scenario 2, the second cell is a primary cell, and the configuration information of the second cell obtained by the CU includes the corresponding lower-layer RRC configuration when the second cell is a primary cell, as well as the TCI state configuration, random access channel configuration, and reference signal configuration of the second cell. Among them, the TCI state configuration, random access channel configuration, and reference signal configuration of the second cell in carrier aggregation scenario 1 are the same as the TCI state configuration, random access channel configuration, and reference signal configuration of the second cell in carrier aggregation scenario 2. Therefore, the configuration information of the second cell in carrier aggregation scenario 1 may not include the TCI state configuration, random access channel configuration, and reference signal configuration of the second cell.

[0180] S503: The CU sends a message 3 (or referred to as a first message) to the first DU. The message 3 is used to request the first DU to perform early synchronization for carrier aggregation.

[0181] Here, message 3 may include candidate CA information, for details refer to the description in embodiment 1. Optionally, message 3 also includes the TCI state configuration of the first cell and the RACH resource configuration of the first cell, as well as the TCI state configuration of the second cell and the RACH resource configuration of the second cell.

[0182] S504 , the first DU sends message 4 (or referred to as the second message) to the CU. Message 4 is used to indicate acceptance of the request of message 3 .

[0183] Exemplarily, message 4 may include the channel state information (CSI) resource configuration of the source cell, where the CSI resource configuration is used by the terminal to send lower layer measurement results (such as layer 1 / layer 2 measurement results) of the candidate cell (such as the first cell) in the source cell.

[0184] The above message 3 may be a UE context modification request message, and the message 4 may be a UE context modification response message.

[0185] Optionally, the CU may also send a UE context modification request message to the second DU, where the UE context modification request message may include: identification information of the source cell and the RS configuration of the source cell. Accordingly, the third network device sends a UE context modification response message to the first DU, where the UE context modification response message may include: a CSI resource configuration generated by the third network device, where the CSI resource configuration is used by the terminal to send the CSI of the candidate cell on the first cell; for example, when the terminal switches to the first cell, the first cell becomes the source cell, and the source cell becomes the candidate cell.

[0186] S505 , the CU sends an RRC reconfiguration message to the terminal, where the RRC reconfiguration message includes configuration information of carrier aggregation; accordingly, the terminal receives the RRC reconfiguration message.

[0187] For example, there are multiple ways for the CU to send carrier aggregation configuration information to the terminal. For example, the CU sends a downlink (DL) RRC message to the first DU, where the DL RRC message includes an RRC reconfiguration message; accordingly, after receiving the DL RRC message, the first DU sends the RRC reconfiguration message to the terminal.

[0188] Optionally, for implementation mode 2 in embodiment 1, the RRC reconfiguration message includes fourth indication information, and the fourth indication information is used to instruct the terminal to report at least one of ①②③④. Alternatively, the RRC reconfiguration message does not include the fourth indication information, and the terminal reports at least one of ①②③④ by default.

[0189] In addition, the RRC reconfiguration message may also include the CSI configuration of the source cell, the CSI resource configuration of the first cell, etc.

[0190] S506 , the terminal sends an RRC reconfiguration completion message to the CU; correspondingly, the CU receives the RRC reconfiguration completion message.

[0191] Here, after receiving the RRC reconfiguration message, the terminal may send an RRC reconfiguration completion message to the first DU, and the first DU may forward the RRC reconfiguration completion message to the CU.

[0192] S507, the first DU sends first indication information to the terminal, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell; accordingly, the terminal receives the first indication information.

[0193] S508: The terminal performs early synchronization with the second cell according to the first indication information.

[0194] For example, taking early uplink synchronization as an example, based on a random access method, after receiving the first indication information, the terminal can send a random access signal to the second DU on the second cell according to the random access channel configuration of the second cell. Furthermore, the second DU determines the TA (referred to as TA1) of the second cell based on the random access signal, and sends TA1 and the random access information corresponding to TA1 to the first DU through the CU. The random access information corresponding to TA1 is used to indicate which random access preamble code the second DU receives on which time-frequency resource in which cell. For example, the random access information corresponding to TA1 includes a cell identifier (such as the identifier of the second cell), time-frequency resource information, and a random access preamble code index.

[0195] Accordingly, after the first DU receives TA1 and the random access information corresponding to TA1, it can determine that the cell corresponding to TA1 is the second cell based on the cell identifier included in the random access information, and the terminal corresponding to TA1 can be determined based on the time-frequency resource information and random access preamble code index included in the random access information. Then, the first DU can save TA1 and the correspondence between TA1 and the cell and terminal.

[0196] For another example, in a method where the terminal measures a downlink reference signal, after receiving the first indication information, the terminal may determine the TA of the second cell according to Formula 1 or Formula 2 and save the information.

[0197] S509: The terminal sends a measurement report to the first DU, where the measurement report includes lower layer measurement results of multiple candidate cells.

[0198] For example, the terminal may measure the RSs of multiple candidate cells according to the RS configurations of the multiple candidate cells to obtain lower layer measurement results of the multiple candidate cells, and send the lower layer measurement results of the multiple candidate cells to the first DU according to the CSI resource configuration of the source cell.

[0199] S510 , the first DU sends a handover command message to the terminal, where the handover command message is used to instruct the terminal to handover from a primary cell to a first cell; accordingly, the terminal hands over to the first cell according to the handover command message.

[0200] Exemplarily, if the first DU determines to switch the terminal to the first cell based on the lower layer measurement results of multiple candidate cells, a switching command message is sent to the terminal, and the switching command message includes TA1 and the identifier of the cell corresponding to TA1 (i.e., the second cell) or the identifier of the timing advance group (TAG) 1 corresponding to TA1, and TAG1 includes the second cell. Among them, the TAs of the cells with the same TAG are all TAs corresponding to the TAG. Optionally, the switching command message also includes TA2 and the identifier of the cell corresponding to TA2 (i.e., the first cell) or the identifier of TAG2 corresponding to TA2, and TAG2 includes the first cell. The way the first DU obtains TA2 can refer to the description of the first DU obtaining TA1, and will not be repeated here.

[0201] Optionally, the handover command message also includes activated TCI status information of the first cell, and the activated TCI status information of the first cell is used for the terminal to receive downlink control information in a random access-free manner.

[0202] S511 , the first DU sends an LTM cell change notification message to the CU. The LTM cell change notification message is used to indicate that a cell handover command has been initiated for the terminal. Accordingly, the CU receives the LTM cell change notification message.

[0203] Here, the LTM cell change notification message includes the identification information of the target cell. Optionally, for implementation mode 1 in embodiment 1, the LTM cell change notification message further includes at least one of ①②③④.

[0204] S512, the CU sends an LTM cell change notification message to the second DU; correspondingly, the second DU receives the LTM cell change notification message.

[0205] S513: After detecting the access of the terminal, the second DU sends a successful access message to the CU, and performs data transmission with the terminal in the carrier aggregation cell (the first cell and the second cell).

[0206] For example, the terminal accesses the second DU on the first cell through random access or random access-free mode; accordingly, the second DU can detect the access of the terminal and send downlink control information to the terminal based on the activated TCI state information of the first cell. The random access-free mode is that the terminal accesses the first cell through the physical uplink shared channel (PUSCH) based on the TA of the first cell in the handover command message, rather than accessing the first cell through the random access channel.

[0207] For example, the behavior of the second DU side may refer to the description in the first embodiment.

[0208] S514: After receiving the successful access message, the CU sends a UE context release command message to the first DU, wherein the UE context release command message is used to instruct the release of resources of the candidate cell of the source DU.

[0209] S515 : After releasing the resources of the candidate cell of the source DU according to the UE context release command message, the first DU sends a UE context release completion message to the CU.

[0210] It is understandable that the above steps are based on scenario 2 as an example, and scenarios 1 and 3 can be implemented with reference to them. In scenario 1, since the first DU and the second DU can be the same DU, there is no need to perform related operations for interaction between the first DU and the second DU; in scenario 3, the first CU manages the first DU and the second CU manages the second DU. The interaction between the first DU and the second DU in the above embodiment (for example, the first DU sends information a to the second DU) can be replaced by: the first DU sends information a to the first CU, the first CU sends information a to the second CU, and then the second CU sends information a to the second DU.

[0211] Example 3

[0212] In the third embodiment, cross-site handover (scenario 4) is taken as an example for description.

[0213] FIG6 is a flow chart of the communication method according to the third embodiment of the present application. As shown in FIG6 , the method includes:

[0214] S601 , a first access network device sends a message 5 to a second access network device, where the message 5 is used to request configuration information of carrier aggregation; accordingly, the second access network device receives the message 5 .

[0215] Here, the first access network device and the second access network device are different access network devices. The specific content of message 5 can refer to the description of message 1 in embodiment 2.

[0216] S602 , the second access network device sends message 6 (or referred to as a first message) to the first access network device, where message 6 includes configuration information of carrier aggregation; accordingly, the first access network device receives message 6 .

[0217] Here, message 6 also includes candidate CA information (or an indication of acceptance of early synchronization), for details, refer to the description in embodiment 1 or embodiment 2. The configuration information of the above-mentioned carrier aggregation can refer to the description in embodiment 2.

[0218] Exemplarily, message 5 and message 6 may be Xn messages.

[0219] S603: The first access network device sends carrier aggregation configuration information to the terminal; correspondingly, the terminal receives the carrier aggregation configuration information.

[0220] Exemplarily, the first access network device sends an RRC reconfiguration message to the terminal. The RRC reconfiguration message includes configuration information of carrier aggregation. For details, reference may be made to the description of the RRC reconfiguration message in the second embodiment.

[0221] S604: The terminal sends an RRC reconfiguration completion message to the first access network device.

[0222] S605. The first access network device sends first indication information to the terminal, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell; accordingly, the terminal receives the first indication information.

[0223] S606: The terminal performs early synchronization with the second cell according to the first indication information.

[0224] For example, taking early uplink synchronization as an example, based on a random access method, after receiving the first indication information, the terminal can send a random access signal to the second access network device on the second cell according to the random access channel configuration of the second cell. Furthermore, the second access network device determines the TA (referred to as TA1) of the second cell based on the random access signal, and sends TA1 and the random access information corresponding to TA1 to the first access network device. The random access information corresponding to TA1 is used to indicate which random access preamble code the second access network device received on which time-frequency resource in which cell. For example, the random access information corresponding to TA1 includes a cell identifier (such as the identifier of the second cell), time-frequency resource information, and a random access preamble code index.

[0225] Accordingly, after the first access network device receives TA1 and the random access information corresponding to TA1, it can determine that the cell corresponding to TA1 is the second cell based on the cell identifier included in the random access information, and can determine the terminal corresponding to TA1 based on the time-frequency resource information and random access preamble code index included in the random access information, and then the first access network device can save TA1 and the correspondence between TA1 and the cell and terminal.

[0226] For another example, in a method where the terminal measures a downlink reference signal, after receiving the first indication information, the terminal may determine the TA of the second cell according to Formula 1 or Formula 2 and save the information.

[0227] S607: The terminal sends a measurement report to the first access network device, where the measurement report includes measurement results of multiple candidate cells.

[0228] S608 , the first access network device sends a handover command message to the terminal, where the handover command message is used to instruct the terminal to handover the primary cell to the first cell; accordingly, the terminal hands over to the first cell according to the handover command message.

[0229] For example, S605 and S606 may refer to the description of S508 and S509 in the second embodiment.

[0230] S609: The first access network device sends a cell change notification message to the second access network device. The cell change notification message is used to indicate that a cell handover command has been initiated for the terminal.

[0231] S610: After detecting access of the terminal, the second access network device sends a UE context release command message to the first access network device, and performs data transmission with the terminal in the carrier aggregated cell (the first cell and the second cell).

[0232] For example, the behavior of the second access network device side may refer to the description in the first embodiment.

[0233] S611: After releasing the resources of the candidate cell of the source DU according to the UE context release command message, the first access network device sends a UE context release completion message to the second access network device.

[0234] It is understood that the above steps are based on scenario 4 as an example, and scenario 5 can be implemented accordingly. In scenario 5, since the first access network device and the second access network device can be the same access network device, there is no need to perform operations related to interaction between the first access network device and the second access network device.

[0235] With respect to the various embodiments of the present application, it can be understood that:

[0236] (1) The above embodiments mainly describe the early synchronization of the secondary cell. The early synchronization of the primary cell can be implemented similarly, or the primary cell may not perform early synchronization. The embodiments of the present application do not limit the implementation of the primary cell. In addition, the message names involved in the embodiments of the present application are only examples and are not specifically limited.

[0237] (2) The above description focuses on the differences between different implementations or different examples. Except for the differences, the different implementations or different examples can refer to each other. In addition, different implementations or different examples can be implemented partially, combined, or partially combined, etc., and the embodiments of this application will not be listed one by one.

[0238] (3) The step numbers in the flowcharts described in the above embodiments are merely examples of the execution process and do not limit the order in which the steps are executed. In the embodiments of the present application, steps that do not have a temporal dependency on each other may not be strictly executed in any particular order. Furthermore, not all of the steps shown in the flowcharts are mandatory steps. Some steps may be added or deleted based on actual needs, or only some of the steps in the flowcharts may be executed.

[0239] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of device interaction. It is understandable that, in order to implement the above functions, each device may include a hardware structure and / or software module that performs each function. Those skilled in the art should easily appreciate that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the embodiments of the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in a hardware or computer software driven hardware manner depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0240] In the embodiments of the present application, the terminal and network device can be divided into functional units according to the above method examples. For example, each functional unit can be divided according to each function, or two or more functions can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or software functional units.

[0241] In the case of adopting an integrated unit, Figure 7 shows a possible exemplary block diagram of the device involved in the embodiments of the present application. As shown in Figure 7, the device 700 may include: a processing unit 702 and a communication unit 703. The processing unit 702 is used to control and manage the actions of the device 700. The communication unit 703 is used to support the communication between the device 700 and other devices. Optionally, the communication unit 703 is also called a transceiver unit, and may include a receiving unit and / or a sending unit, which are used to perform receiving and sending operations respectively. The device 700 may also include a storage unit 701 for storing program code and / or data of the device 700.

[0242] (1) The apparatus 700 may be the first network device in the above-described embodiment. The processing unit 702 may support the apparatus 700 in executing the actions of the first network device in each of the above-described method examples. Alternatively, the processing unit 702 may primarily execute the internal actions of the first network device in the method examples, and the communication unit 703 may support communication between the apparatus 700 and other devices.

[0243] For example, in one embodiment, the communication unit 703 is used to: receive a first message from a second network device, where the first message is used to request the first network device to perform early synchronization for carrier aggregation, where the primary cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation includes the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; and according to the first message, send first indication information to the terminal, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell.

[0244] In one possible design, after sending the first indication information to the terminal, the communication unit 703 is further used to: send a switching command message to the terminal, where the switching command message is used to instruct the primary cell of the terminal to switch to the first cell.

[0245] In one possible design, the early synchronization includes uplink synchronization and / or downlink synchronization of the terminal before receiving the switching command message.

[0246] In one possible design, the first message includes identification information of the second cell, where the identification information of the second cell is used to request the first network device to perform early synchronization for the second cell.

[0247] In one possible design, the first indication information is used to activate the transmission configuration indication TCI state of the second cell, and the TCI state is used by the terminal to determine the downlink timing of the second cell.

[0248] In one possible design, the communication unit 703 is further used to: send activated TCI status information of the second cell to the second network device.

[0249] In one possible design, the first indication information is used to instruct the terminal to send a random access signal on the second cell, and the random access signal is used to determine the timing advance TA of the second cell.

[0250] In one possible design, the communication unit 703 is further used to: receive the TA of the second cell; and send a switching command message to the terminal, where the switching command message includes the TA of the second cell.

[0251] In one possible design, the switching command message also includes the TA of the first cell.

[0252] In one possible design, the communication unit 703 is further used to: send second indication information to the second network device, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

[0253] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0254] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on terminal measurement of downlink reference signals.

[0255] In one possible design, the communication unit 703 is also used to: receive the channel state information CSI of the second cell sent by the terminal, where the CSI of the second cell is determined based on the first indication information; and send the CSI of the second cell to the second network device.

[0256] (2) The apparatus 700 may be the second network device in the above-described embodiments. The processing unit 702 may support the apparatus 700 in executing the actions of the second network device in each of the above-described method examples. Alternatively, the processing unit 702 may primarily execute the internal actions of the second network device in the method examples, and the communication unit 703 may support communication between the apparatus 700 and other devices.

[0257] For example, in one embodiment, the communication unit 703 is used to: send a first message to a first network device, where the first message is used to request the first network device to perform early synchronization for carrier aggregation, where the primary cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation includes the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; and receive a second message from the first network device, where the second message is used to indicate acceptance of the request for the first message.

[0258] In one possible design, the communication unit 703 is further used to: receive second indication information from the first network device or terminal, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

[0259] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0260] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on the terminal measuring the downlink reference signal.

[0261] In one possible design, the communication unit 703 is further used to: receive the CSI of the second cell from the first network device or terminal, where the CSI of the second cell is determined before the terminal switches to the first cell.

[0262] In one possible design, the communication unit 703 is further used to: receive activated TCI status information of the second cell from the first network device or terminal.

[0263] (3) The apparatus 700 may be a terminal in the above-described embodiments. The processing unit 702 may support the apparatus 700 in executing the terminal actions in the above-described method examples. Alternatively, the processing unit 702 may primarily execute the internal actions of the terminal in the method examples, and the communication unit 703 may support communication between the apparatus 700 and other devices.

[0264] For example, in one embodiment, the communication unit 703 is used to: receive configuration information of carrier aggregation, where the main cell of the carrier aggregation is the first cell, and the secondary cell of the carrier aggregation includes the second cell; receive first indication information, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; and perform early synchronization with the second cell according to the first indication information.

[0265] In one possible design, after receiving the first indication information, the communication unit 703 is further used to: receive a switching command message, where the switching command message is used to instruct the terminal to switch to the first cell, and the switching command message includes the TA of the second cell.

[0266] In one possible design, the communication unit 703 is further used to: send second indication information, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

[0267] In one possible design, the second indication information includes identification information of the second cell, and the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

[0268] In one possible design, the second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the early synchronization mode is based on random access or based on the terminal measuring the downlink reference signal.

[0269] In one possible design, the communication unit 703 is further used to: send the CSI of the second cell, where the CSI of the second cell is determined based on the first indication information.

[0270] In one possible design, the first indication information is used to activate the transmission configuration indication TCI state of the second cell; the processing unit 702 is used to determine the downlink timing of the second cell according to the activated TCI state of the second cell.

[0271] In one possible design, the communication unit 703 is further used to: send activated TCI status information of the second cell.

[0272] In one possible design, the first indication information is used to instruct the terminal to send a random access signal on the second cell; the communication unit 703 is also used to: send a random access signal on the second cell according to the first indication information, and the random access signal is used to determine the TA of the second cell.

[0273] It should be understood that the division of units in the above device is merely a division of logical functions. In actual implementation, they can be fully or partially integrated into one physical entity, or they can be physically separated. Moreover, the units in the device can all be implemented in the form of software calling through processing elements; or they can all be implemented in the form of hardware; or some units can be implemented in the form of software calling through processing elements, and some units can be implemented in the form of hardware. For example, each unit can be a separately established processing element, or it can be integrated into a certain chip of the device. In addition, it can also be stored in the memory in the form of a program, called by a certain processing element of the device and execute the function of the unit. In addition, all or part of these units can be integrated together, or they can be implemented independently. The processing element described here can also be a processor, which can be an integrated circuit with signal processing capabilities. In the implementation process, each operation of the above method or each unit above can be implemented by the integrated logic circuit of the hardware in the processor element or in the form of software calling through the processing element.

[0274] In one example, the unit in any of the above devices may be one or more integrated circuits configured to implement the above method, such as one or more application specific integrated circuits (ASICs), one or more digital singnal processors (DSPs), one or more field programmable gate arrays (FPGAs), or a combination of at least two of these integrated circuit forms. For another example, when the unit in the device can be implemented in the form of a processing element scheduler, the processing element can be a processor, such as a general-purpose central processing unit (CPU), or other processor that can call a program. For another example, these units can be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0275] The above-mentioned receiving unit is an interface circuit of the device, which is used to receive signals from other devices. For example, when the device is implemented as a chip, the receiving unit is the interface circuit of the chip used to receive signals from other chips or devices. The above-mentioned sending unit is an interface circuit of the device, which is used to send signals to other devices. For example, when the device is implemented as a chip, the sending unit is the interface circuit of the chip used to send signals to other chips or devices.

[0276] Referring to Figure 8, which is a schematic diagram of the structure of a network device provided in an embodiment of the present application, the network device can be applied to the communication system shown in Figure 1 to perform the functions of the network device in the above method embodiment. As shown in Figure 8, the network device 80 can be an access network device, and the network device 80 may include one or more DUs 801 and one or more CUs 802. The DU 801 may include at least one antenna 8011, at least one radio frequency unit 8012, at least one processor 8013 and at least one memory 8014. The DU 801 is mainly used for receiving and transmitting radio frequency signals, converting radio frequency signals into baseband signals, and partial baseband processing. The CU 802 may include at least one processor 8022 and at least one memory 8021.

[0277] The CU 802 is primarily used for baseband processing and controlling network devices. The DU 801 and CU 802 can be physically located together or separately, i.e., in a distributed base station. The CU 802 is the control center of the network device, also known as a processing unit, and is primarily used to perform baseband processing. For example, the CU 802 can be used to control the network device to execute the network device operation process described in the above method embodiments.

[0278] In addition, the network device 80 may optionally include one or more radio frequency units, one or more DUs, and one or more CUs. The DU may include at least one processor 8013 and at least one memory 8014, the radio frequency unit may include at least one antenna 8011 and at least one radio frequency unit 8012, and the CU may include at least one processor 8022 and at least one memory 8021.

[0279] In one example, the CU802 may be composed of one or more single boards, and the multiple single boards may jointly support a wireless access network with a single access indication (such as a 5G network), or may respectively support wireless access networks with different access standards (such as an LTE network, a 5G network, or other networks). The memory 8021 and the processor 8022 may serve one or more single boards. That is, a memory and a processor may be separately set on each single board. It is also possible that multiple single boards share the same memory and processor. In addition, necessary circuits may be provided on each single board. The DU801 may be composed of one or more single boards, and the multiple single boards may jointly support a wireless access network with a single access indication (such as a 5G network), or may respectively support wireless access networks with different access standards (such as an LTE network, a 5G network, or other networks). The memory 8014 and the processor 8013 may serve one or more single boards. That is, a memory and a processor may be separately set on each single board. It is also possible that multiple single boards share the same memory and processor. In addition, necessary circuits may be provided on each single board.

[0280] The network device shown in FIG8 is capable of implementing each process related to the network device in the above-described method embodiment. The operations and / or functions of the various modules in the network device shown in FIG8 are respectively for implementing the corresponding processes in the above-described method embodiment. For details, please refer to the description of the above-described method embodiment. To avoid repetition, detailed description is omitted here.

[0281] Refer to Figure 9, which is a structural diagram of a terminal provided in an embodiment of the present application. The terminal can be applied to the communication system shown in Figure 1 to implement the operations of the terminal in the above embodiment. As shown in Figure 9, the terminal includes: an antenna 910, a radio frequency part 920, and a signal processing part 930. The antenna 910 is connected to the radio frequency part 920. In the downlink direction, the radio frequency part 920 receives information sent by the network device through the antenna 910, and sends the information sent by the network device to the signal processing part 930 for processing. In the uplink direction, the signal processing part 930 processes the information of the terminal and sends it to the radio frequency part 920. The radio frequency part 920 processes the information of the terminal and sends it to the network device through the antenna 910.

[0282] The signal processing unit 930 may include a modem subsystem for processing data at various communication protocol layers; a central processing unit for processing the terminal operating system and application layers; and other subsystems, such as a multimedia subsystem for controlling the terminal's camera and screen display, and a peripheral subsystem for connecting to other devices. The modem subsystem may be a separate chip.

[0283] The modem subsystem may include one or more processing elements 931, such as a main control CPU and other integrated circuits. Furthermore, the modem subsystem may include a storage element 932 and an interface circuit 933. Storage element 932 is used to store data and programs. However, the program used to execute the method executed by the terminal in the above method may not be stored in storage element 932, but rather in a memory external to the modem subsystem, and loaded by the modem subsystem when in use. Interface circuit 933 is used to communicate with other subsystems.

[0284] The modem subsystem can be implemented using a chip comprising at least one processing element and an interface circuit. The processing element is configured to execute each step of any of the methods performed by the terminal, and the interface circuit is configured to communicate with other devices. In one implementation, the unit that performs each step of the method can be implemented as a processing element scheduler. For example, the terminal device includes a processing element and a storage element, and the processing element invokes a program stored in the storage element to execute the method performed by the terminal in the above method embodiments. The storage element can be a storage element located on the same chip as the processing element, i.e., an on-chip storage element.

[0285] In another implementation, the program for executing the method executed by the terminal in the above method can be stored in a memory element on a different chip from the processing element, i.e., an off-chip memory element. In this case, the processing element calls or loads the program from the off-chip memory element to the on-chip memory element to call and execute the method executed by the terminal in the above method embodiment.

[0286] In another implementation, the unit implementing each step of the above method in the terminal may be configured as one or more processing elements, which are provided in the modem subsystem. The processing elements may be integrated circuits, such as one or more ASICs, one or more DSPs, one or more FPGAs, or a combination of these integrated circuits. These integrated circuits may be integrated together to form a chip.

[0287] The units that implement the various steps of the above method in the terminal can be integrated together and implemented in the form of a SOC chip, which is used to implement the above method. The chip can integrate at least one processing element and a storage element, and the processing element can call the program stored in the storage element to implement the above terminal execution method; alternatively, the chip can integrate at least one integrated circuit to implement the above terminal execution method; or, a combination of the above implementation methods can be used, with the functions of some units implemented by the processing element calling the program, and the functions of some units implemented by the integrated circuit.

[0288] As can be seen, the above-mentioned terminal device may include at least one processing element and an interface circuit, wherein the at least one processing element is used to execute any of the terminal-executed methods provided in the above method embodiments. The processing element may execute some or all of the steps executed by the terminal in a first manner: by calling a program stored in a storage element; or in a second manner: by combining hardware integrated logic circuits in the processor element with instructions to execute some or all of the steps executed by the terminal. Of course, the first and second manners may also be combined to execute some or all of the steps executed by the terminal.

[0289] The processing element here can be implemented by a processor as described above, and the functions of the processing element can be the same as those of the processing unit described in Figure 7. For example, the processing element can be a general-purpose processor, such as a CPU, or one or more integrated circuits configured to implement the above method, such as one or more ASICs, or one or more microprocessors (DSPs), or one or more FPGAs, or a combination of at least two of these integrated circuit forms. The storage element can be implemented by a memory, and the functions of the storage element can be the same as those of the storage unit described in Figure 7. The storage element can be a single memory or a collective term for multiple memories.

[0290] The terminal shown in FIG9 is capable of implementing the various processes involved in the terminal in the above-described method embodiment. The operations and / or functions of the various modules in the terminal shown in FIG9 are respectively for implementing the corresponding processes in the above-described method embodiment. For details, please refer to the description of the above-described method embodiment. To avoid repetition, detailed description is omitted here.

[0291] The terms "system" and "network" in the embodiments of the present application can be used interchangeably. "At least one" refers to one or more, and "plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of A, B or C" includes A, B, C, AB, AC, BC or ABC, and "at least one of A, B and C" can also be understood to include A, B, C, AB, AC, BC or ABC. And, unless otherwise specified, the ordinal numbers such as "first" and "second" mentioned in the embodiments of the present application are used to distinguish multiple objects and are not used to limit the order, timing, priority or importance of multiple objects.

[0292] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, optical storage, etc.) that contain computer-usable program code.

[0293] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the present application. It should be understood that each flow and / or box in the flow chart and / or block diagram, as well as the combination of the flow chart and / or box in the flow chart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more flow charts and / or one or more boxes in the block diagram.

[0294] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0295] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0296] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A communication method, characterized in that: The method is applied to a first network device, and the method includes: receiving a first message from a second network device, where the first message is used to request the first network device to perform early synchronization for carrier aggregation, where a primary cell of the carrier aggregation is a first cell, and a secondary cell of the carrier aggregation includes a second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; According to the first message, first indication information is sent to the terminal, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell.

2. The method according to claim 1, characterized in that After sending the first indication information to the terminal, the method further includes: Sending a handover command message to the terminal, where the handover command message is used to instruct a primary cell of the terminal to switch to the first cell; The advance synchronization includes uplink synchronization and / or downlink synchronization of the terminal before receiving the switching command message.

3. The method according to claim 1 or 2, characterized in that: The first message includes identification information of the second cell, where the identification information of the second cell is used to request the first network device to perform early synchronization for the second cell.

4. The method according to any one of claims 1 to 3, characterized in that The first indication information is used to activate the transmission configuration indication TCI state of the second cell, and the TCI state is used by the terminal to determine the downlink timing of the second cell.

5. The method according to claim 4, characterized in that The method further comprises: Send activated TCI status information of the second cell to the second network device.

6. The method according to any one of claims 1 to 5, characterized in that The first indication information is used to instruct the terminal to send a random access signal on the second cell, and the random access signal is used to determine a timing advance TA of the second cell.

7. The method according to claim 6, characterized in that The method further comprises: receiving a TA of the second cell; A handover command message is sent to the terminal, where the handover command message includes the TA of the second cell.

8. The method according to any one of claims 1 to 7, characterized in that The method further comprises: Sending second indication information to the second network device, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

9. The method according to claim 8, characterized in that The second indication information includes identification information of the second cell, where the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

10. The method according to claim 8 or 9, characterized in that: The second indication information includes synchronization mode information, and the synchronization mode information is used to indicate that the advance synchronization mode is: a random access-based mode or a terminal-based mode of measuring a downlink reference signal.

11. The method according to any one of claims 1 to 10, characterized in that The method further comprises: receiving channel state information CSI of the second cell sent by the terminal, where the CSI of the second cell is determined according to the first indication information; Send the CSI of the second cell to the second network device.

12. A communication method, characterized in that: The method is applied to a second network device, and the method includes: Sending a first message to a first network device, where the first message is used to request the first network device to perform early synchronization for carrier aggregation, where a primary cell of the carrier aggregation is a first cell, and a secondary cell of the carrier aggregation includes a second cell, and the early synchronization includes early uplink synchronization and / or early downlink synchronization; A second message is received from the first network device, where the second message is used to indicate a request to accept the first message.

13. The method according to claim 12, characterized in that The method further comprises: Second indication information is received from the first network device or the terminal, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

14. The method according to claim 13, characterized in that The second indication information includes identification information of the second cell, where the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

15. The method according to claim 13 or 14, characterized in that The second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the advance synchronization mode is: a random access-based mode or a terminal-based mode of measuring a downlink reference signal.

16. The method according to any one of claims 12 to 15, characterized in that The method further comprises: Receive CSI of the second cell from the first network device or the terminal, where the CSI of the second cell is obtained when the terminal switches to the The first cell is measured previously.

17. The method according to any one of claims 12 to 16, characterized in that The method further comprises: Receive activated TCI status information of the second cell from the first network device or terminal.

18. A communication method, characterized in that: The method is applied to a terminal, and the method includes: receiving configuration information of carrier aggregation, where a primary cell of the carrier aggregation is a first cell, and a secondary cell of the carrier aggregation includes a second cell; receiving first indication information, where the first indication information is used to instruct the terminal to perform early synchronization with the second cell, where the early synchronization includes early uplink synchronization and / or early downlink synchronization; Perform early synchronization with the second cell according to the first indication information.

19. The method according to claim 18, characterized in that After receiving the first indication information, the method further includes: A handover command message is received, where the handover command message is used to instruct the terminal to handover to the first cell, and the handover command message includes a TA of the second cell.

20. The method according to claim 18 or 19, characterized in that The method further comprises: Second indication information is sent, where the second indication information is used to indicate that early synchronization for the carrier aggregation has been performed.

21. The method according to claim 20, characterized in that The second indication information includes identification information of the second cell, where the identification information of the second cell is used to indicate that early synchronization has been performed for the second cell.

22. The method according to claim 20 or 21, characterized in that The second indication information includes synchronization mode information, and the synchronization mode information is used to indicate whether the advance synchronization mode is: a random access-based mode or a terminal-based mode of measuring a downlink reference signal.

23. The method according to any one of claims 18 to 22, characterized in that The method further comprises: Send CSI of the second cell, where the CSI of the second cell is determined based on the first indication information.

24. The method according to any one of claims 18 to 23, characterized in that The first indication information is used to activate a transmission configuration indication TCI state of the second cell; According to the first indication information, early synchronization is performed with the second cell, including: determining the downlink timing of the second cell according to the activated TCI state of the second cell.

25. The method according to claim 24, characterized in that The method further comprises: Send activated TCI status information of the second cell.

26. A communication device, characterized in that: Comprising means for executing the method as claimed in any one of claims 1 to 25.

27. A communication device, characterized in that: It includes a processor, which is coupled to a memory, and a computer program is stored in the memory; the processor is used to call the computer program in the memory, so that the communication device executes the method as claimed in any one of claims 1 to 25.

28. A communication system, characterized in that: The communication system includes a first network device, a second network device and a terminal; wherein the first network device is used to execute the method described in any one of claims 1 to 11, the second network device is used to execute the method described in any one of claims 12 to 17, and the terminal is used to execute the method described in any one of claims 18 to 25.

29. A computer-readable storage medium, characterized in that: The storage medium stores a computer program or instruction, and when the computer program or instruction is executed by a computer, the method as claimed in any one of claims 1 to 25 is implemented.

30. A computer program product, characterized in that When a computer reads and executes the computer program product, the computer is enabled to execute the method according to any one of claims 1 to 25.

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