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 receiving a first message, the first message comprising first TA information of a first cell; determining that the first TA information corresponds to a first TAG among a plurality of TAGs, the plurality of TAGs corresponding to the first cell; and sending a second message to a terminal, the second message comprising identifier information of a target cell to which the terminal is to be handed over, the first TA information, and identifier information of the first TAG corresponding to the first TA information, and the target cell being the first cell. By using the method, after determining that the first TA information corresponds to the first TAG, the first network device sends the first TA information and the identifier information of the first TAG to the terminal, so that the terminal can determine that the first TA information corresponds to the first TAG, thereby enabling the terminal to quickly perform effective data transmission on the target cell, and improving the data transmission efficiency.

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 November 30, 2023, with application number 202311637510.5 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] Currently, multiple input and multiple output (MIMO) technology has been introduced into communication systems to improve throughput. MIMO technology refers to the use of multiple transmit antennas and multiple receive antennas at the transmitter and receiver, respectively, creating multiple independent channels between the transmitter and receiver. Building on this foundation, fifth-generation (5G) communication systems have introduced MIMO transmission technology based on multiple transmission and reception points (TRPs). A TRP can be understood as a physical transmission and reception point. The coverage of a cell can be provided by the combined coverage of multiple TRPs, ensuring full coverage.

[0005] However, after the introduction of multi-TRP transmission technology, how to ensure that the terminal can quickly and effectively transmit data on the target cell in the cell switching scenario still requires further research. Summary of the Invention

[0006] The present application provides a communication method and apparatus for enabling a terminal to obtain the correspondence between the TA and TAG of a target cell in a cell switching scenario, thereby facilitating the terminal to quickly and effectively transmit data on the target cell and improving the efficiency of data transmission.

[0007] 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, which includes first timing advance TA information of a first cell; determines that the first TA information corresponds to a first TAG in multiple timing advance groups TAG, and the multiple TAGs correspond to the first cell; sends a second message to the terminal, which includes identification information of a target cell for switching of the terminal, the first TA information, and identification information of the first TAG corresponding to the first TA information, and the target cell is the first cell.

[0008] Using the above method, after the first network device determines that the first TA information corresponds to the first TAG, it sends the first TA information and the identification information of the first TAG to the terminal, so that the terminal can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0009] In one possible design, the first message also includes first information corresponding to the first TA information; the method also includes: receiving a third message, the third message being used to indicate that the first TAG corresponds to the first information; determining that the first TA information corresponds to the first TAG among multiple TAGs, including: determining that the first TA information corresponds to the first TAG based on the first message and the third message.

[0010] In one possible design, determining that the first TA information corresponds to the first TAG based on the first message and the third message includes: determining that the first TA information corresponds to the first TAG based on the correspondence between the first TA information and the first information, and the correspondence between the first TAG and the first information.

[0011] In one possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; wherein the first TRP corresponds to the first cell.

[0012] In one possible design, the method further includes: sending first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0013] In this way, by sending the first indication information, the second network device can determine, based on the first indication information, that the terminal has acquired the TA corresponding to the first TAG, thereby facilitating subsequent scheduling of the terminal to perform data transmission of the first TAG.

[0014] In one possible design, the first message also includes the second TA information of the first cell; the method also includes: determining that the second TA information corresponds to the second TAG among the multiple TAGs; the second message also includes the second TA information and the identification information of the second TAG corresponding to the second TA information.

[0015] In this way, the first network device sends the second TA information and the identification information of the second TAG to the terminal, so that the terminal can obtain the TA corresponding to the second TAG, which facilitates subsequent rapid data transmission of the second TAG.

[0016] In one possible design, the method further includes: sending second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0017] In the second 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 a second message, and the second message includes identification information of the target cell for the terminal's switching, first TA information and identification information of a first TAG, where the first TAG is one of multiple TAGs, and the multiple TAGs correspond to the target cell; according to the second message, it is determined that the first TA information corresponds to the first TAG, and the TA indicated by the first TA information is used to access the target cell.

[0018] In one possible design, the method further includes: upon receiving the second message, starting a timer corresponding to the first TAG; wherein, during the running of the timer, the terminal is uplink synchronized with the target cell.

[0019] In one possible design, the method also includes: receiving downlink control information on the target cell, the downlink control information is used to indicate resources, and the resources are uplink resources or downlink resources; when the downlink control information or the resources indicated by the downlink control correspond to the first TAG, determining that the switching is completed.

[0020] In one possible design, the method further includes: sending first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0021] In one possible design, the second message also includes second TA information and identification information of the second TAG; the method also includes: determining, based on the second message, that the second TA information corresponds to the second TAG.

[0022] In one possible design, the method further includes: sending second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0023] In a third 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 third message, and the third message is used to indicate that the first TAG in multiple TAGs corresponds to the first information, and the multiple TAGs correspond to the first cell; sends a first message, and the first message includes first TA information and the first information corresponding to the first TA information; wherein the first message and the third message are used to determine that the first TA information corresponds to the first TAG; and determine that the terminal has obtained the TA corresponding to the first TAG.

[0024] In one possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; wherein the first TRP corresponds to the first cell.

[0025] In one possible design, the method further includes: receiving request information, where the request information is used to request random access configuration corresponding to the multiple TAGs.

[0026] In one possible design, determining that the terminal has obtained the TA corresponding to the first TAG includes: receiving first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0027] In one possible design, the third message is also used to indicate that the second TAG among the multiple TAGs corresponds to the second information, and the first message also includes the second TA information and the second information corresponding to the second TA information; wherein, the first message and the third message are also used to determine that the second TA information corresponds to the second TAG; the method also includes: receiving second indication information, the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0028] It can be understood that the communication method provided in the second aspect or the third aspect corresponds to the first aspect, and the beneficial effects of the relevant technical features in the second aspect or the third aspect can be referred to the description of the first aspect and will not be repeated here.

[0029] In a fourth 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 a fourth message, and the fourth message is used to indicate that the random access corresponds to the first TAG, and the first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell; according to the random access, the first TA information is obtained; according to the fourth message, it is determined that the first TA information corresponds to the first TAG.

[0030] Using the above method, the second network device indicates to the terminal that the random access corresponds to the first TAG, so that after the terminal obtains the first TA information according to the random access, it can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0031] In one possible design, obtaining the first TA according to the random access includes: receiving a second message, the second message including identification information of the target cell for switching of the terminal and the first TA information, the target cell being the first cell; the method also includes: when the second message is received, starting the timer corresponding to the first TAG, and during the operation of the timer, the terminal is uplink synchronized with the target cell.

[0032] In one possible design, the method also includes: using the TA indicated by the first TA information to access the target cell of the handover, the target cell being the first cell; receiving downlink control information on the first cell, the downlink control information being used to indicate resources, the resources being uplink resources or downlink resources; and determining that the handover is completed when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG.

[0033] In one possible design, the method further includes: sending first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0034] In a fifth 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 fourth message, and the fourth message is used to indicate that the random access corresponds to the first TAG, and the first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell; it is determined that the terminal has obtained the TA corresponding to the first TAG according to the random access.

[0035] In one possible design, determining that the terminal has obtained the TA corresponding to the first TAG according to the random access includes: receiving first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0036] In one possible design, the method further includes: receiving request information, where the request information is used to request random access configuration corresponding to the multiple TAGs.

[0037] It can be understood that the communication method provided in the fifth aspect corresponds to the fourth aspect, and the beneficial effects of the relevant technical features in the fifth aspect can be referred to the description of the fourth aspect and will not be repeated here.

[0038] In the sixth 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 a fifth message, and the fifth message is used to indicate that the first TA measurement corresponds to the first TAG, and the first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell; according to the first TA measurement, the first TA is obtained; according to the fifth message, it is determined that the first TA corresponds to the first TAG.

[0039] Using the above method, the second network device indicates to the terminal that the first TA measurement corresponds to the first TAG, so that after the terminal obtains the first TA information based on the first TA measurement, it can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0040] In one possible design, the method also includes: receiving a second message, the second message including identification information of a target cell for switching of the terminal, the target cell being the first cell; upon receiving the second message and obtaining the first TA based on the first TA measurement, starting a timer corresponding to the first TAG, and during the operation of the timer, the terminal is uplink synchronized with the target cell.

[0041] In one possible design, the method also includes: using the first TA to access the target cell of the switching, the target cell being the first cell; receiving downlink control information on the first cell, the downlink control information being used to indicate resources, the resources being uplink resources or downlink resources; and determining that the switching is completed when the downlink control information or the resources indicated by the downlink control information corresponds to the first TAG.

[0042] In one possible design, the first TA measurement corresponds to the first TAG, including: the first reference signal of the first cell corresponds to the first TAG, and the first reference signal is used for the first TA measurement.

[0043] In one possible design, the method further includes: sending first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0044] In one possible design, the fourth message is also used to indicate that the second TA measurement corresponds to the second TAG, and the second TAG is one of the multiple TAGs; according to the second TA measurement, the second TA is obtained; according to the fourth message, it is determined that the second TA corresponds to the second TAG.

[0045] In one possible design, the method further includes: sending second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0046] In one possible design, the second TA measurement corresponds to the second TAG, including: the second reference signal of the first cell corresponds to the second TAG, and the second reference signal is used for the second TA measurement.

[0047] In one possible design, the fifth message is also used to indicate a measurement identifier corresponding to the first reference signal; obtaining a first TA based on the first TA measurement includes: receiving a measurement identifier corresponding to a third reference signal of the second cell; when the measurement identifier corresponding to the first reference signal and the measurement identifier corresponding to the third reference signal are the same, determining the first TA based on the first reference signal, the third reference signal and the TA of the second cell.

[0048] In the seventh 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 fifth message, and the fifth message is used to indicate that the first TA measurement corresponds to the first TAG, and the first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell; it is determined that the terminal has obtained the TA corresponding to the first TAG based on the first TA measurement.

[0049] In one possible design, determining that the terminal has obtained the TA corresponding to the first TAG based on the first TA measurement includes: receiving first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0050] In one possible design, the method further includes: receiving request information, where the request information is used to request TA measurement configuration corresponding to the multiple TAGs.

[0051] In one possible design, the first TA measurement corresponds to the first TAG, including: the first reference signal of the first cell corresponds to the first TAG, and the first reference signal is used for the first TA measurement.

[0052] In one possible design, the fourth message is also used to indicate that the second TA measurement corresponds to the second TAG, and the second TAG is one of the multiple TAGs.

[0053] In one possible design, the method further includes: receiving second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0054] In one possible design, the second TA measurement corresponds to the second TAG, including: the second reference signal of the first cell corresponds to the second TAG, and the second reference signal is used for the second TA measurement.

[0055] It can be understood that the communication method provided in the seventh aspect corresponds to the sixth aspect, and the beneficial effects of the relevant technical features in the seventh aspect can be referred to the description of the sixth aspect and will not be repeated here.

[0056] In an eighth aspect, the present application provides a communication device, which has the function of implementing any one of the first to seventh aspects above. For example, the communication device includes a module or unit or means corresponding to the operation involved in any one of the first to seventh aspects above. The function or unit or means can be implemented by software, or by hardware, or the corresponding software can be implemented by hardware.

[0057] 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; 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 any of the first to seventh aspects above.

[0058] 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 any of the first to seventh aspects. 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 seventh aspects.

[0059] 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 any of the first to seventh aspects described above. The processor may 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 seventh aspects described above.

[0060] 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 seventh aspects above.

[0061] It can be understood that in the eighth 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.

[0062] In the ninth 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 third aspect, and the terminal is used to execute the method described in the second aspect.

[0063] Alternatively, the communication system may include a second network device and a terminal; wherein the second network device is used to execute the method described in the fifth aspect above, and the terminal is used to execute the method described in the fourth aspect above.

[0064] Alternatively, the communication system may include a second network device and a terminal; wherein the second network device is used to execute the method described in the seventh aspect above, and the terminal is used to execute the method described in the sixth aspect above.

[0065] In the tenth aspect, the present application provides a computer-readable storage medium, which stores computer-readable instructions. When a computer reads and executes the computer-readable instructions, the computer executes the method in any possible design of the first to seventh aspects above.

[0066] Exemplarily, a computer-readable storage medium can be any available medium that can be accessed by a computer. By way of example and not limitation, a computer-readable medium can include a non-transitory computer-readable medium, a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a CD-ROM or other optical disk storage, a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer.

[0067] In an eleventh 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 seventh aspects above.

[0068] In the twelfth aspect, the present application provides a chip (or chip system), which includes a processor, and the processor is coupled to a memory, and is used to read and execute a software program stored in the memory to implement the method in any possible design of the first to seventh aspects above. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] FIG1 is a schematic diagram of a communication system applicable to an embodiment of the present application;

[0070] FIG2A is a schematic diagram of a CU-DU separation architecture provided in an embodiment of the present application;

[0071] FIG2B is a schematic diagram of another CU-DU separation architecture provided in an embodiment of the present application;

[0072] FIG3A is a schematic diagram of a downlink timing difference provided in an embodiment of the present application;

[0073] FIG3B is a schematic diagram of timing advance provided in an embodiment of the present application;

[0074] FIG4A is a schematic diagram of a multi-TRP transmission technology provided in an embodiment of the present application;

[0075] FIG4B is another schematic diagram of a multi-TRP transmission technology provided in an embodiment of the present application;

[0076] FIG5 is a flow chart of the communication method according to the first embodiment of the present application;

[0077] FIG6 is a flow chart of the communication method according to the second embodiment of the present application;

[0078] FIG7 is a flow chart of the communication method according to the third embodiment of the present application;

[0079] FIG8 is a flow chart of the communication method according to the fourth embodiment of the present application;

[0080] FIG9 is a flow chart of the communication method according to the fifth embodiment of the present application;

[0081] FIG10 is a flow chart of a communication method according to a sixth embodiment of the present application;

[0082] FIG11 is a possible exemplary block diagram of a device involved in an embodiment of the present application;

[0083] FIG12 is a schematic diagram of the structure of a network device provided in an embodiment of the present application;

[0084] FIG13 is a schematic structural diagram of a terminal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] (1) Terminal

[0091] 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.

[0092] 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.

[0093] (2) Access network equipment

[0094] 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.

[0095] 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.

[0096] (3) Communication between terminals and access network equipment

[0097] 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).

[0098] 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.

[0099] 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.

[0100] (4) CU-DU separation architecture

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] The following first explains the relevant terms 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.

[0107] (1) Cell switching

[0108] 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.

[0109] 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.

[0110] 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.

[0111] (2) Cell switching scenarios

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] The communication method provided in the embodiments of the present application can be applied to any of the above scenarios.

[0121] (3) Downlink synchronization

[0122] 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.

[0123] 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.

[0124] 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.

[0125] (4) Uplink synchronization

[0126] Timing advance (TA) is used for uplink synchronization between the terminal and the access network equipment. When the terminal obtains the TA of cell A, it indicates that the terminal is uplink synchronized with cell A. After obtaining the TA of cell A, the terminal can use the TA of cell A to send uplink data to the DU belonging to cell A.

[0127] 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.

[0128] Method 1: Random access-based method

[0129] 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.

[0130] Method 2: Based on TA measurement or terminal measurement of downlink reference signals

[0131] 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.

[0132] 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 , the TA of cell A can be determined based on the downlink timing difference using the following formula 1:

[0133] TA_targetcell=TA_sourcecell+2*(Tnew—Told)...Formula 1

[0134] 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.

[0135] The above formula 1 can also be transformed into:

[0136] TA_targetcell=TA_sourcecell—2*(Told—Tnew)

[0137] 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 using the following formula 2:

[0138] TA_targetcell=TA_sourcecell+2*(Tnew—Told)+offset...Formula 2

[0139] Here, offset represents the downlink time slot boundary deviation between cell A and cell B.

[0140] 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.

[0141] (5) Multi-TRP transmission technology

[0142] Multi-TRP transmission technology means that multiple TRPs provide services for the same terminal, thereby improving the terminal's data transmission efficiency. Among them, these multiple TRPs can belong to the same cell under the same base station; each of these multiple TRPs has a corresponding data channel, and the terminal can transmit data in the same cell through the data channels of different TRPs. Among them, the data channel can include a physical uplink shared channel (PUSCH) and / or a physical downlink shared channel (PDSCH).

[0143] Refer to Figures 4A and 4B, which are two possible implementation examples of multi-TRP transmission technology. Among them, the method illustrated in Figure 4A is based on multiple downlink control information (DCI) methods, and the DCI is carried on the physical downlink control channel (PDCCH), that is, the two TRPs each transmit 1 DCI, and each DCI schedules 1 PUSCH or PDSCH. The method illustrated in Figure 4B is based on a single DCI method, that is, only one of the two TRPs transmits DCI, and the DCI can schedule 1 PUSCH or PDSCH; taking the DCI scheduling 1 PDSCH as an example, a part of the stream / layer in the PDSCH (corresponding to part of the demodulation reference signal (DMRS) port) is transmitted by one TRP, and the other part of the stream / layer (corresponding to part of the DMRS port) is transmitted by another TRP.

[0144] After the introduction of multi-TRP transmission technology, the terminal needs to synchronize with the TRP of the cell (for example, uplink synchronization) before transmitting data on the cell. Because different TRPs in the same cell are usually deployed in different locations, the TAs corresponding to different TRPs are different, that is, the terminal needs to use different TAs to send data to different TRPs.

[0145] In a cell switching scenario, assuming that the target cells for switching include TRP1 and TRP2, after the terminal obtains the TA of the target cell through the "random access-based method" or "terminal measurement of downlink reference signal-based method" described above, since the terminal does not know whether the TA of the target cell is for TRP1 or TRP2, this may cause the terminal to fail to transmit data on the target cell (for example, the TA of the target cell obtained by the terminal is the TA for TRP1, but the terminal uses the TA to send data to TRP2, which will cause data transmission failure), that is, effective data transmission cannot be performed, affecting the efficiency of data transmission.

[0146] Based on this, the embodiments of the present application will study the relevant implementation of the multi-TRP transmission technology in the cell switching scenario. For example, the embodiments of the present application provide a communication method for enabling a terminal to obtain the corresponding relationship between the TA and TAG of the target cell in the cell switching scenario, so as to facilitate the terminal to quickly and effectively transmit data on the target cell and improve the efficiency of data transmission.

[0147] 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 switching scenarios described above:

[0148] (1) In the same DU handover (scenario 1), the network device involved in the embodiment of the present application includes a CU and a DU managed by the CU, and the source cell and candidate cells of the terminal both belong to the DU.

[0149] (2) In cross-DU handover (scenario 2), the network devices involved in the embodiment of the present application include a CU, a first DU managed by the CU (i.e., the source DU of the terminal), and 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 (e.g., 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. Other similarities (e.g., candidate cells, candidate access network devices) may be handled similarly.

[0150] (3) In cross-CU switching (scenario 3), the network device involved in the embodiment of the present application includes a first CU, a first DU managed by the first CU (i.e., the source DU of the terminal), a second CU, and a second DU managed by the second CU (i.e., the candidate DU of the terminal).

[0151] (4) In cross-site handover (scenario 4), the network devices involved in the embodiments of the present application may include a first access network device (source access network device) and a second access network device (candidate access network device).

[0152] (5) In the same-site handover (scenario 5), the network device involved in the embodiment of the present application is an access network device (such as g-NB), and the source access network device and candidate access network device of the terminal are both the access network device.

[0153] 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.

[0154] Example 1

[0155] In the first embodiment, the interaction between the first network device, the second network device and the terminal is taken as an example for description.

[0156] Among them, for scenario 1: the first network device and the second network device can be the same DU. In this case, the relevant operations for the interaction between the first network device and the second network device may not be performed. For scenario 2: the first network device can be the first DU (i.e., the source DU), the second network device can be the second DU (i.e., the candidate DU), and the first network device and the second network device communicate via the CU, i.e., first DU->CU->second DU, or second DU->CU->first DU. For transit communication, the information transmitted between different nodes is the same, and the message names carrying this information can be the same or different, without limitation. For example, the specific implementation of "the second network device sends a third message to the first network device" is: the second network device sends a third message a to the CU, and after the CU receives the third message a, it sends a third message b to the first network device. The third message a and the third message b carry the same information, and the message names of the third message a and the third message b can be the same or different. The same is true for the first network device sending the corresponding message to the second network device, i.e., transiting through the CU. For scenario 3: the first network device can be the first DU managed by the first CU, the second network device can be the second DU managed by the second CU, and the first network device and the second network device communicate through the first CU and the second CU, that is, first DU->first CU->second CU->second DU, or second DU->second CU->first CU->first DU. For scenario 4: the first network device can be the first access network device, the second network device can be the second access network device, and the first access network device and the second access network device can communicate through the Xn interface. For scenario 5: the first network device and the second network device can be the same access network device. In this case, the relevant operations for the interaction between the first network device and the second network device may not be performed.

[0157] FIG5 is a flow chart of the communication method according to the first embodiment of the present application. As shown in FIG5 , the method includes:

[0158] S501: A second network device sends a third message to a first network device, where the third message is used to indicate that a first TAG among multiple TAGs corresponds to first information. Accordingly, the first network device receives the third message.

[0159] Here, multiple TAGs (that is, N TAGs) correspond to the same cell, that is, the first cell. The first cell is a candidate target cell for the terminal and belongs to the second network device; the source cell of the terminal belongs to the first network device. Multiple TAGs can be allocated by the second network device to the terminal for the first cell, and the multiple TAGs correspond one-to-one with the multiple TRPs corresponding to the first cell. For example, taking the first cell as an example, the first cell corresponds to M TRPs, and the first cell corresponds to N TAGs (that is, the second network device allocates N TAGs to the terminal for the first cell). The N TAGs correspond one-to-one with N TRPs out of the M TRPs, where M and N are both integers greater than 1, and M is greater than or equal to N.

[0160] In one possible implementation, the multiple TAGs include a first TAG and a second TAG. For example, the first TAG corresponds to a first TRP, and the second TAG corresponds to a second TRP. The first TAG and the second TAG are different, the first TRP and the second TRP are different, and the first TRP and the second TRP correspond to the first cell. Optionally, the third message is further used to indicate that the second TAG corresponds to the second information.

[0161] Among them, the first information is used to indicate at least one of the following: a first TRP; a first synchronization signal block (SSB); a first random access resource; a first TAG. The first information can uniquely identify the first TAG from the network side (for example, a second network device). Similar to the first information, the second information is used to indicate at least one of the following: a second TRP; identification information of a second SSB; a second random access resource; a second TAG. The second information can uniquely identify the second TAG from the network side (for example, a second network device). The following describes three possible examples of the first information in combination with Examples 1 to 3, and the second information can be processed with reference to them.

[0162] Example 1: The first information includes identification information of the first TRP. For example, the identification information of the first TRP may be newly introduced information used to uniquely identify the first TRP. The identification information of the first TRP may be allocated by the second network device.

[0163] This example can be applicable to scenarios where the SSBs corresponding to the first TRP and other TRPs (such as the second TRP) are the same, and the random access resources corresponding to the first TRP and other TRPs (such as the second TRP) are the same. For example, as shown in Table 1, the first TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resource 1 and random access resource 2, and SSB2 corresponds to random access resource 3 and random access resource 4; the second TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resource 1 and random access resource 2, and SSB2 corresponds to random access resource 3 and random access resource 4. A random access resource illustrated in the embodiment of the present application is a resource used for one random access attempt, for example, random access resource 1 is a resource used for one random access attempt, and random access resource 2 is a resource used for one random access attempt.

[0164] Table 1: Examples of SSB and random access resources corresponding to the first and second TRPs

[0165] Example 2: The first information includes identification information of the first SSB corresponding to the first TRP. For example, the first TRP corresponds to an SSB set, which includes one or more SSBs. The first SSB here may be the SSB set, or the first SSB may be one SSB in the SSB set.

[0166] This example can be applied to scenarios where the first TRP and other TRPs (such as the second TRP) correspond to different SSBs. For example, as shown in Table 2, the first TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resources 1 and random access resources 2, and SSB2 corresponds to random access resources 3 and random access resources 4; the second TRP corresponds to SSB3 and SSB4, SSB3 corresponds to random access resources 1 and random access resources 2, and SSB4 corresponds to random access resources 3 and random access resources 4.

[0167] Table 2: Examples of SSB and random access resources corresponding to the first and second TRPs

[0168] It can be understood that Table 2 is illustrated by taking the example that the random access resources corresponding to the first TRP and the second TRP are the same. In other examples, the random access resources corresponding to the first TRP and the second TRP may also be different.

[0169] Example 3: The first information includes identification information of the first random access resource corresponding to the first TRP. The identification information of the first random access resource is used to identify the first random access resource, for example, the identification information of the first random access resource is information of the first random access resource, refer to the description of information 1 below, and for example, the identification information of the first random access resource is a configuration identifier of the first random access resource.

[0170] For example, the first TRP corresponds to a random access resource set, which includes one or more random access resources, and each random access resource is used for one random access; the first random access resource here can be the random access resource set, or it can be a random access resource in the random access resource set.

[0171] This example can be applied to scenarios where the first TRP and other TRPs (such as the second TRP) correspond to different random access resources. For example, as shown in Table 3, the first TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resources 1 and random access resources 2, and SSB2 corresponds to random access resources 3 and random access resources 4; the second TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resources 5 and random access resources 6, and SSB2 corresponds to random access resources 7 and random access resources 8.

[0172] Table 3: Examples of SSB and random access resources corresponding to the first TRP and the second TRP

[0173] In addition, after receiving the third message, the first network device may store the correspondence between the first TAG and the first information, so as to facilitate subsequent determination of the TA corresponding to the first TAG.

[0174] S502 : The second network device sends a first message to the first network device, where the first message includes first TA information of a first cell. Correspondingly, the first network device receives the first message from the second network device.

[0175] For example, the second network device may first obtain the first TA information and then send the first message to the first network device. There are multiple ways for the second network device to obtain the first TA information, and one possible way is described here:

[0176] The second network device sends configuration information of the first cell to the first network device. For example, the third message includes the configuration information of the first cell, and the configuration information of the first cell includes the random access channel (RACH) configuration of the first cell. The random access channel configuration may include information of random access resources (referred to as information 1 for ease of description). For example, the random access resources include random access time-frequency resource 1 and a first preamble. Information 1 includes information indicating time-frequency resource 1 and / or identification information of the first preamble, and optionally also includes a configuration identifier of the random access resource (the configuration identifier corresponds to the identification information of the first cell).

[0177] The first network device obtains the location information of the terminal (for example, obtains the location information of the terminal based on the RSRP information of the first cell), and determines that the terminal is likely to move to the coverage of the first cell in the future based on the location information of the terminal. The first network device determines that the random access time-frequency resource 1 and the first preamble correspond to the terminal (referred to as the correspondence relationship a), and sends indication information to the terminal, which can be a physical downlink control channel (PDCCH) order (PDCCH order). The indication information is used to instruct the terminal to use the random access time-frequency resource 1 on the first cell to send a random access preamble (i.e., the first preamble); for example, the indication information includes the identification information of SSB1 and the index value of the random access time-frequency resource 1 corresponding to SSB1, and also includes the identification information of the first preamble. The random access resources corresponding to SSB1 include multiple random access time-frequency resources that appear periodically, and the index value of the random access time-frequency resource 1 is used to indicate that the random access time-frequency resource 1 is one of the multiple random access time-frequency resources.

[0178] Accordingly, after receiving the indication information, the terminal can send a random access preamble (i.e., the first preamble) on the random access time-frequency resource 1. Furthermore, the second network device determines the first TA information based on the random access preamble, and determines that the above-mentioned first information corresponds to the first TA information. Specifically, after the second network device receives the random access preamble through the first TRP, it determines the first TA information and determines that the first TA information corresponds to the first TRP. Optionally, if the second TRP of the first cell also receives the above-mentioned random access preamble, the second network device determines the second TA information and determines that the above-mentioned second information corresponds to the second TA information. Specifically, after the second network device receives the random access preamble through the second TRP, it determines the second TA information and determines that the second TA information corresponds to the second TRP. In this case, the first message also includes the second TA information.

[0179] In addition, the above-mentioned first message also includes the above-mentioned first information.

[0180] The above-mentioned first message may also include information of the random access resource corresponding to the first TA information (referred to as information 1' for ease of description), and information 1' includes the RA-RNTI corresponding to the random access time-frequency resource 1 (i.e., the first RA-RNTI), the identification information of the first cell and / or the identification information of the first preamble. For example, the second network device receives the random access preamble on the random access time-frequency resource 1 and determines the first TA information. Among them, the RA-RNTI corresponding to the random access time-frequency resource 1 (i.e., the first RA-RNTI) is determined based on the random access time-frequency resource 1. Furthermore, after receiving the first message, the first network device can determine that the first TA information corresponds to the terminal based on the first RA-RNTI, the identification information of the first preamble and the above-mentioned correspondence a.

[0181] S503: The first network device determines that the first TA information corresponds to the first TAG.

[0182] Here, there are multiple ways for the first network device to determine that the first TA information corresponds to the first TAG, and two possible implementation ways are described here.

[0183] Implementation method 1:

[0184] When the first message includes the first TA information and the first information, the first network device determines that the first TA information corresponds to the first TAG based on the first message and the third message. Specifically, the first network device determines that the first TA information corresponds to the first TAG based on the "correspondence between the first TAG and the first information" indicated in the third message and the "correspondence between the first TA information and the first information" indicated in the first message.

[0185] Optionally, the first message also includes the second TA information and the second information corresponding to the second TA information, and then the first network device determines that the second TA information corresponds to the second TAG based on the "correspondence between the second TAG and the second information" indicated by the third message and the "correspondence between the second TA information and the second information" indicated by the first message.

[0186] Implementation 2:

[0187] In the case where the first message includes the first TA information, it is assumed that the first TRP and the second TRP correspond to different SSBs, or correspond to different random access resources. After the first TRP of the first cell receives the first preamble in the randomly accessed time-frequency resource 1, the second network device can determine the first TA information of the first cell. Since the randomly accessed time-frequency resource 1 corresponds to the first TRP, even if the second TRP of the first cell receives the first preamble in the randomly accessed time-frequency resource 1, the second network device may not determine the second TA information of the first cell; even if the second network device determines the second TA information of the first cell based on the first preamble received on the randomly accessed time-frequency resource 1, it does not send the second TA information to the first network device. In other words, the first message includes the first TA information, but does not include other TA information (for example, the second TA information is not included).

[0188] In this case, the first network device determines that the first TA information corresponds to the first TAG based on the first message and the third message (and the PDCCH order). Different from the above implementation method 1, the first message does not include the first information corresponding to the first TA information.

[0189] For example, the first information is used to indicate the first SSB (such as SSB1). After receiving the first message, the first network device determines the PDCCH order of the terminal corresponding to the first TA information based on the information 1' carried by the first message; then, the first network device determines that the first TA information corresponds to the first TAG based on the identification information of SSB1 in the previously sent PDCCH order and the correspondence between the first TAG and the first SSB indicated by the third message.

[0190] For another example, when the first information is used to indicate the first random access resource (such as the random access time-frequency resource 1 and the first preamble), after the first network device receives the first message, it determines that the first TA information corresponds to the first random access resource based on the information 1' carried by the first message, and then determines that the first TA information corresponds to the first TAG based on the correspondence between the first random access resource and the first TAG indicated by the third message.

[0191] For another example, the first information is used to indicate the first TRP. After receiving the first message, the first network device determines the PDCCH order corresponding to the first TA information based on the information 1' carried by the first message; further, the first network device determines that the first TA information corresponds to the first TRP based on the identification information of SSB1 in the PDCCH order and the correspondence between the first TRP and the first SSB (the correspondence can be sent by the second network device to the first network device, such as through a third message), and determines that the first TA information corresponds to the first TAG based on the correspondence between the first TAG and the first TRP.

[0192] For the manner in which the first network device determines that the second TA information corresponds to the second TAG, refer to the above two implementation manners.

[0193] S504, the first network device sends a second message to the terminal, the second message including identification information of the target cell to be switched, the first TA information and identification information of the first TAG corresponding to the first TA information, the target cell being the first cell; accordingly, the terminal receives the second message.

[0194] Exemplarily, the second message is a handover command message, which may be transmitted via a medium access control (MAC) control element (CE). The second message includes first TA information, which is further used to instruct the terminal to access the target cell via a random access-free or RACH-less manner.

[0195] Optionally, if the first message includes the second TA information, and the first network device determines that the second TA information corresponds to the second TAG, the second message further includes the second TA information and identification information of the second TAG corresponding to the second TA information.

[0196] It should be noted that the identification information of the first TAG corresponding to the first TA information uniquely identifies the first TAG from the terminal side (the first TAG is only identified under the terminal and needs to correspond to a certain terminal), which is different from the first information (the first TAG is identified under the cell and may not need to correspond to a certain terminal).

[0197] S505: The terminal determines, according to the second message, that the first TA information corresponds to the first TAG, and uses the TA indicated by the first TA information to access the target cell.

[0198] Specifically, the terminal uses the TA indicated by the first TA information to access the target cell in a RACH-free manner.

[0199] Exemplarily, the second network device can allocate uplink resources to the terminal (for example, the uplink resources correspond to the first TAG), and then the terminal can use the TA indicated by the first TA information to send uplink information to the second network device on the uplink resources; accordingly, after the second network device receives the uplink information, it can determine that the terminal has successfully accessed the target cell.

[0200] Exemplarily, when the terminal receives the second message and the second message includes the first TA information corresponding to the first TAG, the terminal starts the timer corresponding to the first TAG (i.e., the first timing advance timer); for example, when the terminal receives the second message, the terminal starts the timer corresponding to the first TAG (i.e., the first timing advance timer). During the operation of the first timing advance timer, it can be considered that the terminal is uplink synchronized with the first TAG of the target cell. If the second message only includes the first TA information corresponding to the first TAG, only the timer corresponding to the first TAG is started, and the timer corresponding to the second TAG is not started.

[0201] Exemplarily, when the terminal receives the second message and the second message includes the second TA information corresponding to the second TAG, the terminal starts the timer corresponding to the second TAG (i.e., the second timing advance timer); for example, when the terminal receives the second message, the terminal starts the timer corresponding to the second TAG (i.e., the second timing advance timer). During the running of the second timing advance timer, it can be considered that the terminal is uplink synchronized with the second TAG of the target cell.

[0202] The duration of the first timing advance timer and / or the duration of the second timing advance timer is provided to the terminal by the second network device, for example, sent to the terminal through relay communication.

[0203] S506: The second network device determines that the terminal has acquired the TA corresponding to the first TAG.

[0204] Exemplarily, in combination with the description of S505, since the second network device receives the uplink information on the uplink resource corresponding to the first TAG, the second network device can determine that the terminal has obtained the TA corresponding to the first TAG. Alternatively, after successfully accessing the target cell, that is, the first cell, the terminal sends a first indication message to the second network device, and the first indication message is used to indicate that the terminal has obtained the TA corresponding to the first TAG. Therefore, the second network device can determine that the terminal has obtained the TA corresponding to the first TAG. Alternatively, the first network device sends the first indication message to the second network device, for example, after the first network device sends the second message to the terminal, the first indication message is sent to the second network device. Therefore, the second network device can determine that the terminal has obtained the TA corresponding to the first TAG.

[0205] Optionally, the second network device may further determine that the terminal has obtained the TA corresponding to the second TAG. For example, after accessing the first cell, the terminal sends second indication information to the second network device, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG. Alternatively, the first network device sends the second indication information to the second network device, for example, after the first network device sends the second message to the terminal, it sends the second indication information to the second network device.

[0206] The first indication information and the second indication information may be different information (for example, the first indication information includes identification information of the first TAG, and the second indication information includes identification information of the second TAG), or may be the same information (for example, one bit is used to indicate that the TA corresponding to the first TAG and the second TAG has been obtained). When the first indication information and the second indication information are different information, the first indication information and the second indication information may be carried in the same message or different messages, without specific limitation.

[0207] Optionally, the above method further includes:

[0208] S507, the second network device sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information (uplink resources or downlink resources) correspond to the first TAG, the terminal determines that the switching is completed.

[0209] Exemplarily, taking the downlink control information of the first TAG as an example, after the second network device determines that the terminal has acquired the TA corresponding to the first TAG, it schedules the terminal to transmit data for the first TAG, such as by sending downlink control information to the terminal, where the downlink control information or the resources indicated by the downlink control information correspond to the first TAG. Optionally, if the second network device determines that the terminal has not yet acquired the TA corresponding to the first TAG, it does not schedule the terminal to transmit data for the first TAG, or first instructs the terminal to perform uplink synchronization to acquire the TA corresponding to the first TAG.

[0210] Optionally, when the downlink control information or the resource indicated by the downlink control information corresponds to a non-first TAG (for example, a second TAG), the terminal cannot determine that the switching is completed (that is, the RACH-less switching is completed). It should be noted that beam 1 (that is, the transmission configuration indication state (TCI state)) corresponds to the first TAG. This correspondence is pre-configured to the terminal by the second network device. The terminal receives the downlink control information based on beam 1, and can determine that the downlink control information corresponds to the first TAG.

[0211] For example, in the scenario illustrated in FIG. 4A above, assuming that the target cell (i.e., the first cell) corresponds to the first TAG and the second TAG, the second network device may send downlink control information 1 and / or downlink control information 2 to the terminal, where downlink control information 1 corresponds to the first TAG and downlink control information 2 corresponds to the second TAG. Since the terminal accesses the target cell using the TA corresponding to the first TAG, the terminal can determine that the handover is complete only when it receives downlink control information 1; if the terminal receives downlink control information 2, it does not determine that the handover is complete.

[0212] For another example, in the scenario illustrated in FIG. 4B above, assuming that the target cell (i.e., the first cell) corresponds to the first TAG and the second TAG, the second network device may send downlink control information 3 to the terminal, where downlink control information 3 is used to indicate the resources corresponding to the first TAG or the resources corresponding to the second TAG. Since the terminal accesses the target cell using the TA corresponding to the first TAG, the terminal can determine that the handover is complete only when downlink control information 3 is used to indicate the resources corresponding to the first TAG; if downlink control information 3 is used to indicate the resources corresponding to the second TAG, the terminal does not determine that the handover is complete.

[0213] Using the above method, after the first network device determines that the first TA information corresponds to the first TAG, it sends the first TA information and the identification information of the first TAG to the terminal, so that the terminal can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0214] Example 2

[0215] In the second embodiment, based on the first embodiment, a possible implementation process will be described by taking scenario 2 as an example.

[0216] FIG6 is a flow chart of the communication method according to the second embodiment of the present application. As shown in FIG6 , the method includes:

[0217] S601: The CU sends a message 1 to the second DU, where the message 1 is used to request LTM configuration.

[0218] Exemplarily, the message 1 may include request information, where the request information is used to request random access configuration of multiple TAGs.

[0219] 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.

[0220] S602 , the second DU sends message 2 (ie, third message a) to the CU, where message 2 includes LTM configuration information of the first cell; accordingly, the CU receives message 2 .

[0221] Here, the LTM configuration information of the first cell includes the lower layer RRC configuration, reference signal configuration, transmission configuration indication state configuration and random access channel configuration of the first cell.

[0222] Furthermore, when message 1 includes request information, message 2 also includes first correspondence information of the first cell, the first correspondence information includes identification information of the first TAG, and the first information corresponding to the first TAG. Optionally, message 2 also includes one or more other correspondence information of the first cell (for example, second correspondence information of the first cell), the second correspondence information includes identification information of the second TAG, and the second information corresponding to the second TAG. The first TAG and the second TAG correspond to the first cell, the first TAG corresponds to the first TRP of the first cell, and the second TAG corresponds to the second TRP of the first cell. In this case, the first correspondence information (and the second correspondence information) are sent based on the request of the request information.

[0223] In other examples, the message 1 may not include the request information. In this case, the second DU actively sends the first correspondence information (and the second correspondence information).

[0224] The above message 1 may be a UE context setup request message, and the message 2 may be a UE context modification response message.

[0225] S603 , the CU sends message 3 (ie, the third message b) to the first DU; correspondingly, the first DU receives message 3 .

[0226] Here, message 3 may include the first correspondence information of the first cell, and optionally, the second correspondence information of the first cell. Optionally, message 3 also includes the reference signal configuration of the first cell, the TCI state configuration of the first cell, and the RACH configuration of the first cell.

[0227] S604 , the first DU sends message 4 to the CU; correspondingly, the CU receives message 4 .

[0228] 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.

[0229] The above message 3 may be a UE context modification request message, and the message 4 may be a UE context modification response message.

[0230] 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 second DU sends a UE context modification response message to the CU, where the UE context modification response message may include: a CSI resource configuration generated by the second DU, 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 above-mentioned source cell becomes the candidate cell.

[0231] S605: The CU sends an RRC reconfiguration message to the terminal; correspondingly, the terminal receives the RRC reconfiguration message.

[0232] Exemplarily, there are multiple ways for the CU to send an RRC reconfiguration message to the terminal. For example, the CU sends a downlink (DL) RRC message to the first DU, where the DL RRC message includes the RRC reconfiguration message; accordingly, after receiving the DL RRC message, the first DU sends the RRC reconfiguration message to the terminal.

[0233] Among them, the RRC reconfiguration message may include the LTM configuration information of the first cell, and optionally, other possible information, such as the CSI resource configuration of the source cell, the CSI resource configuration of the first cell, and the second DU allocating uplink resources to the terminal for the first cell (for example, the uplink resources correspond to the first TAG).

[0234] S606: The terminal sends an RRC reconfiguration completion message to the CU; correspondingly, the CU receives the RRC reconfiguration completion message.

[0235] Here, after receiving the RRC reconfiguration message, the terminal may send an uplink (UL) RRC message to the first DU, where the UL RRC message includes an RRC reconfiguration completion message; further, the first DU may forward the RRC reconfiguration completion message to the CU.

[0236] S607 , the first DU sends a PDCCH order to the terminal, where the PDCCH order is used to instruct the terminal to send a random access preamble on the first cell; accordingly, the terminal receives the PDCCH order.

[0237] S608: The terminal sends a random access preamble on the first cell according to the PDCCH order; accordingly, the second DU receives the random access preamble.

[0238] S609: The second DU determines the first TA information according to the random access preamble, and sends a message 5 (ie, a first message a) to the CU. The message 5 includes the first TA information and the first information corresponding to the first TA information.

[0239] S610, the CU sends a message 6 (ie, a first message b) to the first DU, where the message 6 includes first TA information and first information corresponding to the first TA information.

[0240] S611: The first DU determines that the first TA information corresponds to the first TAG.

[0241] It is understandable that the terminal can also perform downlink synchronization with the first cell. For example, the first DU sends a TCI state activation indication of the first cell to the terminal, and the activation indication is used to activate the TCI state of the first cell. The terminal tracks the downlink timing of the first cell based on the activation indication of the first cell.

[0242] S612: The terminal sends a measurement report to the first DU, where the measurement report includes lower layer measurement results of multiple candidate cells.

[0243] 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.

[0244] S613: The first DU sends a handover command message (ie, a second message) to the terminal. The handover command message is used to instruct the terminal to handover to the first cell.

[0245] S614: The terminal determines, according to the handover command message, that the first TA information corresponds to the first TAG, and uses the TA indicated by the first TA information to access the target cell.

[0246] 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 handover command message is sent to the terminal, where the handover command message includes the identification information of the target cell to be handed over, the first TA information, and the first information corresponding to the first TA information. Accordingly, the terminal accesses the first cell using the TA indicated by the first TA information according to the handover command message, such as accessing the first cell through the PUSCH (i.e., random access is not required).

[0247] S615 , the first DU sends an LTM cell change notification message to the CU, where 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.

[0248] Here, the LTM cell change notification message includes identification information of the target cell.

[0249] Optionally, the LTM cell change notification message further includes first indication information and / or second indication information.

[0250] S616, the CU sends an LTM cell change notification message to the second DU; correspondingly, the second DU receives the LTM cell change notification message.

[0251] S617: The second DU determines that the terminal has acquired the TA corresponding to the first TAG.

[0252] S618, the second DU sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal determines that the switching is completed.

[0253] Optionally, after the second DU detects the access of the terminal, it sends a successful access message to the CU. After receiving the successful access message, the CU sends a UE context release command message to the first DU. The UE context release command message is used to instruct the release of resources of the candidate cell of the source DU. Furthermore, after the first DU releases the resources of the candidate cell of the source DU according to the UE context release command message, it sends a UE context release complete message to the CU.

[0254] It is understood that the process illustrated in FIG6 corresponds to the process illustrated in FIG5 , and the steps of the two can be referenced to each other. For example, S602 and S603 correspond to S501 in Example 1, S609 and S610 correspond to S502 in Example 1, S611 corresponds to S503 in Example 1, S613 corresponds to S504 in Example 1, S614 corresponds to S505 in Example 1, S617 corresponds to S506 in Example 1, and S618 corresponds to S507 in Example 1.

[0255] Example 3

[0256] In the third embodiment, the interaction between the first network device, the second network device and the terminal is described as an example, wherein the first network device and the second network device can refer to the description of the first embodiment.

[0257] FIG7 is a flow chart of the communication method according to the third embodiment of the present application. As shown in FIG7 , the method includes:

[0258] S701: A second network device sends a fourth message to a terminal, where the fourth message indicates that random access corresponds to a first tag. Accordingly, the terminal receives the fourth message. In one possible implementation, there are multiple ways for the second network device to send the fourth message to the terminal. For example, in scenario 2, the second network device may send the fourth message to the terminal via relay communication.

[0259] The above S701 may also be replaced by S701'. In S701', the first network device sends a fourth message to the terminal, where the fourth message is used to indicate that the random access corresponds to the first TAG; accordingly, the terminal receives the fourth message. In one possible implementation, the fourth message is a handover command message. The second network device may indicate to the first network device that the random access corresponds to the first TAG, and the first network device may then indicate to the terminal that the random access corresponds to the first TAG via the handover command message.

[0260] The first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell (i.e., the second network device allocates multiple TAGs to the terminal for the first cell). For example, the multiple TAGs include a first TAG and a second TAG, the first TAG corresponds to a first TRP of the first cell, and the second TAG corresponds to a second TRP of the first cell. The first TRP and the second TRP correspond to different random access resources.

[0261] Exemplarily, the fourth message includes correspondence information (which may be referred to as third correspondence information), where the third correspondence information is used to indicate that the random access corresponds to the first TAG. "Random access corresponds to the first TAG" may mean that the TA field in the handover command message for the first cell corresponds to the first TAG. For example, the third correspondence information includes identification information of the first TAG, and the identification information of the first TAG is used to indicate that the random access corresponds to the first TAG.

[0262] Exemplarily, the fourth message is an RRC reconfiguration message, the RRC reconfiguration message includes the LTM configuration information of the first cell, and the above-mentioned third correspondence information may be included in the LTM configuration information of the first cell.

[0263] S702: The terminal obtains first TA information according to random access.

[0264] Exemplarily, the second network device may send a random access channel configuration of the first cell to the first network device, where the random access channel configuration may include information about a random access resource, where the random access resource is a random access resource corresponding to the first TAG (or the first TRP), for example, the random access resource includes a random access time-frequency resource 1 and a first preamble. The first network device is a network device to which the source cell of the terminal belongs.

[0265] The first network device obtains the location information of the terminal. If it is determined based on the location information of the terminal that the terminal is likely to subsequently move into the coverage of the first cell, the first network device sends indication information to the terminal. The indication information may be a PDCCH order. The indication information is used to instruct the terminal to send a random access preamble (i.e., a first preamble) using random access time-frequency resource 1 on the first cell. For example, the indication information includes identification information of SSB1 and an index value of random access time-frequency resource 1 corresponding to SSB1, as well as the first preamble.

[0266] Accordingly, after receiving the indication information, the terminal can send a random access preamble (i.e., the first preamble) on the first cell based on the use of the random access time-frequency resource 1. Furthermore, after the first TRP of the first cell receives the random access preamble, the network device to which the first cell belongs (i.e., the second network device) determines the first TA information, and the first network device sends the first TA information. It can be understood that: since the random access time-frequency resource 1 corresponds to the first TRP, even if the second TRP of the first cell receives the random access preamble on the random access time-frequency resource 1, the second network device cannot determine the second TA information of the first cell; or, even if the second network device determines the second TA information of the first cell based on the random access preamble received on the random access time-frequency resource 1, it does not send the second TA information to the first network device.

[0267] Subsequently, if the first network device determines to handover the terminal to the first cell, it sends a handover command message to the terminal. The handover command message includes identification information of the target cell to be handed over and first TA information. The first TA information is carried in the TA field of the handover command message. The target cell is the first cell, that is, the handover command message is a handover command message for the first cell. The terminal can then obtain the first TA information from the handover command message.

[0268] S703: The terminal determines, according to the fourth message, that the first TA information corresponds to the first TAG.

[0269] Here, the terminal determines, based on the third correspondence information in the fourth message, that the first TA information obtained from the TA field in the handover command message for the first cell corresponds to the first TAG.

[0270] S704: The second network device determines that the terminal has acquired the TA corresponding to the first TAG according to random access.

[0271] Optionally, the above method further includes:

[0272] S705, the second network device sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal determines that the switching is completed.

[0273] The above S704 and S705 may refer to S506 and S507 in the first embodiment.

[0274] Using the above method, the second network device indicates to the terminal that the random access corresponds to the first TAG, so that after the terminal obtains the first TA information according to the random access, it can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0275] Example 4

[0276] In the fourth embodiment, based on the third embodiment, a possible implementation process will be described by taking scenario 2 as an example.

[0277] FIG8 is a flow chart of the communication method according to the fourth embodiment of the present application. As shown in FIG8 , the method includes:

[0278] S801: The CU sends a message 1 to the second DU. The message 1 is used to request LTM configuration.

[0279] Exemplarily, the message 1 may include request information, where the request information is used to request random access configuration of multiple TAGs.

[0280] S802 , the second DU sends message 2 to the CU, where message 2 includes LTM configuration information of the first cell; accordingly, the CU receives message 2 .

[0281] Here, the LTM configuration information of the first cell includes the lower layer RRC configuration, reference signal configuration, transmission configuration indication state configuration and random access channel configuration of the first cell.

[0282] Furthermore, when message 1 includes request information, message 2 includes third correspondence information, and the third correspondence information is used to indicate that the random access corresponds to the first TAG. Alternatively, message 1 may not include request information, in which case the second DU actively sends the third correspondence information.

[0283] S803 , the CU sends message 3 to the first DU; correspondingly, the first DU receives message 3 .

[0284] Here, message 3 includes the random access channel configuration of the first cell, where the random access configuration may include information about random access resources, where the random access resources are random access resources corresponding to the first TAG (or first TRP). Optionally, message 3 also includes a reference signal configuration of the first cell, a TCI state configuration of the first cell, and a RACH configuration of the first cell.

[0285] S804 , the first DU sends message 4 to the CU; correspondingly, the CU receives message 4 .

[0286] Exemplarily, message 4 may include the channel state information 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.

[0287] The message names of messages 1 to 4 may refer to the description in the second embodiment.

[0288] S805 , the CU sends an RRC reconfiguration message to the terminal; correspondingly, the terminal receives the RRC reconfiguration message.

[0289] Here, the RRC reconfiguration message includes the LTM configuration information of the first cell and also includes third correspondence information, where the third correspondence information is used to indicate that the random access corresponds to the first TAG.

[0290] S806 , the terminal sends an RRC reconfiguration completion message to the CU; correspondingly, the CU receives the RRC reconfiguration completion message.

[0291] S807 , the first DU sends a PDCCH order to the terminal, where the PDCCH order is used to instruct the terminal to send a random access preamble on the first cell; accordingly, the terminal receives the PDCCH order.

[0292] S808: The terminal sends a random access preamble on the first cell according to the PDCCH order; accordingly, the second DU receives the random access preamble.

[0293] S809: The second DU determines the first TA information according to the random access preamble, and sends a message 5 to the CU, where the message 5 includes the first TA information.

[0294] S810, the CU sends a message 6 to the first DU, where the message 6 includes first TA information; accordingly, the first DU receives the message 6 and obtains the first TA information.

[0295] S811: The terminal sends a measurement report to the first DU, where the measurement report includes lower layer measurement results of multiple candidate cells.

[0296] S812. The first DU sends a handover command message to the terminal, where the handover command message is used to instruct the terminal to handover to the first cell.

[0297] The handover command message includes identification information of the handover target cell and first TA information.

[0298] S813: The terminal determines that the first TA information corresponds to a first TAG, and uses the TA indicated by the first TA information to access the target cell.

[0299] Exemplarily, the terminal may determine that the first TA information corresponds to the first TAG according to the random access indicated by the RRC reconfiguration message.

[0300] S814, the first DU sends an LTM cell change notification (Cell Switch Notification) message to the CU, where the LTM cell change notification message is used to indicate that a cell switch command (Cell Switch Command) has been initiated for the terminal; accordingly, the CU receives the LTM cell change notification message.

[0301] Here, the LTM cell change notification message includes identification information of the target cell.

[0302] S815, the CU sends an LTM cell change notification message to the second DU; correspondingly, the second DU receives the LTM cell change notification message.

[0303] S816: The second DU determines that the terminal has acquired the TA corresponding to the first TAG.

[0304] S817, the second DU sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal determines that the switching is completed.

[0305] It is understood that the process illustrated in FIG8 corresponds to the process illustrated in FIG7 , and the steps of the two can be referenced to each other. For example, S801 to S805 correspond to S701 in Example 1, S807 to S812 correspond to S702 in Example 1, S813 corresponds to S703 in Example 1, S816 corresponds to S704 in Example 1, and S817 corresponds to S705 in Example 1.

[0306] Example 5

[0307] In the fifth embodiment, the interaction between the first network device, the second network device and the terminal is described as an example, wherein the first network device and the second network device can refer to the description of the first embodiment.

[0308] FIG9 is a flow chart of the communication method according to the fifth embodiment of the present application. As shown in FIG9 , the method includes:

[0309] S901: A second network device sends a fifth message to a terminal. The fifth message is used to indicate that a first TA measurement corresponds to a first TAG. In response, the terminal receives the fifth message. In one possible implementation, the fifth message may be an RRC reconfiguration message. There are various implementations for the second network device to send the fifth message to the terminal. For example, in scenario 2, the second network device may send the fifth message to the terminal via relay communication.

[0310] The above S901 may also be replaced by S901'. S901', the first network device sends a fifth message to the terminal, the fifth message being used to indicate that the first TA measurement corresponds to the first TAG; accordingly, the terminal receives the fifth message. In one possible implementation, the fifth message is a handover command message.

[0311] The first TAG is one of multiple TAGs, and the multiple TAGs correspond to the first cell (that is, the second network device allocates multiple TAGs to the terminal for the first cell). For example, the multiple TAGs include a first TAG and a second TAG, for example, the first TAG corresponds to a first TRP, the second TAG corresponds to a second TRP, the first TRP and the second TRP correspond to the first cell, and the first TRP and the second TRP correspond to different reference signals. For example, the reference signal can be a channel state information reference signal (CSI-RS) or an SSB.

[0312] Optionally, the fifth message is further used to indicate that the second TA measurement corresponds to the second TAG.

[0313] Here, "the first TA measurement corresponds to the first TAG" may mean that the first reference signal of the first cell corresponds to the first TAG. "The second TA measurement corresponds to the second TAG" may mean that the second reference signal of the first cell corresponds to the second TAG. For example, the fifth message includes fourth correspondence information, which is used to indicate that the first TA measurement corresponds to the first TAG; the fourth correspondence information may include configuration information of the first reference signal (such as identification information of the first reference signal) and identification information of the first TAG corresponding to the first reference signal. Optionally, the fifth message also includes fifth correspondence information, which is used to indicate that the second TA measurement corresponds to the second TAG; the fifth correspondence information includes configuration information of the second reference signal and identification information of the second TAG corresponding to the second reference signal. In addition, the fifth message also includes a first measurement identifier corresponding to the first reference signal and a second measurement identifier corresponding to the second reference signal. For example, the first reference signal includes SSB0 to SSB10, and the second reference signal includes SSB11 to SSB20. The first measurement identifier and the second measurement identifier may be the same or different.

[0314] In a possible example, the fifth message includes a TAG identifier (eg, the first TAG identifier or the second TAG identifier), and the TAG identifier can also be used to indicate the TAG corresponding to the first TA measurement.

[0315] It should be noted that “the first TA measurement corresponds to the first TAG” can also be understood as the TA determined by the terminal based on the first TA measurement corresponds to the first TAG. “The second TA measurement corresponds to the second TAG” can also be understood as the TA determined by the terminal based on the second TA measurement corresponds to the second TAG.

[0316] In a possible example, in S901, the fifth message is an RRC reconfiguration message, which also includes LTM configuration information of the first cell. The fourth correspondence information (and the fifth correspondence information) may be included in the LTM configuration information of the first cell.

[0317] In another possible example, in S901', the fifth message is a handover command message, which is transmitted via MAC CE. The fourth correspondence information (and the fifth correspondence information) may be sent by the second network device to the first network device, and then sent by the first network device to the terminal via the handover command message. In this case, the second network device sends an RRC reconfiguration message to the terminal, and the RRC reconfiguration message includes the LTM configuration information of the first cell, such as the RRC reconfiguration message indicating that the first reference signal corresponds to the first measurement identifier; the first network device sends a handover command message to the terminal, such as the handover command message includes the fourth correspondence information (and the fifth correspondence information). The RRC reconfiguration message is sent to the terminal before the handover command message.

[0318] In addition, the first network device (i.e., the network device to which the source cell of the terminal belongs) can send configuration information of the second cell (for example, the second cell is the source cell) to the terminal, for example, the configuration information of the source cell includes the configuration information of the third reference signal of the source cell and the third measurement identifier corresponding to the third reference signal.

[0319] S902: The terminal measures and obtains the first TA according to the first TA.

[0320] Exemplarily, the terminal may obtain the first TA based on the first TA measurement by: measuring the first reference signal to obtain the first downlink timing; and measuring the third reference signal to obtain the third downlink timing. When the first measurement identifier and the third measurement identifier are the same, the terminal calculates the first TA based on the first downlink timing, the third downlink timing, and the TA of the source cell, with reference to Formula 1 or Formula 2 above for details.

[0321] Optionally, the terminal further obtains the second TA based on the second TA measurement. Specifically, this may be achieved by: the terminal measuring the second reference signal to obtain the second downlink timing; and measuring the third reference signal to obtain the third downlink timing. When the second measurement identifier and the third measurement identifier are the same, the terminal calculates the second TA based on the second downlink timing, the third downlink timing, and the TA of the source cell, as described in Formula 1 or Formula 2 above.

[0322] S903: The terminal determines, according to the fifth message, that the first TA corresponds to the first TAG.

[0323] For example, the terminal determines that the first TA corresponds to the first TAG according to the correspondence between the first TA measurement and the first TAG in the fifth message.

[0324] In one possible implementation, the terminal determines that the first TA corresponds to the first TAG based on the correspondence between the first reference signal in the fifth message and the first TAG. Optionally, the terminal determines that the second TA corresponds to the second TAG based on the correspondence between the second reference signal in the fifth message and the second TAG.

[0325] It should be noted that, when the fifth message is a handover command message, the execution order of the above steps is: S902->S901'->S903. When the fifth message is an RRC reconfiguration message (i.e., a message different from the handover command message), the execution order of the above steps is: S901->S902->S903.

[0326] S904: The second network device determines that the terminal has acquired the TA corresponding to the first TAG according to the first TA measurement.

[0327] Exemplarily, if the first network device determines to handover the terminal to the first cell, it sends a handover command message to the terminal. The handover command message includes identification information of the target cell to be handed over, where the target cell is the first cell. Accordingly, after receiving the handover command message, the terminal can access the first cell using the first TA. In this case, the handover command message may not include TA information.

[0328] Exemplarily, the second network device can allocate uplink resources to the terminal (for example, the uplink resources correspond to the first TAG), and then the terminal can use the first TA to send uplink information to the second network device on the uplink resources; accordingly, after the second network device receives the uplink information, it can determine that the terminal has successfully accessed the target cell. Since the second network device receives the uplink information on the uplink resources corresponding to the first TAG, the second network device can determine that the terminal has obtained the TA corresponding to the first TAG. Alternatively, after successfully accessing the first cell, the terminal sends a first indication message to the second network device, and the first indication message is used to indicate that the terminal has obtained the TA corresponding to the first TAG. Alternatively, the first network device sends the first indication message to the second network device, for example, after the first network device sends a handover command message to the terminal, it sends the first indication message to the second network device. For example, there is a correspondence b between TCI state 1 and the first TAG, and the first indication information may be the identification information of TCI state 1. The identification information of TCI state 1 is also indicated to the terminal in the switching command message, and is used to indicate the beam corresponding to the PDCCH or PDSCH of the target cell of the terminal. The second network device determines that the terminal has obtained the TA corresponding to the first TAG based on the identification information of TCI state 1 and the correspondence b.

[0329] Optionally, the second network device can also determine that the terminal has obtained the TA corresponding to the second TAG. For example, after accessing the first cell, the terminal sends a second indication message to the second network device, and the second indication message is used to indicate that the terminal has obtained the TA corresponding to the second TAG. Alternatively, the first network device sends the second indication message to the second network device, for example, after the first network device sends a handover command message to the terminal, it sends the second indication message to the second network device. For example, there is a correspondence c between TCI state 2 and the second TAG, and the first indication information can be the identification information of TCI state 2. The identification information of TCI state 2 is also indicated to the terminal in the handover command message, and is used to indicate the beam corresponding to the PDCCH or PDSCH of the target cell of the terminal. The second network device determines that the terminal has obtained the TA corresponding to the second TAG based on the identification information of TCI state 2 and the correspondence c.

[0330] Exemplarily, when the terminal receives the second message and obtains the first TA based on the first TA measurement, the terminal starts the timer corresponding to the first TAG (i.e., the first timing advance timer); for example, when the terminal receives the second message, the terminal starts the timer corresponding to the first TAG (i.e., the first timing advance timer). During the operation of the first timing advance timer, it can be considered that the terminal is uplink synchronized with the first TAG of the target cell. If the first TA is not obtained, there is no need to start the timer corresponding to the first TAG.

[0331] Exemplarily, when the terminal receives the second message and obtains the second TA according to the second TA measurement, the terminal starts the timer corresponding to the second TAG (i.e., the second timing advance timer); for example, when the terminal receives the second message, the terminal starts the timer corresponding to the second TAG (i.e., the second timing advance timer). During the running of the second timing advance timer, it can be considered that the terminal is uplink synchronized with the second TAG of the target cell. If the second TA is not obtained, there is no need to start the timer corresponding to the second TAG.

[0332] The duration of the first timing advance timer and / or the duration of the second timing advance timer is provided to the terminal by the second network device.

[0333] Optionally, the above method further includes:

[0334] S905, the second network device sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal can determine that the switching is completed.

[0335] The above S905 may refer to S507 in the first embodiment.

[0336] Using the above method, the second network device indicates to the terminal that the first TA measurement corresponds to the first TAG, so that after the terminal obtains the first TA information based on the first TA measurement, it can determine that the first TA information corresponds to the first TAG, which facilitates the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0337] Example 6

[0338] In the sixth embodiment, based on the fifth embodiment, a possible implementation process will be described by taking scenario 2 as an example.

[0339] FIG10 is a flow chart of the communication method according to the sixth embodiment of the present application. As shown in FIG10 , the method includes:

[0340] S1001: The CU sends a message 1 to the second DU. The message 1 is used to request LTM configuration.

[0341] Exemplarily, the message 1 may include request information, where the request information is used to request TA measurement configuration of multiple TAGs.

[0342] S1002 , the second DU sends message 2 to the CU, where message 2 includes LTM configuration information of the first cell; accordingly, the CU receives message 2 .

[0343] Here, the LTM configuration information of the first cell includes the lower layer RRC configuration, reference signal configuration, transmission configuration indication state configuration and random access channel configuration of the first cell. Message 2 also includes fourth correspondence information (and fifth correspondence information).

[0344] For example, when message 1 includes request information, message 2 includes the fourth correspondence information (and the fifth correspondence information). Alternatively, message 1 may not include request information. In this case, the second DU actively sends the fourth correspondence information (and the fifth correspondence information).

[0345] S1003 , the CU sends message 3 to the first DU; correspondingly, the first DU receives message 3 .

[0346] Exemplarily, message 3 also includes the reference signal configuration of the first cell, the TCI state configuration of the first cell, and the RACH configuration of the first cell.

[0347] S1004 , the first DU sends message 4 to the CU; correspondingly, the CU receives message 4 .

[0348] 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.

[0349] The message names of messages 1 to 4 may refer to the description in the second embodiment.

[0350] S1005. The CU sends an RRC reconfiguration message to the terminal; accordingly, the terminal receives the RRC reconfiguration message.

[0351] Here, the RRC reconfiguration message includes the fourth correspondence information (and the fifth correspondence information).

[0352] S1006. The terminal sends an RRC reconfiguration completion message to the CU; accordingly, the CU receives the RRC reconfiguration completion message.

[0353] S1007: The terminal measures and obtains the first TA according to the first TA.

[0354] S1008: The terminal determines, according to the fourth correspondence information in the RRC reconfiguration message, that the first TA corresponds to the first TAG.

[0355] Optionally, the terminal obtains the second TA according to the second TA measurement; and determines, according to the fifth corresponding relationship information in the RRC reconfiguration message, that the second TA corresponds to the second TAG.

[0356] S1009: The terminal sends a measurement report to the first DU, where the measurement report includes lower layer measurement results of multiple candidate cells.

[0357] S1010. The first DU sends a handover command message to the terminal, where the handover command message is used to instruct the terminal to handover to the first cell.

[0358] The handover command message includes identification information of a target cell to be handed over, and the target cell is the first cell.

[0359] S1011: The terminal accesses the target cell using the TA indicated by the first TA according to the handover command message.

[0360] S1012: 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.

[0361] Here, the LTM cell change notification message includes identification information of the target cell.

[0362] S1013, the CU sends an LTM cell change notification message to the second DU; correspondingly, the second DU receives the LTM cell change notification message.

[0363] S1014: The second DU determines that the terminal has acquired the TA corresponding to the first TAG according to the first TA measurement.

[0364] S1015, the second DU sends downlink control information to the terminal, where the downlink control information is used to indicate uplink resources or downlink resources; accordingly, the terminal receives the downlink control information, and when the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal determines that the switching is completed.

[0365] It is understood that the process illustrated in FIG10 corresponds to the process illustrated in FIG9 , and the steps of the two can be referenced to each other. For example, S1001 to S1005 correspond to S901 in the first embodiment, S1007 corresponds to S902 in the first embodiment, S1008 corresponds to S903 in the first embodiment, S1014 corresponds to S904 in the first embodiment, and S1015 corresponds to S905 in the first embodiment.

[0366] With respect to the above embodiments, it can be understood that:

[0367] (1) In various embodiments of the present application, "correspond" may be replaced by "associate," "correlate," or "map." Taking "a first tag corresponds to the first information" as an example, the correspondence between the first tag and the first information means that, when there are multiple tags, the first tag among the multiple tags can be indexed through the first information.

[0368] (2) In the various embodiments of this application, unless otherwise specified or logically conflicting, the terms and / or descriptions between different embodiments are consistent and may be referenced to each other. The technical features in different embodiments may be combined to form new embodiments based on their inherent logical relationships. In addition, within the same embodiment, different implementations or different examples may also reference or refer to each other.

[0369] (3) The various numerical numbers involved in this application are only for the convenience of description and are not used to limit the scope of this application. The step numbers of the above-mentioned flowcharts are only an example of the execution process and do not constitute a restriction on the order of execution of the steps. That is, the size of the step numbers does not mean the order of execution. The execution order of each step should be determined by its function and internal logic. In addition, not all the steps shown in the flowcharts are required to be executed. Some steps can be added or deleted based on actual needs.

[0370] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between the network device and the terminal. It is understandable that in order to implement the above functions, the network device and the terminal may include hardware structures and / or software modules corresponding to the execution of 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.

[0371] In the embodiments of the present application, network devices and terminals can be divided into functional units according to the above method examples. For example, functional units can be divided according to different functions, or two or more functions can be integrated into one unit. The above integrated units can be implemented in the form of hardware or software functional units.

[0372] In the case of adopting an integrated unit, Figure 11 shows a possible exemplary block diagram of the device involved in the embodiments of the present application. As shown in Figure 11, the device 1100 may include: a processing unit 1102 and a communication unit 1103. The processing unit 1102 is used to control and manage the actions of the device 1100. The communication unit 1103 is used to support the communication between the device 1100 and other devices. Optionally, the communication unit 1103 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 1100 may also include a storage unit 1101 for storing program code and / or data of the device 1100.

[0373] (1) Apparatus 1100 may be the first network device in the aforementioned embodiment. Processing unit 1102 may support apparatus 1100 in executing the actions of the first network device in each of the aforementioned method examples. Alternatively, processing unit 1102 may primarily execute internal actions of the first network device in the method examples, and communication unit 1103 may support communication between apparatus 1100 and other devices.

[0374] For example, in one embodiment, the communication unit 1103 is used to: receive a first message, the first message including first timing advance TA information of a first cell; determine that the first TA information corresponds to a first TAG in multiple timing advance groups TAG, and the multiple TAGs correspond to the first cell; send a second message to the terminal, the second message including identification information of a target cell for switching of the terminal, the first TA information and identification information of the first TAG corresponding to the first TA information, and the target cell is the first cell.

[0375] In one possible design, the first message also includes first information corresponding to the first TA information; the communication unit 1103 is also used to: receive a third message, and the third message is used to indicate that the first TAG corresponds to the first information; the processing unit 1102 is used to: determine that the first TA information corresponds to the first TAG based on the first message and the third message.

[0376] In one possible design, the processing unit 1102 is specifically used to determine that the first TA information corresponds to the first TAG based on the correspondence between the first TA information and the first information, and the correspondence between the first TAG and the first information.

[0377] In one possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; wherein the first TRP corresponds to the first cell.

[0378] In one possible design, the communication unit 1103 is further used to: send first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0379] In one possible design, the first message also includes the second TA information of the first cell; the processing unit 1102 is specifically used to: determine that the second TA information corresponds to the second TAG among the multiple TAGs; the second message also includes the second TA information and the identification information of the second TAG corresponding to the second TA information.

[0380] In one possible design, the communication unit 1103 is further used to: send second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0381] (2) The apparatus 1100 may be a terminal in the aforementioned embodiments. The processing unit 1102 may support the apparatus 1100 in executing the terminal actions in the aforementioned method examples. Alternatively, the processing unit 1102 primarily executes the internal actions of the terminal in the method examples, and the communication unit 1103 may support communication between the apparatus 1100 and other devices.

[0382] For example, in one embodiment, the communication unit 1103 is used to: receive a second message, the second message including identification information of a target cell for terminal switching, first TA information and identification information of a first TAG, the first TAG being one of a plurality of TAGs, and the plurality of TAGs corresponding to the target cell; the processing unit 1102 is used to: determine, according to the second message, that the first TA information corresponds to the first TAG, and access the target cell using the TA indicated by the first TA information.

[0383] In one possible design, the processing unit 1102 is further used to: start the timer corresponding to the first TAG when the second message is received; wherein, during the operation of the timer, the terminal is uplink synchronized with the target cell.

[0384] In one possible design, the communication unit 1103 is also used to: receive downlink control information on the target cell, where the downlink control information is used to indicate resources, which are uplink resources or downlink resources; the processing unit 1102 is also used to: determine that the switching is completed when the downlink control information or the resources indicated by the downlink control correspond to the first TAG.

[0385] In one possible design, the communication unit 1103 is further used to: send first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0386] In one possible design, the second message also includes second TA information and identification information of the second TAG; the processing unit 1102 is also used to: determine, based on the second message, that the second TA information corresponds to the second TAG.

[0387] In one possible design, the communication unit 1103 is further used to: send second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0388] (3) The apparatus 1100 may be the second network device in the above-described embodiments. The processing unit 1102 may support the apparatus 1100 in executing the actions of the second network device in each of the above-described method examples. Alternatively, the processing unit 1102 may primarily execute the internal actions of the second network device in the method examples, and the communication unit 1103 may support communication between the apparatus 1100 and other devices.

[0389] For example, in one embodiment, the communication unit 1103 is used to: send a third message, wherein the third message is used to indicate that the first TAG among multiple TAGs corresponds to the first information, and the multiple TAGs correspond to the first cell; send a first message, wherein the first message includes first TA information and the first information corresponding to the first TA information; wherein the first message and the third message are used to determine that the first TA information corresponds to the first TAG; the processing unit 1102 is used to: determine that the terminal has obtained the TA corresponding to the first TAG.

[0390] In one possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; wherein the first TRP corresponds to the first cell.

[0391] In one possible design, the communication unit 1103 is further used to: receive request information, where the request information is used to request random access configuration corresponding to the multiple TAGs.

[0392] In one possible design, the communication unit 1103 is further used to: receive first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0393] In one possible design, the third message is also used to indicate that the second TAG among the multiple TAGs corresponds to the second information, and the first message also includes the second TA information and the second information corresponding to the second TA information; wherein the first message and the third message are also used to determine that the second TA information corresponds to the second TAG; the communication unit 1103 is also used to: receive second indication information, and the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

[0394] 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.

[0395] 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).

[0396] 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.

[0397] Referring to Figure 12, 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 12, the network device 120 can be an access network device, and the network device 120 may include one or more DUs 1201 and one or more CUs 1202. The DU 1201 may include at least one antenna 12011, at least one radio frequency unit 12012, at least one processor 12013 and at least one memory 12014. The DU 1201 is mainly used for receiving and transmitting radio frequency signals, converting radio frequency signals into baseband signals, and partial baseband processing. The CU 1202 may include at least one processor 12022 and at least one memory 12021.

[0398] The CU 1202 is primarily used for baseband processing and controlling network devices. The DU 1201 and CU 1202 can be physically located together or separately, i.e., in a distributed base station. The CU 1202 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 1202 can be used to control the network device to execute the network device operation process described in the above method embodiments.

[0399] In addition, the network device 120 may optionally include one or more radio frequency units (RFUs), one or more DUs (DUs), and one or more CUs. The DUs may include at least one processor 12013 and at least one memory 12014, the RFUs may include at least one antenna 12011 and at least one RFU 12012, and the CUs may include at least one processor 12022 and at least one memory 12021.

[0400] In one example, the CU1202 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 separately support wireless access networks with different access standards (such as an LTE network, a 5G network, or other networks). The memory 12021 and the processor 12022 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 DU1201 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 separately support wireless access networks with different access standards (such as an LTE network, a 5G network, or other networks). The memory 12014 and the processor 12013 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.

[0401] The network device shown in Figure 12 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 Figure 12 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.

[0402] Refer to Figure 13, 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 13, the terminal includes: an antenna 1310, a radio frequency part 1320, and a signal processing part 1330. The antenna 1310 is connected to the radio frequency part 1320. In the downlink direction, the radio frequency part 1320 receives information sent by the network device through the antenna 1310, and sends the information sent by the network device to the signal processing part 1330 for processing. In the uplink direction, the signal processing part 1330 processes the information of the terminal and sends it to the radio frequency part 1320. The radio frequency part 1320 processes the information of the terminal and sends it to the network device through the antenna 1310.

[0403] The signal processing unit 1330 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.

[0404] The modem subsystem may include one or more processing elements 1331, such as a main control CPU and other integrated circuits. Furthermore, the modem subsystem may include a storage element 1332 and an interface circuit 1333. Storage element 1332 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 1332 but rather in a memory external to the modem subsystem, and loaded by the modem subsystem when in use. Interface circuit 1333 is used to communicate with other subsystems.

[0405] 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.

[0406] 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.

[0407] 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.

[0408] 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.

[0409] 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.

[0410] The processing element here is the same as described above and can be implemented by a processor. The function of the processing element can be the same as that of the processing unit described in Figure 11. 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 function of the storage element can be the same as that of the storage unit described in Figure 11. The storage element can be a single memory or a collective term for multiple memories.

[0411] The terminal shown in FIG13 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 FIG13 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.

[0412] 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.

[0413] 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.

[0414] 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.

[0415] 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.

[0416] 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.

Claims

1. A communication method, characterized in that: The method comprises: receiving a first message, wherein the first message includes first timing advance (TA) information of a first cell; Determine that the first TA information corresponds to a first TAG among multiple timing advance groups TAGs, and the multiple TAGs correspond to the first cell; A second message is sent to the terminal, wherein the second message includes identification information of a target cell for switching of the terminal, the first TA information, and identification information of the first TAG corresponding to the first TA information, and the target cell is the first cell.

2. The method according to claim 1, characterized in that The first message also includes first information corresponding to the first TA information; The method further comprises: receiving a third message, where the third message is used to indicate that the first TAG corresponds to the first information; Determining that the first TA information corresponds to a first TAG among multiple TAGs includes: According to the first message and the third message, it is determined that the first TA information corresponds to the first TAG.

3. The method according to claim 2, characterized in that Determining, according to the first message and the third message, that the first TA information corresponds to the first TAG includes: According to the correspondence between the first TA information and the first information, and the correspondence between the first TAG and the first information, it is determined that the first TA information corresponds to the first TAG.

4. The method according to claim 2 or 3, characterized in that: The first information indicates at least one of the following: first TRP; first SSB; first random access resource; Among them, the first TRP corresponds to the first cell.

5. The method according to any one of claims 1 to 4, characterized in that The method further comprises: Send first indication information, where the first indication information is used to indicate that the terminal has acquired a TA corresponding to the first TAG.

6. The method according to any one of claims 1 to 5, characterized in that The first message also includes second TA information of the first cell; The method further includes: determining that the second TA information corresponds to a second TAG among the plurality of TAGs; The second message also includes the second TA information and identification information of a second TAG corresponding to the second TA information.

7. The method according to claim 6, characterized in that The method further comprises: Send second indication information, where the second indication information is used to indicate that the terminal has acquired the TA corresponding to the second TAG.

8. A communication method, characterized in that: The method comprises: receiving a second message, where the second message includes identification information of a target cell for handover of the terminal, first TA information, and identification information of a first TAG, where the first TAG is one of a plurality of TAGs, and the plurality of TAGs correspond to the target cell; According to the second message, it is determined that the first TA information corresponds to the first TAG, and the target cell is accessed using the TA indicated by the first TA information.

9. The method according to claim 8, characterized in that The method further comprises: When the second message is received, a timer corresponding to the first TAG is started; wherein, during the running of the timer, the terminal is uplink synchronized with the target cell.

10. The method according to claim 8 or 9, characterized in that: The method further comprises: receiving downlink control information on the target cell, where the downlink control information is used to indicate a resource, and the resource is an uplink resource or a downlink resource; In a case where the downlink control information or the resource indicated by the downlink control corresponds to the first TAG, it is determined that the switching is completed.

11. The method according to any one of claims 8 to 10, characterized in that The method further comprises: Send first indication information, where the first indication information is used to indicate that the terminal has acquired a TA corresponding to the first TAG.

12. The method according to any one of claims 8 to 11, characterized in that The second message also includes second TA information and identification information of the second TAG; The method also includes: determining, according to the second message, that the second TA information corresponds to the second TAG.

13. The method according to claim 12, characterized in that The method further comprises: Send second indication information, where the second indication information is used to indicate that the terminal has acquired the TA corresponding to the second TAG.

14. A communication method, characterized in that: The method comprises: Sending a third message, where the third message is used to indicate that a first TAG among multiple TAGs corresponds to the first information, and the multiple TAGs correspond to the first cell; Sending a first message, where the first message includes first TA information and the first information corresponding to the first TA information; wherein the first message and the third message are used to determine that the first TA information corresponds to the first TAG; It is determined that the terminal has acquired the TA corresponding to the first TAG.

15. The method according to claim 14, characterized in that The first information indicates at least one of the following: first TRP; first SSB; first random access resource; Among them, the first TRP corresponds to the first cell.

16. The method according to claim 14 or 15, characterized in that The method further comprises: Receive request information, where the request information is used to request random access configurations corresponding to the multiple TAGs.

17. The method according to any one of claims 14 to 16, characterized in that Determining that the terminal has acquired the TA corresponding to the first TAG includes: First indication information is received, where the first indication information is used to indicate that the terminal has acquired a TA corresponding to the first TAG.

18. The method according to any one of claims 14 to 17, characterized in that The third message is further used to indicate that a second TAG among the multiple TAGs corresponds to the second information, and the first message also includes the second TA information and the second information corresponding to the second TA information; wherein the first message and the third message are further used to determine that the second TA information corresponds to the second TAG; The method further comprises: Receive second indication information, where the second indication information is used to indicate that the terminal has acquired a TA corresponding to a second TAG.

19. A communication device, characterized in that: Comprising means for executing the method as claimed in any one of claims 1 to 18.

20. A communication device, characterized in that: It includes a processor, the processor 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 according to any one of claims 1 to 18.

21. 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 7, the terminal is used to execute the method described in any one of claims 8 to 13, and the second network device is used to execute the method described in any one of claims 14 to 18.

22. A computer-readable storage medium, characterized in that: The storage medium stores a computer program or instruction. When the computer program or instruction is executed by a computer, the method according to any one of claims 1 to 7, or the method according to any one of claims 8 to 13, or the method according to any one of claims 14 to 18 is implemented.

23. 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 7, or the method according to any one of claims 8 to 13, or the method according to any one of claims 14 to 18.

Images