Communication method and device

Abstract

The invention relates to the technical field of communication, and discloses a communication method and device. 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 in a plurality of TAGs, wherein the plurality of TAGs correspond to a first cell; and sending a second message to the terminal, the second message comprising 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 being the first cell. Through adoption of the method, the first network equipment determines that the first TA information corresponds to the first TAG, and then 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, the terminal can perform effective data transmission on the target cell quickly, and the data transmission efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and in particular, to a communication method and apparatus. Background Art

[0002] Currently, multiple input and multiple output (MIMO) technology has been introduced into communication systems to improve throughput. MIMO technology means that multiple transmit antennas and multiple receive antennas are respectively used at the transmitting end and the receiving end, that is, there are multiple independent channels between the transmitting end and the receiving end. On this basis, the 5th Generation (5G) communication system has introduced MIMO transmission technology based on multiple transmission and reception points (TRPs). A TRP can be understood as a physical transceiver point, and the coverage of a cell can be jointly provided by the coverage of multiple TRPs, thereby ensuring full coverage.

[0003] However, after the introduction of multi-TRP transmission technology, in the cell handover scenario, how to ensure that the terminal can quickly perform effective data transmission on the target cell still needs further research. Summary of the Invention

[0004] This application provides a communication method and apparatus, which are used to enable a terminal to obtain the correspondence between the timing advance (TA) and the timing advance group (TAG) of a target cell in a cell handover scenario, so as to facilitate the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0005] In a first aspect, an embodiment of this application provides a communication method. This method can be applied to a first network device or a module (such as a chip or a 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, and the first message includes the first timing advance (TA) information of a first cell; determines that the first TA information corresponds to a first timing advance group (TAG) among multiple timing advance groups (TAGs), and the multiple TAGs correspond to the first cell; and sends a second message to the terminal, where the second message includes the identification information of the target cell for the handover of the terminal, the first TA information, and the identification information of the first TAG corresponding to the first TA information, and the target cell is the first cell.

[0006] By 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 the correspondence between the first TA information and the first TAG, which is convenient for the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0007] In a possible design, the first message further includes first information corresponding to the first TA information; the method further includes: 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: determining, according to the first message and the third message, that the first TA information corresponds to the first TAG.

[0008] In a possible design, determining that the first TA information corresponds to the first TAG according to the first message and the third message includes: determining that the first TA information corresponds to the first TAG according to the correspondence between the first TA information and the first information, and the correspondence between the first TAG and the first information.

[0009] In a possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; where the first TRP corresponds to the first cell.

[0010] In a 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.

[0011] In this way, by sending the first indication information, the second network device can determine, according to the first indication information, that the terminal has obtained the TA corresponding to the first TAG, which is convenient for subsequent scheduling of the terminal to perform data transmission of the first TAG.

[0012] In a possible design, the first message further 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 multiple TAGs; the second message further includes the second TA information and identification information of the second TAG corresponding to the second TA information.

[0013] 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 is convenient for subsequent rapid data transmission of the second TAG.

[0014] In a 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.

[0015] 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 a circuit). Taking the method applied to the terminal as an example, in this method, the terminal receives a second message, and 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 TA indicated by the first TA information is used to access the target cell.

[0016] In a possible design, the method further includes: starting a timer corresponding to the first TAG when receiving the second message; where during the running of the timer, the terminal is uplink synchronized with the target cell.

[0017] In a possible design, the method further includes: 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; determining that the handover is completed when the downlink control information or the resource indicated by the downlink control corresponds to the first TAG.

[0018] In a 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.

[0019] In a possible design, the second message further includes second TA information and identification information of a second TAG; the method further includes: according to the second message, determining that the second TA information corresponds to the second TAG.

[0020] In a 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.

[0021] Third aspect, an embodiment of the present application provides a communication method, which can be applied to a second network device or a module in the second network device (such as a chip or a circuit). Taking the method applied to the second network device as an example, in this method, the second network device sends a third message, where the third message is used to indicate that a first TAG among a plurality of TAGs corresponds to first information, and the plurality of TAGs correspond to a first cell; sending a first message, where the first message includes first TA information and the first information corresponding to the first TA information; where the first message and the third message are used to determine that the first TA information corresponds to the first TAG; determining that the terminal has obtained the TA corresponding to the first TAG.

[0022] In a 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.

[0023] In a possible design, the method further includes: receiving request information for requesting a random access configuration corresponding to the plurality of TAGs.

[0024] In a possible design, determining that the terminal has obtained a TA corresponding to the first TAG includes: receiving first indication information for indicating that the terminal has obtained a TA corresponding to the first TAG.

[0025] In a possible design, the third message is further used to indicate that a second TAG among the plurality of TAGs corresponds to second information, and the first message further includes 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 includes: receiving second indication information for indicating that the terminal has obtained a TA corresponding to the second TAG.

[0026] It can be understood that the communication method provided in the second aspect or the third aspect corresponds to the first aspect. 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 elaborated here.

[0027] 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 a circuit). Taking the method applied to the terminal as an example, in this method, the terminal receives a fourth message, the fourth message is used to indicate that random access corresponds to a first TAG, the first TAG is one of a plurality of TAGs, and the plurality of TAGs correspond to a first cell; obtaining first TA information according to the random access; determining that the first TA information corresponds to the first TAG according to the fourth message.

[0028] By adopting 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 is convenient for the terminal to quickly perform effective data transmission on the target cell and improve the data transmission efficiency.

[0029] In a possible design, obtaining the first TA according to the random access includes: receiving a second message, where the second message includes identification information of a target cell for handover of the terminal and the first TA information, and the target cell is the first cell; the method further includes: when the second message is received, starting a timer corresponding to the first TAG, and during the running of the timer, the terminal is uplink synchronized with the target cell.

[0030] In a possible design, the method further includes: accessing the target cell for handover using the TA indicated by the first TA information, where the target cell is the first cell; receiving downlink control information on the first cell, where the downlink control information is used to indicate a resource, and the resource is an uplink resource or a downlink resource; when the downlink control information or the resource indicated by the downlink control information corresponds to the first TAG, determining that the handover is completed.

[0031] In a 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.

[0032] 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 a 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, where 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; determining that the terminal has obtained the TA corresponding to the first TAG according to the random access.

[0033] In a 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.

[0034] In a possible design, the method further includes: receiving request information, where the request information is used to request the random access configuration corresponding to the multiple TAGs.

[0035] 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.

[0036] 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 a circuit). Taking the method applied 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 a plurality of TAGs, and the plurality of TAGs correspond to a first cell; according to the first TA measurement, obtain a first TA; according to the fifth message, determine that the first TA corresponds to the first TAG.

[0037] By adopting the above method, the second network device indicates to the terminal that the first TA measurement corresponds to the first TAG, so that the terminal can determine that the first TA information corresponds to the first TAG after obtaining the first TA information according to the first TA measurement, which is convenient for the terminal to quickly perform effective data transmission on the target cell and improve the data transmission efficiency.

[0038] In a possible design, the method further includes: receiving a second message, where the second message includes identification information of a target cell for a handover of the terminal, and the target cell is the first cell; when receiving the second message and obtaining the first TA according to the first TA measurement, start a timer corresponding to the first TAG, and during the running of the timer, the terminal is uplink synchronized with the target cell.

[0039] In a possible design, the method further includes: accessing the target cell for handover using the first TA, where the target cell is the first cell; receiving downlink control information on the first cell, and the downlink control information is used to indicate a resource, and the resource is an uplink resource or a downlink resource; when the downlink control information or the resource indicated by the downlink control information corresponds to the first TAG, determine that the handover is completed.

[0040] In a possible design, that the first TA measurement corresponds to the first TAG includes: a first reference signal of the first cell corresponds to the first TAG, and the first reference signal is used for the first TA measurement.

[0041] In a possible design, the method further includes: sending a first indication message, where the first indication message is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0042] In a possible design, the fourth message is further used to indicate that a second TA measurement corresponds to the second TAG, and the second TAG is one of the plurality of TAGs; according to the second TA measurement, obtain a second TA; according to the fourth message, determine that the second TA corresponds to the second TAG.

[0043] In a 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.

[0044] In a 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.

[0045] In a possible design, the fifth message is further used to indicate the measurement identifier corresponding to the first reference signal; obtaining the first TA according to the first TA measurement includes: receiving the measurement identifier corresponding to the third reference signal of the second cell; when the measurement identifier corresponding to the first reference signal is the same as the measurement identifier corresponding to the third reference signal, determining the first TA according to the first reference signal, the third reference signal, and the TA of the second cell.

[0046] In a 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 a 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, where 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 according to the first TA measurement.

[0047] In a possible design, determining that the terminal has obtained the TA corresponding to the first TAG according to 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.

[0048] In a 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.

[0049] In a 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.

[0050] In a possible design, the fourth message is further used to indicate that the second TA measurement corresponds to the second TAG, and the second TAG is one of the multiple TAGs.

[0051] In a possible design, the method further includes: receiving second indication information, where the second indication information is used to indicate that the terminal has acquired the TA corresponding to the second TAG.

[0052] In a 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.

[0053] It can be understood that the communication method provided in the seventh aspect corresponds to the sixth aspect. 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 elaborated here.

[0054] In an eighth aspect, the present application provides a communication device, and the communication device is capable of implementing the functions involved in any one of the first to seventh aspects above. For example, the communication device includes modules, units, or means corresponding to the operations involved in any one of the first to seventh aspects above. The functions, units, or means can be implemented by software, or by hardware, or by hardware executing corresponding software.

[0055] In a possible design, the communication device includes a processing unit and a communication unit. Among them, the communication unit can be used to transmit and receive signals to achieve communication between the communication device and other devices; the processing unit can be used to perform some internal operations of the communication device. The functions executed by the processing unit and the communication unit can correspond to the operations involved in any one of the first to seventh aspects above.

[0056] In a possible design, the communication device includes a processor, and the processor can be used to be coupled with a memory. The memory can store necessary computer programs or instructions for implementing the functions involved in any one of the first to seventh aspects above. The processor can execute the computer programs or instructions stored in the memory, and when the computer programs or instructions are executed, the communication device implements the methods in any possible design or implementation manner of the first to seventh aspects above.

[0057] In a possible design, the communication device includes a processor and a memory. The memory can store necessary computer programs or instructions for implementing the functions involved in any one of the first to seventh aspects above. The processor can execute the computer programs or instructions stored in the memory, and when the computer programs or instructions are executed, the communication device implements the methods in any possible design or implementation manner of the first to seventh aspects above.

[0058] In a possible design, the communication device includes a processor and an interface circuit. The processor is configured to communicate with other devices through the interface circuit and execute the methods in any possible design or implementation manner of the above first aspect to seventh aspect.

[0059] It can be understood that in the above eighth aspect, the processor can be implemented by hardware or 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 that implements by reading software code stored in a memory. In addition, the above processor can be one or more, and the memory can be one or more. The memory can be integrated with the processor, or the memory and the processor are separately arranged. In a specific implementation process, the memory can be integrated with the processor on the same chip, or can be separately arranged on different chips. The embodiments of the present application do not limit the type of the memory and the setting manner of the memory and the processor.

[0060] In a ninth aspect, the present application provides a communication system. The communication system may include a first network device, a second network device, and a terminal. The first network device is configured to execute the method described in the above first aspect, the second network device is configured to execute the method described in the above third aspect, and the terminal is configured to execute the method described in the above second aspect.

[0061] Alternatively, the communication system may include a second network device and a terminal. The second network device is configured to execute the method described in the above fifth aspect, and the terminal is configured to execute the method described in the above fourth aspect.

[0062] Alternatively, the communication system may include a second network device and a terminal. The second network device is configured to execute the method described in the above seventh aspect, and the terminal is configured to execute the method described in the above sixth aspect.

[0063] In a tenth aspect, the present application provides a computer-readable storage medium. The computer-readable storage medium stores computer-readable instructions. When a computer reads and executes the computer-readable instructions, the computer is caused to execute the method in any possible design of the above first aspect to seventh aspect.

[0064] Exemplarily, the computer-readable storage medium can be any available medium that can be accessed by a computer. By way of example but not limitation: the computer-readable medium can include a non-transitory computer-readable medium, random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), CD-ROM or other optical disc storage, 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.

[0065] In an eleventh aspect, the present application provides a computer program product, which, when read and executed by a computer, causes the computer to execute the method in any possible design of the above first aspect to seventh aspect.

[0066] In a twelfth aspect, the present application provides a chip (or chip system), the chip includes a processor, the processor is coupled to a memory, and is configured to read and execute a software program stored in the memory to implement the method in any possible design of the above first aspect to seventh aspect. Description of the Drawings

[0067] Figure 1 It is a schematic diagram of a communication system applicable to an embodiment of the present application;

[0068] Figure 2A It is a schematic diagram of a CU-DU separation architecture provided by an embodiment of the present application;

[0069] Figure 2B It is a schematic diagram of another CU-DU separation architecture provided by an embodiment of the present application;

[0070] Figure 3A It is a schematic diagram of a downlink timing difference provided by an embodiment of the present application;

[0071] Figure 3B It is a schematic diagram of a timing advance provided by an embodiment of the present application;

[0072] Figure 4A It is a schematic diagram of a multi-TRP transmission technology provided by an embodiment of the present application;

[0073] Figure 4B It is a schematic diagram of another multi-TRP transmission technology provided by an embodiment of the present application;

[0074] Figure 5 It is a schematic flowchart corresponding to the communication method provided in Embodiment 1 of the present application;

[0075] Figure 6 It is a schematic flowchart corresponding to the communication method provided in the second embodiment of this application;

[0076] Figure 7 It is a schematic flowchart corresponding to the communication method provided in the third embodiment of this application;

[0077] Figure 8 It is a schematic flowchart corresponding to the communication method provided in the fourth embodiment of this application;

[0078] Figure 9 It is a schematic flowchart corresponding to the communication method provided in the fifth embodiment of this application;

[0079] Figure 10 It is a schematic flowchart corresponding to the communication method provided in the sixth embodiment of this application;

[0080] Figure 11 It is a possible exemplary block diagram of the device involved in the embodiments of this application;

[0081] Figure 12 It is a schematic structural diagram of a network device provided in the embodiment of this application;

[0082] Figure 13 It is a schematic structural diagram of a terminal provided in the embodiment of this application. Detailed implementation manners

[0083] Next, the technical solutions in the embodiments of this application will be described in conjunction with the accompanying drawings in the embodiments of this application. The technical solutions in the embodiments of this 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, 5th generation (5G) mobile communication system, such as New Radio (NR) system, and future evolved communication systems, such as 6th generation (6G) mobile communication system, etc.

[0084] Aspects, embodiments or features of the present application will be presented in the context of a system 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 connection with the figures. Additionally, combinations of these solutions may be used.

[0085] In addition, in the embodiments of the present application, words such as "exemplarily" and "such as" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as an "example" in the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of the word "example" is intended to present concepts in a specific manner. In the embodiments of the present application, "of", "corresponding", and "corresponding" may sometimes be used interchangeably. It should be noted that when their differences are not emphasized, their intended meanings are the same.

[0086] The communication systems and service scenarios described in the embodiments of the present application are for more clearly illustrating the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those of ordinary skill in the art will know that with the evolution of the network architecture and the emergence of new service scenarios, the technical solutions provided by the embodiments of the present application are equally applicable to similar technical problems.

[0087] To facilitate understanding of the embodiments of the present application, first, Figure 1 the communication system shown in Figure 1 will be used as an example to detail the communication system applicable to the embodiments of the present application. As

[0088] (1) Terminal

[0089] The terminal can be a terminal with wireless transceiver function that accesses the above communication system, or a chip or chip system that can be set in the terminal. The terminal can also be referred to as user equipment (UE), terminal device, user device, access terminal, user unit, user station, mobile station (MS), remote station, remote terminal, mobile device, user terminal, terminal unit, terminal station, terminal device, wireless communication device, user agent or user device.

[0090] For example, the terminal in the embodiments of this application can be a mobile phone, personal digital assistant (PDA) computer, laptop computer, tablet (Pad), drone, computer with wireless transceiver function, machine type communication (MTC) terminal, virtual reality (VR) terminal, augmented reality (AR) terminal, internet of things (IoT) terminal, wireless terminal in industrial control, wireless terminal in self-driving, wireless terminal in remote medical, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home (such as game console, smart TV, smart speaker, smart refrigerator and fitness equipment, etc.), in-vehicle terminal, RSU with terminal function.

[0091] (2) Access network device

[0092] The access network device is a device located on the network side of the above communication system and having a wireless transceiver function, or a chip or chip system that can be set in the device.

[0093] For example, the access network device in the embodiments of the present application may be an access point (AP) in a Wi-Fi system, such as a home gateway, router, server, switch, bridge, etc., a base station, evolved Node B (eNB), radio network controller (RNC), base station controller (BSC), base transceiver station (BTS), home base station, baseband unit (BBU), wireless relay node, wireless backhaul node, transmission and reception point (TRP; or transmission point, TP), etc. It may also be a next generation NodeB (gNB) in a 5G system, or a network node constituting a gNB, such as a central unit (CU), distributed unit (DU), roadside unit (RSU) with base station functions, etc. Or it may also be a satellite, or various future forms of base stations.

[0094] (3) Communication between the terminal and the access network device

[0095] The communication between the terminal and the access network device follows a certain protocol layer structure. For example, the control plane protocol layer structure may include a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a media access control (MAC) layer, and a physical layer (PHY); the user plane protocol layer structure may include a PDCP layer, an RLC layer, a MAC layer, and a physical layer. In a possible implementation, a service data adaptation protocol (SDAP) layer may also be included above the PDCP layer. Among them, the SDAP layer, PDCP layer, RLC layer, MAC layer, and physical layer may also be collectively referred to as the access layer. For specific descriptions of the above protocol layers, reference may be made to the relevant technical specifications of the 3rd generation partnership project (3GPP).

[0096] Taking the following downlink data transmission as an example, the downlink data can be encapsulated correspondingly in each layer of the access network device. The data received by a certain layer from the upper layer of this layer is regarded as the service data unit (SDU) of this layer. After layer encapsulation, it becomes the protocol data unit (PDU), and then is passed to the next layer. For example, the data received by the PDCP layer entity from the SDAP layer can be called PDCP SDU. After the PDCP layer entity encapsulates the PDCP SDU, it obtains the PDCP PDU and sends it to the RLC layer; the PDCP PDU received by the RLC layer entity from the PDCP layer can be called RLC SDU. After the RLC layer entity encapsulates the RLC SDU, it obtains the RLC PDU and sends it to the MAC layer.

[0097] From the perspective of the terminal, after the physical layer of the terminal receives the transport block from the access network device, it can submit it layer by layer to the upper layer in sequence, and corresponding de-encapsulation can be performed in each layer. That is to say, the processing performed by each layer in the terminal can be the reverse process of the processing performed by each layer in the access network device.

[0098] (4) CU-DU separation architecture

[0099] Exemplarily, in some possible network structures, the access network device may include one or more centralized units (CUs) and one or more distributed units (DUs). Multiple DUs can be centrally controlled by one CU, and this architecture can be called the CU-DU separation architecture. As an example, the interface between the CU and the DU can be called the F1 interface. Among them, the control plane (CP) interface can be the F1-C interface, and the user plane (UP) interface can be the F1-U interface.

[0100] The processing functions of the CU and the DU can be divided according to the protocol layers of the wireless network: for example Figure 2A As shown, the functions of the PDCP layer and the 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 the CU and the DU according to the protocol layers is only an example, and it can also be divided in other ways. For example, the functions of the protocol layers above the RLC layer are set in the CU, and the functions of the protocol layers at and below the RLC layer are set in the DU. Another example is that the CU or the DU can be divided into functions with more protocol layers, or the CU or the DU can also be divided into partial processing functions of the protocol layers. The embodiments of the present application do not limit this.

[0101] 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 segmented, that is, the control plane and the user plane are separated and implemented by different entities, namely the control plane CU entity (i.e., the CU-CP entity) and the user plane CU entity (i.e., the 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 the E1 interface, the interface between the CU-CP entity and the DU can be the F1-C interface, and the interface between the CU-UP entity and the DU can be the 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, and one CU-UP can be connected to multiple DUs. Under the cooperation of multiple CU-CPs, one CU-UP can also be connected to multiple cooperating CU-CPs, thereby enhancing the elasticity of the CU-CP. Figure 2B It is a schematic diagram of the distribution of the radio access protocol stack. As Figure 2B shown, for the user plane and the control plane, the radio access protocol stack can both be RLC, MAC, and PHY in the DU, and PDCP and above protocol layers in the CU.

[0102] It should be noted that: in the architectures shown in the above Figure 2A and Figure 2B 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 without parsing it and then transparently transmit it to the terminal or the CU. In the following embodiments, if such signaling transmission between the DU and the terminal is involved, at this time, the sending or receiving of the signaling by the DU includes this scenario. For example, the signaling of the RRC or PDCP layer will ultimately be processed into physical layer data and sent to the terminal, or transformed from the received physical layer data. In 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.

[0103] 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, and in addition to the access network devices and terminals, the above communication system may also include other devices or network elements, such as core network devices, relay devices, etc., and the embodiments of the present application also do not limit this.

[0104] First, the relevant terms involved in the embodiments of the present application will be explained below. It should be noted that these explanations are for making the embodiments of the present application easier to understand, and should not be regarded as a limitation on the protection scope required by the present application.

[0105] (1) Cell handover

[0106] Cell handover can be divided into two types. One is the cell handover implemented based on Layer 1 / Layer 2, which can be called Layer 1 / Layer 2 handover or Layer 1 / Layer 2 triggered mobility (LTM). The other is the cell handover implemented 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 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 layer of the protocol stack than the RRC layer (Layer 3), Layer 1 / Layer 2 handover can also be called lower layer handover, or bottom layer handover, or lower layer handover. This application does not limit the name of the specific handover technology.

[0107] For Layer 3 handover, in the CU-DU split architecture, the CU receives the measurement results of the terminal (the measurement results are forwarded to the CU by the DU), and determines whether to initiate a handover based on the measurement results. If it is determined to initiate a handover, the handover command is sent to the DU, and then sent to the terminal by the DU. Since this process involves communication interaction between the CU and the DU (i.e., the interaction of the F1 interface), and the maximum transmission delay of the F1 interface is about 3ms to 10ms, it will cause a certain handover delay.

[0108] For Layer 1 / Layer 2 handover, the handover decision is sent from the CU to the DU. That is, the DU determines whether to initiate a handover (LTM cell switch) based on the measurement results of the terminal, and directly sends the handover command message to the terminal, thereby effectively reducing F1 interaction and reducing handover delay.

[0109] (2) Scenarios of cell handover

[0110] When the terminal switches between different cells, there may be various specific handover scenarios. For example, the handover scenarios can be divided according to the location relationship between the source cell and the target cell.

[0111] Among them, when the access network device adopts the CU-DU split architecture (for example, the access network device includes a CU and multiple DUs, and multiple DUs are centrally controlled by a CU, and each of the multiple DUs can include one or more cells), 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 CU and / or the same DU. Among them, "a DU includes one or more cells" can also be described as "a DU manages or controls one or more cells", or "one or more cells of a DU", or "one or more cells belong to a DU". Here, three possible handover scenarios are described, namely Scenario 1 to Scenario 3.

[0112] Scenario 1: The terminal switches from one cell of a DU to another cell of the same DU. That is to say, the source cell and the target cell of the terminal belong to the same DU. The cell handover corresponding to Scenario 1 is an intra-DU handover.

[0113] Scenario 2: The terminal switches from one cell of DU1 controlled by a CU to one cell of DU2 controlled by the same CU. At this time, DU1 can be called the source DU, and DU2 can be called the target DU. That is to say, the source cell and the target cell of the terminal belong to different DUs controlled by the same CU. The cell handover corresponding to Scenario 2 is an inter-DU handover.

[0114] Scenario 3: The terminal switches from one cell of DU1 controlled by CU1 to one cell of DU3 controlled by CU2. At this time, CU1 can be called the source CU, and CU2 can be called the target CU. That is to say, the source cell and the target cell of the terminal belong to different DUs controlled by different CUs. The cell handover corresponding to Scenario 2 is an inter-CU handover.

[0115] When considering the access network device as a whole (such as a gNB), the positional 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, namely Scenario 4 and Scenario 5.

[0116] Scenario 4: The terminal switches from one cell of access network device 1 to one cell of access network device 2. At this time, access network device 1 can be called the source access network device, and access network device 2 can be called the target access network device. That is to say, the source cell and the target cell of the terminal belong to different access network devices. The cell handover corresponding to Scenario 4 is an inter-gNB handover.

[0117] Scenario 5: The terminal switches from one cell of an access network device to another cell of the same access network device. That is to say, the source cell and the target cell of the terminal belong to the same access network device. The cell handover corresponding to Scenario 5 is an intra-gNB handover.

[0118] The communication method provided by the embodiments of this application can be applied to any of the above scenarios.

[0119] (3) Downlink synchronization

[0120] Downlink timing is used for the terminal to perform downlink synchronization with the access network device. Downlink timing can be a cell-level parameter, and each cell has a corresponding downlink timing. The definition of downlink timing is the time when the first path (in time) of the corresponding downlink frame used by the terminal to determine the downlink timing is received from the reference cell at the UE antenna, and specific details can refer to existing protocols.

[0121] Taking the 5G communication system as an example, the uplink and downlink transmissions can use time slots as the basic time unit, that is, data is transmitted once within 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 and reaches the terminal side, and there will be a 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.

[0122] Here, the downlink timing difference involved in the following text is explained: as Figure 3A shown, the downlink reference signal 1 sent by DU1 at the downlink time slot boundary of cell A reaches the terminal after Tp1. The terminal determines the downlink time slot boundary 1 based on the received downlink reference signal 1. There is a time difference of Tp1 between the downlink time slot boundary of cell A and the downlink time slot boundary 1 determined by the terminal; the downlink reference signal 2 sent by DU2 at the downlink time slot boundary of cell B reaches the terminal after Tp2. The terminal determines the downlink time slot boundary 2 based on the received downlink reference signal 2. There is a time difference of Tp2 between the downlink time slot boundary of cell B and the downlink time slot boundary 2 determined by the terminal. Then the time difference between the downlink time slot boundary (such as downlink time slot boundary 1) determined by the terminal for cell A and the downlink time slot boundary (such as downlink time slot boundary 2) determined by the terminal for cell B is the downlink timing difference between cell A and cell B. It can be understood that the downlink time slot boundary can also be replaced by the downlink frame boundary.

[0123] (4) Uplink synchronization

[0124] Timing advance (TA) is used for uplink synchronization between the terminal and the access network device; 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 to which cell A belongs.

[0125] For cell handover, the terminal can obtain the TA of the target cell by sending a random access preamble. The following describes two possible methods, namely method 1 and method 2.

[0126] Method 1: Based on random access

[0127] Before the terminal performs cell handover (or before receiving the handover command), it can send random access preambles to the candidate DU on one or more candidate cells. For example, if one or more candidate cells include Cell A, the terminal can send random access preambles to DU1 belonging to Cell A on Cell A, and then DU1 can measure the TA of Cell A and send the TA of Cell A to the target DU (such as DU2) of the terminal. Subsequently, if DU2 decides to hand over the terminal to Cell A, it can send the TA of Cell A to the terminal through the handover command. Then, the terminal can obtain the TA of Cell A and, after handing over to Cell A, communicate according to the TA of Cell A.

[0128] Method 2: Method based on TA measurement or method based on the terminal measuring the downlink reference signal

[0129] 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; then, the terminal can determine the TA of Cell A or Cell B according to the downlink timing difference between Cell A and Cell B.

[0130] Taking the target cell as Cell A as an example, if the downlink slot boundaries of Cell A and Cell B (Cell B can be the source cell of the terminal) are synchronized, as Figure 3B shown, then determining the TA of Cell A based on the downlink timing difference can be achieved through the following formula 1:

[0131] TA_targetcell = TA_sourcecell + 2 * (Tnew - Told)...... Formula 1

[0132] 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.

[0133] The above formula 1 can also be transformed into:

[0134] TA_targetcell = TA_sourcecell - 2 * (Told - Tnew)

[0135] If the downlink slot boundaries of Cell A and Cell B (Cell B can be the source cell of the terminal) are not synchronized, then determining the TA of Cell A based on the downlink timing difference can be achieved through the following formula 2:

[0136] TA_targetcell = TA_sourcecell + 2 * (Tnew - Told) + offset...... Formula 2

[0137] Among them, offset represents the downlink time slot boundary deviation between cell A and cell B.

[0138] 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 can be indicated by the access network device to the terminal, and the specific implementation is not limited.

[0139] (5) Multi-TRP transmission technology

[0140] The multi-TRP transmission technology means that multiple TRPs provide services for the same terminal, thereby improving the data transmission efficiency of the terminal. 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 perform data transmission 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).

[0141] See Figure 4A and Figure 4B As shown, it is an example of two possible implementation methods of the multi-TRP transmission technology. Among them, Figure 4A The method shown is based on the multi-downlink control information (DCI) method. The DCI is carried on the physical downlink control channel (PDCCH), that is, each of the 2 TRPs transmits 1 DCI, and each DCI schedules 1 PUSCH or PDSCH. Figure 4B The method shown is based on the single-DCI method, that is, only 1 of the 2 TRPs transmits DCI, and this DCI can schedule 1 PUSCH or PDSCH; taking the example that this DCI schedules 1 PDSCH, a part of the stream / layer (corresponding to part of the demodulation reference signal (DMRS) ports) in this PDSCH is transmitted by one TRP, and the other part of the stream / layer (corresponding to part of the DMRS ports) is transmitted by the other TRP.

[0142] After introducing the multi-TRP transmission technology, before the terminal performs data transmission on a cell, it needs to synchronize with the TRP of that cell (such as uplink synchronization). Since different TRPs of the same cell are usually deployed at 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.

[0143] In the cell handover scenario, assume that the target cell for handover includes 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, it may cause the data transmission of the terminal on the target cell to fail (for example, if the TA of the target cell obtained by the terminal is the TA for TRP1, but the terminal uses this TA to send data to TRP2, it will cause the data transmission to fail), that is, effective data transmission cannot be performed, affecting the efficiency of data transmission.

[0144] Based on this, in the embodiments of the present application, the relevant implementation of the multi-TRP transmission technology in the cell handover scenario will be studied. Exemplarily, the embodiments of the present application provide a communication method for the terminal to obtain the correspondence between the TA and TAG of the target cell in the cell handover scenario, facilitating the terminal to quickly perform effective data transmission on the target cell and improving the efficiency of data transmission.

[0145] Among them, the communication method provided in the embodiments of the present application involves at least one network device and a terminal. Below, in combination with some handover scenarios described above, the network devices involved in the embodiments of the present application will be described:

[0146] (1) In the same-DU handover (Scenario 1), the network devices involved in the embodiments of the present application include the CU and the DU managed by the CU. The source cell and the candidate cell of the terminal both belong to this DU.

[0147] (2) In the cross-DU handover (Scenario 2), the network devices involved in the embodiments of the present application include the CU, the first DU managed by the CU (i.e., the source DU of the terminal), and the second DU managed by the CU (i.e., the candidate DU of the terminal). Among them, the first DU, the second DU, and the CU may belong to the same access network device (such as gNB). In the embodiments of the present application, if the terminal hands over to the cell managed by the candidate DU, the candidate DU can also be called the target DU, and other similar situations (such as candidate cells, candidate access network devices) can be processed with reference.

[0148] (3) In the cross-CU handover (Scenario 3), the network devices involved in the embodiments of the present application include the first CU, the first DU managed by the first CU (i.e., the source DU of the terminal), the second CU, and the second DU managed by the second CU (i.e., the candidate DU of the terminal).

[0149] (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).

[0150] (5) In same-site handover (Scenario 5), the network device involved in the embodiments of the present application is an access network device (such as a g-NB), and both the source access network device and the candidate access network device of the terminal are this access network device.

[0151] The communication method provided by the embodiments of the present application will be described in detail below in combination with Embodiments 1 to 3. Without special explanation, "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.

[0152] Embodiment 1

[0153] In Embodiment 1, the interaction among a first network device, a second network device, and a terminal will be used as an example for description.

[0154] Among them, for scenario 1: The first network device and the second network device can be the same DU. In this case, the related operations of interaction between the first network device and the second network device can be not executed. For scenario 2: The first network device can be the first DU (i.e., the source DU), and the second network device can be the second DU (i.e., the candidate DU). The first network device and the second network device perform relay communication through the CU, that is, the first DU -> CU -> the second DU, or the second DU -> CU -> the first DU. For relay communication, the information transmitted between different nodes is the same, and the message names carrying these information can be the same or different, which is not limited. For example, the specific implementation of "the second network device sends the third message to the first network device" is: The second network device sends the third message a to the CU. After receiving the third message a, the CU sends the third message b to the first network device. The information carried by the third message a and the third message b is the same, 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 to send the corresponding message to the second network device, that is, through the CU relay. For scenario 3: The first network device can be the first DU managed by the first CU, and the second network device can be the second DU managed by the second CU. The first network device and the second network device perform relay communication through the first CU and the second CU, that is, the first DU -> the first CU -> the second CU -> the second DU, or the second DU -> the second CU -> the first CU -> the first DU. For scenario 4: The first network device can be the first access network device, and the second network device can be the second access network device. 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 related operations of interaction between the first network device and the second network device can be not executed.

[0155] Figure 5 It is the schematic flow diagram corresponding to the communication method provided in the first embodiment of this application. As Figure 5 shown, the method includes:

[0156] S501, The second network device sends a third message to the first network device, and the third message is used to indicate that the first TAG among multiple TAGs corresponds to the first information; correspondingly, the first network device receives the third message.

[0157] Here, multiple TAGs (i.e., N TAGs) correspond to the same cell, namely 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. The multiple TAGs can be allocated by the second network device for the terminal for the first cell, and the multiple TAGs correspond one-to-one with multiple TRPs corresponding to the first cell. For example, taking the first cell as an example, the first cell corresponds to M TRPs, the first cell corresponds to N TAGs (i.e., the second network device allocates N TAGs for the terminal for the first cell), and the N TAGs correspond one-to-one with N of the M TRPs. Both M and N are integers greater than 1, and M is greater than or equal to N.

[0158] In a 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. Among them, 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.

[0159] Among them, the first information is used to indicate at least one of the following: the first TRP; the first synchronization signal block (SSB); the first random access resource; the first TAG. The first information can uniquely identify the first TAG from the network side (e.g., the second network device). Similar to the first information, the second information is used to indicate at least one of the following: the second TRP; the identification information of the second SSB; the second random access resource; the second TAG. The second information can uniquely identify the second TAG from the network side (e.g., the second network device). Three possible examples of the first information are described below with reference to Example 1 to Example 3, and the second information can be processed by reference.

[0160] Example 1: The first information includes the identification information of the first TRP. For example, the identification information of the first TRP can be a newly introduced information used to uniquely identify the first TRP. The identification information of the first TRP can be allocated by the second network device.

[0161] 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 resources 1 and 2, SSB2 corresponds to random access resources 3 and 4; the second TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resources 1 and 2, SSB2 corresponds to random access resources 3 and 4. A random access resource shown in the embodiments of the present application is a resource for one random access attempt. For example, random access resource 1 is a resource for one random access attempt, and random access resource 2 is a resource for one random access attempt.

[0162] Table 1: Example of SSBs and random access resources corresponding to the first TRP and the second TRP

[0163]

[0164] Example 2: The first information includes the identification information of the first SSB corresponding to the first TRP. For example, the first TRP corresponds to a set of SSBs, and this set of SSBs includes one or more SSBs. Here, the first SSB can be this set of SSBs, or the first SSB is one of the SSBs in this set of SSBs.

[0165] This example can be applicable to scenarios where the SSBs corresponding to the first TRP and other TRPs (such as the second TRP) are different. For example, as shown in Table 2, the first TRP corresponds to SSB1 and SSB2, SSB1 corresponds to random access resources 1 and 2, SSB2 corresponds to random access resources 3 and 4; the second TRP corresponds to SSB3 and SSB4, SSB3 corresponds to random access resources 1 and 2, SSB4 corresponds to random access resources 3 and 4.

[0166] Table 2: Example of SSBs and random access resources corresponding to the first TRP and the second TRP

[0167]

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

[0169] Example 3: The first information includes the 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 the information of the first random access resource. Referring to the description of Information 1 in the following text, or for another example, the identification information of the first random access resource is the configuration identifier of the first random access resource.

[0170] For example, the first TRP corresponds to a random access resource set, and the random access resource set 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 can also be a random access resource in the random access resource set.

[0171] This example can be applicable to the scenario where the random access resources corresponding to the first TRP and other TRPs (such as the second TRP) are different. For example, as shown in Table 3, 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 5 and random access resource 6, and SSB2 corresponds to random access resource 7 and random access resource 8.

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

[0173]

[0174] In addition, after receiving the third message, the first network device can store the corresponding relationship between the first TAG and the first information, so as to facilitate subsequent determination of the TA corresponding to the first TAG.

[0175] S502, the second network device sends a first message to the first network device, and the first message includes the first TA information of the first cell; correspondingly, the first network device receives the first message from the second network device.

[0176] Exemplarily, the second network device can 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 a possible way is described here:

[0177] The second network device sends the 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 on random access resources (for ease of description, referred to as Information 1). For example, the random access resources include the time-frequency resources 1 for random access and the first preamble. Information 1 includes information for indicating the time-frequency resources 1 and / or the identification information of the first preamble. Optionally, it further includes the configuration identification of the random access resources (the configuration identification corresponds to the identification information of the first cell).

[0178] The first network device obtains the location information of the terminal (for example, obtains the location information of the terminal according to the RSRP information of the first cell). According to the location information of the terminal, it is determined that the terminal may subsequently move into the coverage area of the first cell. The first network device determines that the time-frequency resources 1 for random access and the first preamble correspond to the terminal (referred to as correspondence a), and sends indication information to the terminal. The indication information may be a physical downlink control channel (PDCCH) order. The indication information is used to instruct the terminal to send a random access preamble (i.e., the first preamble) using the time-frequency resources 1 for random access on the first cell. For example, the indication information includes the identification information of SSB1 and the index value of the time-frequency resources 1 for random access corresponding to SSB1, and also includes the identification information of the first preamble. Among them, the random access resources corresponding to SSB1 include multiple periodically occurring time-frequency resources for random access, and the index value of the time-frequency resources 1 for random access is used to indicate that the time-frequency resources 1 for random access are one of these multiple time-frequency resources for random access.

[0179] Accordingly, after receiving the indication information, the terminal can send a random access preamble (i.e., the first preamble) according to the time-frequency resources 1 for random access. Furthermore, the second network device determines the first TA information based on the random access preamble, and determines that the above first information corresponds to the first TA information. Specifically, after receiving the random access preamble through the first TRP, the second network device 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 random access preamble, the second network device determines the second TA information and determines that the above second information corresponds to the second TA information. Specifically, after receiving the random access preamble through the second TRP, the second network device determines the second TA information and determines that the second TA information corresponds to the second TRP. In this case, the first message further includes the second TA information.

[0180] In addition, the above first message further includes the above first information.

[0181] The above first message may further include information on the random access resources corresponding to the first TA information (for ease of description, referred to as "information 1'"), where information 1' includes the RA-RNTI corresponding to the time-frequency resource 1 for random access (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 a random access preamble on the time-frequency resource 1 for random access and determines the first TA information. Among them, the RA-RNTI corresponding to the time-frequency resource 1 for random access (i.e., the first RA-RNTI) is determined according to the time-frequency resource 1 for random access. Further, after receiving the first message, the first network device can determine that the first TA information corresponds to the terminal according to the first RA-RNTI, the identification information of the first preamble, and the above corresponding relationship a.

[0182] S503, the first network device determines that the first TA information corresponds to the first TAG.

[0183] 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 methods are described here.

[0184] Implementation method 1:

[0185] 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 according to the first message and the third message. Specifically, the first network device determines that the first TA information corresponds to the first TAG according to the "corresponding relationship between the first TAG and the first information" indicated by the third message and the "corresponding relationship between the first TA information and the first information" indicated by the first message.

[0186] Optionally, the first message further includes the second TA information and the second information corresponding to the second TA information. Further, the first network device determines that the second TA information corresponds to the second TAG according to the "corresponding relationship between the second TAG and the second information" indicated by the third message and the "corresponding relationship between the second TA information and the second information" indicated by the first message.

[0187] Implementation method 2:

[0188] When the first message includes the first TA information, it is assumed that the first TRP and the second TRP correspond to different SSBs or different random access resources. After the first TRP of the first cell receives the first preamble in the time-frequency resource 1 for random access, the second network device can determine the first TA information of the first cell. Since the time-frequency resource 1 for random access corresponds to the first TRP, even if the second TRP of the first cell receives the first preamble in the time-frequency resource 1 for random access, 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 time-frequency resource 1 for random access, it does not send the second TA information to the first network device. That is to say, the first message includes the first TA information and does not include other TA information (such as not including the second TA information).

[0189] In this case, the first network device determines, based on the first message and the third message (and the PDCCH order), that the first TA information corresponds to the first TAG. Different from the above implementation manner 1, the first message does not include the first information corresponding to the first TA information.

[0190] 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 according to the information 1’ carried in the first message; furthermore, the first network device determines, based on the identification information of SSB1 in the previously sent PDCCH order and the corresponding relationship between the first TAG and the first SSB indicated by the third message, that the first TA information corresponds to the first TAG.

[0191] For another example, when the first information is used to indicate the first random access resource (such as the time-frequency resource 1 for random access and the first preamble), after receiving the first message, the first network device determines that the first TA information corresponds to the first random access resource according to the information 1’ carried in the first message, and then determines, based on the corresponding relationship between the first random access resource and the first TAG indicated by the third message, that the first TA information corresponds to the first TAG.

[0192] For another example, when 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 according to the information 1’ carried in the first message; furthermore, 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 corresponding relationship between the first TRP and the first SSB (this corresponding relationship can be sent by the second network device to the first network device, such as through the third message), and determines, based on the corresponding relationship between the first TAG and the first TRP, that the first TA information corresponds to the first TAG.

[0193] For the manner in which the first network device determines the second TA information corresponding to the second TAG, refer to the above two implementation manners.

[0194] S504. The first network device sends a second message to the terminal. The second message includes the identification information of the target cell for handover, the first TA information, and the identification information of the first TAG corresponding to the first TA information. The target cell is the first cell. Correspondingly, the terminal receives the second message.

[0195] Exemplarily, the second message is a handover command message and can be transmitted through a medium access control (MAC) control element (CE). The first TA information is included in the second message, and the first TA information is further used to instruct the terminal to access the target cell in a random access free or RACH-less manner.

[0196] 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 the identification information of the second TAG corresponding to the second TA information.

[0197] 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 (only identifies the first TAG under this terminal and needs to correspond to a certain terminal), which is different from the first information (identifies the first TAG under the cell and may not need to correspond to a certain terminal).

[0198] S505. The terminal determines, according to the second message, that the first TA information corresponds to the first TAG, and accesses the target cell using the TA indicated by the first TA information.

[0199] Specifically, the terminal uses the TA indicated by the first TA information to access the target cell in a RACH-less manner.

[0200] Exemplarily, the second network device may allocate uplink resources for the terminal (for example, the uplink resources correspond to the first TAG). Further, the terminal may use the TA indicated by the first TA information to send uplink information to the second network device on the uplink resources. Correspondingly, after receiving the uplink information, the second network device may determine that the terminal has successfully accessed the target cell.

[0201] 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, it starts the timer corresponding to the first TAG (i.e., the first timing advance timer). Among them, during the operation of the first timing advance timer, it can be considered that the first TAG of the terminal and the target cell are uplink synchronized. 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.

[0202] 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, it starts the timer corresponding to the second TAG (i.e., the second timing advance timer). Among them, during the operation of the second timing advance timer, it can be considered that the second TAG of the terminal and the target cell are uplink synchronized.

[0203] Among them, the duration of the first timing advance timer and / or the duration of the second timing advance timer are provided by the second network device to the terminal, for example, sent to the terminal through relay communication.

[0204] S506. The second network device determines that the terminal has obtained the TA corresponding to the first TAG.

[0205] 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. Or, after the terminal successfully accesses the target cell, that is, the first cell, it sends the first indication information to the second network device, and the first indication information 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. Or, the first network device sends the first indication information to the second network device, for example, after the first network device sends the second message to the terminal, it sends the first indication information to the second network device. Therefore, the second network device can determine that the terminal has obtained the TA corresponding to the first TAG.

[0206] Optionally, the second network device may also determine that the terminal has obtained the TA corresponding to the second TAG. For example, after the terminal accesses the first cell, it sends second indication information to the second network device, and 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 second indication information to the second network device. For example, after the first network device sends a second message to the terminal, it sends second indication information to the second network device.

[0207] The above first indication information and second indication information may be different information (for example, the first indication information includes the identification information of the first TAG, and the second indication information includes the identification information of the second TAG), or may also be the same information (for example, it is indicated by one bit that the TAs corresponding to the first TAG and the second TAG have 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, and no specific limitation is made.

[0208] Optionally, the above method further includes:

[0209] S507, the second network device sends downlink control information to the terminal, and the downlink control information is used to indicate uplink resources or downlink resources; correspondingly, 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 handover is completed.

[0210] Exemplarily, taking the downlink control information of the first TAG as an example, after the second network device determines that the terminal has obtained the TA corresponding to the first TAG, it schedules the terminal to perform data transmission of the first TAG. For example, it sends downlink control information to the terminal, and 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 obtained the TA corresponding to the first TAG, it does not schedule the terminal to perform data transmission of the first TAG, or first instructs the terminal to perform uplink synchronization to obtain the TA corresponding to the first TAG.

[0211] Optionally, when the downlink control information or the resources indicated by the downlink control information correspond to a non-first TAG (for example, the second TAG), the terminal cannot determine that the handover is completed (that is, the RACH-less handover is completed). It should be particularly noted that beam 1 (that is, the transmission configuration indication state (TCIstate)) corresponds to the first TAG, and this corresponding relationship is pre-configured by the second network device for the terminal. Based on beam 1, the terminal receives the downlink control information and can determine that the downlink control information corresponds to the first TAG.

[0212] For example, in the foregoingFigure 4A In the scenario shown, it is assumed that the target cell (i.e., the first cell) corresponds to a first TAG and a second TAG. Therefore, the second network device can send downlink control information 1 and / or downlink control information 2 to the terminal. 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 completed only when it receives downlink control information 1; if the terminal receives downlink control information 2, it is not certain that the handover is completed.

[0213] For another example, in the scenario Figure 4B shown above, it is assumed that the target cell (i.e., the first cell) corresponds to a first TAG and a second TAG. Therefore, the second network device can send downlink control information 3 to the terminal, and 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, when downlink control information 3 is used to indicate the resources corresponding to the first TAG, the terminal can determine that the handover is completed; if downlink control information 3 is used to indicate the resources corresponding to the second TAG, the terminal is not certain that the handover is completed.

[0214] By adopting 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 is convenient for the terminal to quickly perform effective data transmission on the target cell and improve the efficiency of data transmission.

[0215] Embodiment 2

[0216] In Embodiment 2, based on Embodiment 1, taking Scenario 2 as an example, a possible implementation process will be described.

[0217] Figure 6 It is a schematic flowchart corresponding to the communication method provided in Embodiment 2 of this application. As Figure 6 shown, the method includes:

[0218] S601, the CU sends Message 1 to the second DU, and Message 1 is used to request LTM configuration.

[0219] Exemplarily, Message 1 may include request information, and the request information is used to request the random access configuration of multiple TAGs.

[0220] Among them, there can be various 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, specifically including the measurement results of neighboring cells. A neighboring cell refers to a cell that the terminal may switch to after moving. Further, 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. Correspondingly, 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.

[0221] S602. The second DU sends Message 2 (i.e., the third message a) to the CU, and Message 2 includes the LTM configuration information of the first cell. Correspondingly, the CU receives Message 2.

[0222] Here, the LTM configuration information of the first cell includes the lower-layer RRC configuration, reference signal configuration, transmission configuration indication status configuration, and random access channel configuration of the first cell.

[0223] Furthermore, when Message 1 includes request information, Message 2 further includes the first correspondence information of the first cell. The first correspondence information includes the identification information of the first TAG and the first information corresponding to the first TAG. Optionally, Message 2 further includes one or more other correspondence information of the first cell (such as further including the second correspondence information of the first cell). The second correspondence information includes the identification information of the second TAG and the second information corresponding to the second TAG. Among them, 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) is sent based on the request of the request information.

[0224] In other examples, Message 1 may not include request information. In this case, the second DU actively sends the first correspondence information (and the second correspondence information).

[0225] The above Message 1 may be a UE context setup request message, and Message 2 may be a UE context modification response message.

[0226] S603. The CU sends Message 3 (i.e., the third message b) to the first DU. Correspondingly, the first DU receives Message 3.

[0227] Here, message 3 may include the first correspondence information of the first cell. Optionally, it may also include the second correspondence information of the first cell. Optionally, message 3 further 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.

[0228] S604, the first DU sends message 4 to the CU; correspondingly, the CU receives message 4.

[0229] Exemplarily, message 4 may include the channel state information (CSI) resource configuration of the source cell, and this CSI resource configuration is used for the terminal to send the 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.

[0230] The above message 3 may be a UE context modification request message, and message 4 may be a UE context modification response message.

[0231] Optionally, the CU may also send a UE context modification request message to the second DU. The UE context modification request message may include: the identification information of the source cell and the RS configuration of the source cell. Correspondingly, the second DU sends a UE context modification response message to the CU. The UE context modification response message may include: the CSI resource configuration generated by the second DU, and this CSI resource configuration is used for 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 source cell becomes the candidate cell.

[0232] S605, the CU sends an RRC reconfiguration message to the terminal; correspondingly, the terminal receives the RRC reconfiguration message.

[0233] 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, and the DL RRC message includes the RRC reconfiguration message; correspondingly, after receiving the DL RRC message, the first DU sends the RRC reconfiguration message to the terminal.

[0234] Among them, the RRC reconfiguration message may include the LTM configuration information of the first cell. Optionally, it may also include 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 allocates uplink resources for the terminal for the first cell (such as this uplink resource corresponds to the first TAG).

[0235] S606, The terminal sends an RRC reconfiguration complete message to the CU; correspondingly, the CU receives the RRC reconfiguration complete message.

[0236] Here, after receiving the RRC reconfiguration message, the terminal may send an uplink (UL) RRC message to the first DU, and the UL RRC message includes the RRC reconfiguration complete message; furthermore, the first DU may forward the RRC reconfiguration complete message to the CU.

[0237] S607, The first DU sends a PDCCH order to the terminal, and the PDCCH order is used to instruct the terminal to send a random access preamble on the first cell; correspondingly, the terminal receives the PDCCH order.

[0238] S608, The terminal sends a random access preamble on the first cell according to the PDCCH order; correspondingly, the second DU receives the random access preamble.

[0239] S609, The second DU determines the first TA information according to the random access preamble, and sends message 5 (i.e., the first message a) to the CU, and message 5 includes the first TA information and the first information corresponding to the first TA information.

[0240] S610, The CU sends message 6 (i.e., the first message b) to the first DU, and message 6 includes the first TA information and the first information corresponding to the first TA information.

[0241] S611, The first DU determines that the first TA information corresponds to the first TAG.

[0242] It can be understood that the terminal may also perform downlink synchronization with the first cell. For example, the first DU sends an activation indication of the TCI state 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 according to the activation indication of the first cell.

[0243] S612, The terminal sends a measurement report to the first DU, and the measurement report includes the downlink measurement results of multiple candidate cells.

[0244] For example, the terminal may measure the RS of multiple candidate cells according to the RS configuration of the multiple candidate cells to obtain the downlink measurement results of the multiple candidate cells, and send the downlink measurement results of the multiple candidate cells to the first DU according to the CSI resource configuration of the source cell.

[0245] S613, The first DU sends a handover command message (i.e., the second message) to the terminal, and the handover command message is used to instruct the terminal to hand over to the first cell.

[0246] S614. The terminal determines, according to the handover command message, that the first TA information corresponds to the first TAG, and accesses the target cell using the TA indicated by the first TA information.

[0247] Exemplarily, if the first DU determines to hand over the terminal to the first cell according to the downlink measurement results of multiple candidate cells, it sends a handover command message to the terminal. The handover command message includes the identification information of the target cell of the handover, the first TA information, and the first information corresponding to the first TA information. Correspondingly, the terminal accesses the first cell using the TA indicated by the first TA information, for example, accesses the first cell through PUSCH (i.e., without random access).

[0248] S615. 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. Correspondingly, the CU receives the LTM cell change notification message.

[0249] Here, the LTM cell change notification message includes the identification information of the target cell.

[0250] Optionally, the LTM cell change notification message further includes the first indication information and / or the second indication information.

[0251] 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.

[0252] S617. The second DU determines that the terminal has obtained the TA corresponding to the first TAG.

[0253] S618. The second DU sends downlink control information to the terminal. The downlink control information is used to indicate uplink resources or downlink resources. Correspondingly, the terminal receives the downlink control information. When the downlink control information or the resources indicated by the downlink control information correspond to the first TAG, the terminal determines that the handover is completed.

[0254] 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 indicate the release of the resources of the candidate cell of the source DU. Further, 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 completion message to the CU.

[0255] It can be understood that Figure 6 the process shown Figure 5It corresponds to the flowchart shown, and the steps of the two can be referred to each other. For example, S602 and S603 correspond to S501 in the first embodiment, S609 and S610 correspond to S502 in the first embodiment, S611 corresponds to S503 in the first embodiment, S613 corresponds to S504 in the first embodiment, S614 corresponds to S505 in the first embodiment, S617 corresponds to S506 in the first embodiment, and S618 corresponds to S507 in the first embodiment.

[0256] Embodiment 3

[0257] In Embodiment 3, the interaction between the first network device, the second network device, and the terminal will be described as an example. Among them, the first network device and the second network device can refer to the description in the first embodiment.

[0258] Figure 7 It is a flowchart corresponding to the communication method provided in Embodiment 3 of this application. As Figure 7 shown, the method includes:

[0259] S701, the second network device sends a fourth message to the terminal, and the fourth message is used to indicate that random access corresponds to the first TAG; correspondingly, the terminal receives the fourth message. A possible implementation is that 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 can send the fourth message to the terminal through relay communication.

[0260] The above S701 can also be replaced by S701'. S701', the first network device sends a fourth message to the terminal, and the fourth message is used to indicate that random access corresponds to the first TAG; correspondingly, the terminal receives the fourth message. A possible implementation is that the fourth message is a handover command message. Among them, the second network device can indicate to the first network device that random access corresponds to the first TAG, and then the first network device uses the handover command message to indicate to the terminal that random access corresponds to the first TAG.

[0261] 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 for the terminal for the first cell). For example, the multiple TAGs include the first TAG and the second TAG, 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. The first TRP and the second TRP correspond to different random access resources.

[0262] Exemplarily, the fourth message includes correspondence information (which may be referred to as the third correspondence information), and the third correspondence information is used to indicate that 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 the identification information of the first TAG, and the identification information of the first TAG is used to indicate that random access corresponds to the first TAG.

[0263] Exemplarily, the fourth message is an RRC reconfiguration message, and 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.

[0264] S702, the terminal obtains the first TA information according to random access.

[0265] Exemplarily, the second network device may send the random access channel configuration of the first cell to the first network device, where the random access channel configuration may include information on random access resources, and the random access resources are the random access resources corresponding to the first TAG (or the first TRP). For example, the random access resources include the time-frequency resources 1 for random access and the first preamble. Among them, the first network device is the network device to which the source cell of the terminal belongs.

[0266] The first network device obtains the location information of the terminal. According to the location information of the terminal, if it is determined that the terminal may move to the coverage area of the first cell in the future, an indication information is sent to the terminal, and 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., the first preamble) using the time-frequency resources 1 for random access on the first cell. For example, the indication information includes the identification information of SSB1 and the index value of the time-frequency resources 1 for random access corresponding to SSB1, and also includes the first preamble.

[0267] Correspondingly, after receiving the indication information, the terminal may send a random access preamble (i.e., the first preamble) on the first cell according to the time-frequency resources 1 for random access. 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 sends the first TA information to the first network device. It can be understood that since the time-frequency resources 1 for random access correspond to the first TRP, even if the second TRP of the first cell receives the random access preamble on the time-frequency resources 1 for random access, the second network device does not 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 according to the random access preamble received on the time-frequency resources 1 for random access, it does not send the second TA information to the first network device.

[0268] Subsequently, if the first network device determines to switch the terminal to the first cell, it sends a handover command message to the terminal. The handover command message includes the identification information of the target cell for handover and the first TA information, and the first TA information is carried in the TA field in the handover command message. Here, the target cell is the first cell, that is, this handover command message is a handover command message for the first cell. Furthermore, the terminal can obtain the first TA information from the handover command message.

[0269] S703. The terminal determines, according to the fourth message, that the first TA information corresponds to the first TAG.

[0270] Here, the terminal determines, according to 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.

[0271] S704. The second network device determines that the terminal has obtained the TA corresponding to the first TAG according to random access.

[0272] Optionally, the above method further includes:

[0273] S705. The second network device sends downlink control information to the terminal, and the downlink control information is used to indicate uplink resources or downlink resources; correspondingly, 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 handover is completed.

[0274] S704 and S705 above can refer to S506 and S507 in Embodiment 1.

[0275] By adopting the above method, the second network device indicates to the terminal that random access corresponds to the first TAG, so that after the terminal obtains the first TA information according to random access, it can determine that the first TA information corresponds to the first TAG, which is convenient for the terminal to quickly perform effective data transmission on the target cell and improves the efficiency of data transmission.

[0276] Embodiment 4

[0277] In Embodiment 4, based on Embodiment 3, taking Scenario 2 as an example, a possible implementation process will be described.

[0278] Figure 8 It is a schematic flowchart corresponding to the communication method provided in Embodiment 4 of this application. As Figure 8 shown, the method includes:

[0279] S801. The CU sends Message 1 to the second DU, and Message 1 is used to request LTM configuration.

[0280] Exemplarily, Message 1 may include request information for requesting the random access configuration of multiple TAGs.

[0281] S802. The second DU sends Message 2 to the CU, and Message 2 includes the LTM configuration information of the first cell; correspondingly, the CU receives Message 2.

[0282] Here, the LTM configuration information of the first cell includes the lower layer RRC configuration, reference signal configuration, transmission configuration indication status configuration, and random access channel configuration of the first cell.

[0283] Further, when Message 1 includes request information, Message 2 includes third correspondence information for indicating that the random access corresponds to the first TAG. Alternatively, Message 1 may not include request information, and in this case, the second DU actively sends the third correspondence information.

[0284] S803. The CU sends Message 3 to the first DU; correspondingly, the first DU receives Message 3.

[0285] Here, Message 3 includes the random access channel configuration of the first cell, where the random access configuration may include information on random access resources, and the random access resources are the random access resources corresponding to the first TAG (or the first TRP). Optionally, Message 3 further includes the reference signal configuration of the first cell, the TCI status configuration of the first cell, and the RACH configuration of the first cell.

[0286] S804. The first DU sends Message 4 to the CU; correspondingly, the CU receives Message 4.

[0287] Exemplarily, Message 4 may include the channel state information resource configuration of the source cell, and the CSI resource configuration is used for the terminal to send the 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.

[0288] Among them, the message names of Messages 1 to 4 may refer to the description in Embodiment 2.

[0289] S805. The CU sends an RRC reconfiguration message to the terminal; correspondingly, the terminal receives the RRC reconfiguration message.

[0290] Here, the RRC reconfiguration message includes the LTM configuration information of the first cell and further includes third correspondence information for indicating that the random access corresponds to the first TAG.

[0291] S806. The terminal sends an RRC reconfiguration complete message to the CU; correspondingly, the CU receives the RRC reconfiguration complete message.

[0292] S807, the first DU sends a PDCCH order to the terminal, and the PDCCH order is used to instruct the terminal to send a random access preamble on the first cell; correspondingly, the terminal receives the PDCCH order.

[0293] S808, the terminal sends a random access preamble on the first cell according to the PDCCH order; correspondingly, the second DU receives the random access preamble.

[0294] S809, the second DU determines the first TA information according to the random access preamble and sends a message 5 to the CU, and the message 5 includes the first TA information.

[0295] S810, the CU sends a message 6 to the first DU, and the message 6 includes the first TA information; correspondingly, the first DU receives the message 6 and obtains the first TA information.

[0296] S811, the terminal sends a measurement report to the first DU, and the measurement report includes the lower layer measurement results of multiple candidate cells.

[0297] S812, the first DU sends a handover command message to the terminal, and the handover command message is used to instruct the terminal to hand over to the first cell.

[0298] Among them, the handover command message includes the identification information of the target cell of the handover and the first TA information.

[0299] S813, the terminal determines 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.

[0300] Exemplarily, according to the random access indicated by the RRC reconfiguration message corresponding to the first TAG, the terminal can determine that the first TA information corresponds to the first TAG.

[0301] S814, the first DU sends a LTM cell change notification message to the CU, and the LTM cell change notification message is used to indicate that a cell handover command has been initiated for the terminal; correspondingly, the CU receives the LTM cell change notification message.

[0302] Here, the LTM cell change notification message includes the identification information of the target cell.

[0303] S815, the CU sends a LTM cell change notification message to the second DU; correspondingly, the second DU receives the LTM cell change notification message.

[0304] S816, the second DU determines that the terminal has obtained the TA corresponding to the first TAG.

[0305] S817, the second DU sends downlink control information to the terminal, and the downlink control information is used to indicate uplink resources or downlink resources; correspondingly, 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 handover is completed.

[0306] It can be understood that Figure 8 the process shown Figure 7 corresponds to the process shown, and the steps of the two can be referred to each other. For example, S801 to S805 correspond to S701 in the first embodiment, S807 to S812 correspond to S702 in the first embodiment, S813 corresponds to S703 in the first embodiment, S816 corresponds to S704 in the first embodiment, and S817 corresponds to S705 in the first embodiment.

[0307] Embodiment Five

[0308] In Embodiment Five, the interaction among the first network device, the second network device, and the terminal will be described as an example. Among them, the first network device and the second network device can refer to the description in the first embodiment.

[0309] Figure 9 is a schematic flow chart corresponding to the communication method provided in Embodiment Five of this application. As Figure 9 shown, the method includes:

[0310] S901, the second network device sends a fifth message to the terminal, and the fifth message is used to indicate that the first TA measurement corresponds to the first TAG; correspondingly, the terminal receives the fifth message. A possible implementation is that the fifth message can 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 can send the fifth message to the terminal through relay communication.

[0311] The above S901 can also be replaced by S901'. S901', the first network device sends a fifth message to the terminal, and the fifth message is used to indicate that the first TA measurement corresponds to the first TAG; correspondingly, the terminal receives the fifth message. A possible implementation is that the fifth message is a handover command message.

[0312] 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 for the terminal for the first cell). For example, the multiple TAGs include the first TAG and the second TAG. For example, the first TAG corresponds to the first TRP, the second TAG corresponds to the 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.

[0313] Optionally, the fifth message is further used to indicate that the second TA measurement corresponds to the second TAG.

[0314] Among them, "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, and the fourth correspondence information is used to indicate that the first TA measurement corresponds to the first TAG; among them, the fourth correspondence information may include the configuration information of the first reference signal (such as the identification information of the first reference signal), and the identification information of the first TAG corresponding to the first reference signal. Optionally, the fifth message further includes fifth correspondence information, and the fifth correspondence information is used to indicate that the second TA measurement corresponds to the second TAG; among them, the fifth correspondence information includes the configuration information of the second reference signal and the identification information of the second TAG corresponding to the second reference signal. In addition, the fifth message further includes the first measurement identification corresponding to the first reference signal and the second measurement identification 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 identification and the second measurement identification may be the same or different.

[0315] In a possible example, the fifth message includes a TAG identification (such as the first TAG identification or the second TAG identification), and then this TAG identification can also be used to indicate the TAG corresponding to the first TA measurement.

[0316] It should be noted that "the first TA measurement corresponds to the first TAG" can also be understood as that 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 that the TA determined by the terminal based on the second TA measurement corresponds to the second TAG.

[0317] In a possible example, in S901, the fifth message is an RRC reconfiguration message, and the RRC reconfiguration message 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.

[0318] 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 a 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.

[0319] 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 configuration information of the third reference signal of the source cell and a third measurement identifier corresponding to the third reference signal.

[0320] S902: The terminal obtains the first TA according to measurement of the first TA.

[0321] Exemplarily, the specific implementation of the terminal obtaining the first TA according to the first TA measurement may be: the terminal measures the first reference signal to obtain the first downlink timing; and measures 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 according to the first downlink timing, the third downlink timing and the TA of the source cell, specifically referring to Formula 1 or Formula 2 above.

[0322] Optionally, the terminal further obtains the second TA according to the second TA measurement. The specific implementation may be: the terminal measures the second reference signal to obtain the second downlink timing; and measures 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 according to the second downlink timing, the third downlink timing and the TA of the source cell, specifically referring to Formula 1 or Formula 2 above.

[0323] S903: The terminal determines, according to the fifth message, that the first TA corresponds to the first TAG.

[0324] 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.

[0325] In a possible implementation, the terminal determines that the first TA corresponds to the first TAG according to the correspondence between the first reference signal and the first TAG in the fifth message. Optionally, the terminal determines that the second TA corresponds to the second TAG according to the correspondence between the second reference signal and the second TAG in the fifth message.

[0326] 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.

[0327] S904, the second network device determines that the terminal has obtained the TA corresponding to the first TAG according to the first TA measurement.

[0328] Exemplarily, if the first network device determines to hand over the terminal to the first cell, it sends a handover command message to the terminal. The handover command message includes the identification information of the target cell of the handover, and the target cell is the first cell. Correspondingly, 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.

[0329] Exemplarily, the second network device may allocate uplink resources for the terminal (for example, the uplink resources correspond to the first TAG), and then the terminal may use the first TA to send uplink information to the second network device on the uplink resources; correspondingly, after receiving the uplink information, the second network device may 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 may 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. Or, the first network device sends a 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 a first indication message to the second network device. Exemplarily, there is a corresponding relationship b between TCI state 1 and the first TAG, and the first indication message may be the identification information of TCI state 1, and the identification information of this TCI state 1 is also indicated to the terminal in the handover command message, which 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 according to the identification information of TCI state 1 and the corresponding relationship b.

[0330] Optionally, the second network device may also determine that the terminal has obtained the TA corresponding to the second TAG. For example, after the terminal accesses the first cell, it 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. Or, the first network device sends a 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 a second indication message to the second network device. Exemplarily, there is a corresponding relationship c between TCI state 2 and the second TAG, and the first indication message may be the identification information of TCI state 2, and the identification information of this TCI state 2 is also indicated to the terminal in the handover command message, which 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 according to the identification information of TCI state 2 and the corresponding relationship c.

[0331] Exemplarily, when the terminal receives the second message and obtains the first TA according to the measurement of the first TA, it starts the timer corresponding to the first TAG (that is, the first timing advance timer); for example, when the terminal receives the second message, it starts the timer corresponding to the first TAG (that is, the first timing advance timer). Among them, during the operation of the first timing advance timer, it can be considered that the terminal and the first TAG of the target cell are uplink synchronized. In the case where the first TA is not obtained, there is no need to start the timer corresponding to the first TAG.

[0332] 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). Among them, during the operation of the second timing advance timer, it can be considered that the second TAG of the terminal and the target cell are uplink synchronized. In the case where the second TA is not obtained, there is no need to start the timer corresponding to the second TAG.

[0333] Among them, the duration of the first timing advance timer and / or the duration of the second timing advance timer are provided by the second network device to the terminal.

[0334] Optionally, the above method further includes:

[0335] S905, the second network device sends downlink control information to the terminal, and the downlink control information is used to indicate uplink resources or downlink resources; correspondingly, the terminal receives the downlink control information, and in the case where the downlink control information or the resource indicated by the downlink control information corresponds to the first TAG, the terminal can determine that the handover is completed.

[0336] The above S905 can refer to S507 in Embodiment 1.

[0337] By adopting 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 according to the first TA measurement, the terminal can determine that the first TA information corresponds to the first TAG, which is convenient for the terminal to quickly perform effective data transmission on the target cell and improve the data transmission efficiency.

[0338] Embodiment 6

[0339] In Embodiment 6, based on Embodiment 5, taking Scenario 2 as an example, a possible implementation process will be described.

[0340] Figure 10 It is a schematic flow diagram corresponding to the communication method provided in Embodiment 6 of this application. As Figure 10 shown, the method includes:

[0341] S1001, the CU sends Message 1 to the second DU, and Message 1 is used to request LTM configuration.

[0342] Exemplarily, Message 1 may include a request message, and the request message is used to request TA measurement configuration for multiple TAGs.

[0343] S1002, the second DU sends Message 2 to the CU, and Message 2 includes the LTM configuration information of the first cell; correspondingly, the CU receives Message 2.

[0344] Here, the LTM configuration information of the first cell includes the lower-layer RRC configuration, reference signal configuration, transmission configuration indication status configuration, and random access channel configuration of the first cell. Message 2 also includes the fourth corresponding relationship information (and the fifth corresponding relationship information).

[0345] For example, when Message 1 includes request information, Message 2 includes the fourth corresponding relationship information (and the fifth corresponding relationship information). Alternatively, Message 1 may not include request information. In this case, the second DU actively sends the fourth corresponding relationship information (and the fifth corresponding relationship information).

[0346] S1003, the CU sends Message 3 to the first DU; correspondingly, the first DU receives Message 3.

[0347] 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.

[0348] S1004, the first DU sends Message 4 to the CU; correspondingly, the CU receives Message 4.

[0349] Exemplarily, Message 4 may include the channel state information (CSI) resource configuration of the source cell, and this CSI resource configuration is used for the terminal to send the 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.

[0350] Among them, the message names of Message 1 to Message 4 can refer to the description in Embodiment 2.

[0351] S1005, the CU sends an RRC reconfiguration message to the terminal; correspondingly, the terminal receives the RRC reconfiguration message.

[0352] Here, the RRC reconfiguration message includes the fourth corresponding relationship information (and the fifth corresponding relationship information).

[0353] S1006, the terminal sends an RRC reconfiguration complete message to the CU; correspondingly, the CU receives the RRC reconfiguration complete message.

[0354] S1007, the terminal obtains the first TA according to the first TA measurement.

[0355] S1008, the terminal determines that the first TA corresponds to the first TAG according to the fourth corresponding relationship information in the RRC reconfiguration message.

[0356] Optionally, the terminal obtains the second TA according to the second TA measurement; and determines that the second TA corresponds to the second TAG according to the fifth corresponding relationship information in the RRC reconfiguration message.

[0357] S1009, The terminal sends a measurement report to the first DU, and the measurement report includes the lower-layer measurement results of multiple candidate cells.

[0358] S1010, The first DU sends a handover command message to the terminal, and the handover command message is used to instruct the terminal to hand over to the first cell.

[0359] Among them, the handover command message includes the identification information of the target cell of the handover, and the target cell is the first cell.

[0360] S1011, The terminal accesses the target cell using the TA indicated by the first TA according to the handover command message.

[0361] S1012, The first DU sends an LTM cell change notification message to the CU, and the LTM cell change notification message is used to indicate that a cell handover command has been initiated for the terminal; correspondingly, the CU receives the LTM cell change notification message.

[0362] Here, the LTM cell change notification message includes the identification information of the target cell.

[0363] 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.

[0364] S1014, The second DU determines that the terminal has obtained the TA corresponding to the first TAG according to the measurement of the first TA.

[0365] S1015, The second DU sends downlink control information to the terminal, and the downlink control information is used to indicate uplink resources or downlink resources; correspondingly, 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 handover is completed.

[0366] It can be understood that Figure 10 the process shown Figure 9 corresponds to the process shown, and the steps of the two can be referred 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.

[0367] Regarding the above-mentioned multiple embodiments, it can be understood that:

[0368] (1) In various embodiments of the present application, "corresponding" can also be replaced by "associated", "related", or "mapped". Taking "the first TAG corresponds to the first information" as an example, the first TAG corresponding to the first information means that when there are multiple TAGs, the first TAG among these multiple TAGs can be indexed through the first information.

[0369] (2) In various embodiments of the present application, if there is no special explanation and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be mutually referred to. The technical features in different embodiments can be combined to form new embodiments according to their internal logical relationships. In addition, within the same embodiment, different implementation manners or different examples can also be mutually referred to or referenced.

[0370] (3) The various digital numbers involved in the present application are only for the convenience of description and do not limit the scope of the present application. The step numbers in the above-mentioned flowcharts are only an example of the execution process and do not constitute a limitation on the sequence of step execution, that is, the magnitudes of the step numbers do not mean the sequence of execution. The execution sequence of each step should be determined according to its function and internal logic. In addition, not all the steps shown in each flowchart are steps that must be executed, and some steps can be added or deleted based on the actual needs on the basis of each flowchart.

[0371] The above mainly introduces the solutions provided by the embodiments of the present application from the perspective of the interaction between the network device and the terminal. It can be understood that in order to implement the above functions, the network device and the terminal may include the corresponding hardware structures and / or software modules for executing each function. Those skilled in the art should easily realize that the embodiments of the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in the form of hardware or computer software driving the hardware depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0372] The embodiments of the present application can divide the network device and the terminal into functional units according to the above method examples. For example, each functional unit can be divided corresponding to each function, or two or more functions can be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0373] 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 Figure 11As shown, 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 operations 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, also referred to as a transceiver unit, may include a receiving unit and / or a transmitting unit, which are respectively used to perform receiving and transmitting operations. The device 1100 may further include a storage unit 1101, which is used to store the program code and / or data of the device 1100.

[0374] (1) The device 1100 may be the first network device in the above embodiments. The processing unit 1102 may support the device 1100 to perform the actions of the first network device in the method examples above. Alternatively, the processing unit 1102 mainly performs the internal actions of the first network device in the method examples, and the communication unit 1103 may support the communication between the device 1100 and other devices.

[0375] For example, in one embodiment, the communication unit 1103 is used to: receive a first message, where the first message includes the first timing advance (TA) information of a first cell; determine that the first TA information corresponds to a first timing advance group (TAG) among a plurality of TAGs, where the plurality of TAGs correspond to the first cell; and send a second message to the terminal, where the second message includes the identification information of the target cell for the handover of the terminal, the first TA information, and the identification information of the first TAG corresponding to the first TA information, and the target cell is the first cell.

[0376] In a possible design, the first message further includes a first piece of information corresponding to the first TA information; the communication unit 1103 is further used to: receive a third message, where the third message is used to indicate that the first TAG corresponds to the first piece of information; and the processing unit 1102 is used to: determine that the first TA information corresponds to the first TAG according to the first message and the third message.

[0377] In a possible design, the processing unit 1102 is specifically used to: determine that the first TA information corresponds to the first TAG according to the correspondence between the first TA information and the first piece of information, and the correspondence between the first TAG and the first piece of information.

[0378] In a possible design, the first piece of information indicates at least one of the following: a first transmission and reception point (TRP); a first synchronization signal block (SSB); a first random access resource; where the first TRP corresponds to the first cell.

[0379] In a possible design, the communication unit 1103 is further used to: send a first indication information, where the first indication information is used to indicate that the terminal has obtained the TA corresponding to the first TAG.

[0380] In a possible design, the first message further includes second TA information of the first cell; the processing unit 1102 is specifically configured to: determine that the second TA information corresponds to a second TAG among the multiple TAGs; the second message further includes the second TA information and identification information of the second TAG corresponding to the second TA information.

[0381] In a possible design, the communication unit 1103 is further configured to: send second indication information for indicating that the terminal has obtained the TA corresponding to the second TAG.

[0382] (2) The device 1100 may be the terminal in the above embodiments. The processing unit 1102 may support the device 1100 to perform the actions of the terminal in the above method examples. Alternatively, the processing unit 1102 mainly performs the internal actions of the terminal in the method examples, and the communication unit 1103 may support the communication between the device 1100 and other devices.

[0383] For example, in one embodiment, the communication unit 1103 is configured to: receive a second message, 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, the first TAG being one of the multiple TAGs corresponding to the target cell; the processing unit 1102 is configured to: according to the second message, determine that the first TA information corresponds to the first TAG, and access the target cell using the TA indicated by the first TA information.

[0384] In a possible design, the processing unit 1102 is further configured to: start a timer corresponding to the first TAG when receiving the second message; wherein, during the running of the timer, the terminal is in uplink synchronization with the target cell.

[0385] In a possible design, the communication unit 1103 is further configured to: receive downlink control information on the target cell, the downlink control information being used to indicate a resource, the resource being an uplink resource or a downlink resource; the processing unit 1102 is further configured to: determine that the handover is completed when the downlink control information or the resource indicated by the downlink control corresponds to the first TAG.

[0386] In a possible design, the communication unit 1103 is further configured to: send first indication information for indicating that the terminal has obtained the TA corresponding to the first TAG.

[0387] In a possible design, the second message further includes second TA information and identification information of a second TAG; the processing unit 1102 is further configured to: determine, according to the second message, that the second TA information corresponds to the second TAG.

[0388] In a possible design, the communication unit 1103 is further configured to: send second indication information for indicating that the terminal has obtained the TA corresponding to the second TAG.

[0389] (3) The device 1100 may be the second network device in the foregoing embodiment. The processing unit 1102 may support the device 1100 to perform the actions of the second network device in the foregoing method examples. Alternatively, the processing unit 1102 mainly performs the internal actions of the second network device in the method examples, and the communication unit 1103 may support the communication between the device 1100 and other devices.

[0390] For example, in one embodiment, the communication unit 1103 is configured to: send a third message for indicating that a first TAG among multiple TAGs corresponds to first information, where the multiple TAGs correspond to a first cell; send a first message, where the first message includes first TA information and the first information corresponding to the first TA information; where 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 configured to: determine that the terminal has obtained the TA corresponding to the first TAG.

[0391] In a possible design, the first information indicates at least one of the following: a first TRP; a first SSB; a first random access resource; where the first TRP corresponds to the first cell.

[0392] In a possible design, the communication unit 1103 is further configured to: receive request information for requesting a random access configuration corresponding to the multiple TAGs.

[0393] In a possible design, the communication unit 1103 is further configured to: receive first indication information for indicating that the terminal has obtained the TA corresponding to the first TAG.

[0394] In a possible design, the third message is further used to indicate that a second TAG among the multiple TAGs corresponds to second information, and the first message further includes second TA information and the second information corresponding to the second TA information; where the first message and the third message are further used to determine that the second TA information corresponds to the second TAG; the communication unit 1103 is further configured to: receive second indication information for indicating that the terminal has obtained the TA corresponding to the second TAG.

[0395] It should be understood that the division of units in the above device is only a division of logical functions. In actual implementation, they can be fully or partially integrated into a physical entity, or physically separated. And the units in the device can all be implemented in the form of software called by a processing element; they can also all be implemented in the form of hardware; or some units can be implemented in the form of software called by a processing element, and some units can be implemented in the form of hardware. For example, each unit can be a separately established processing element, or can be integrated in a certain chip of the device. In addition, it can also be stored in the memory in the form of a program and called and executed by a certain processing element of the device to perform the functions of the unit. In addition, all or part of these units can be integrated together or can be independently implemented. The processing element mentioned here can also be called a processor, which can be an integrated circuit with signal processing capabilities. In the implementation process, the operations of the above method or each of the above units can be implemented through the integrated logic circuit of the hardware in the processor element or in the form of software called by the processing element.

[0396] In one example, the units in any of the above devices can be one or more integrated circuits configured to implement the above method. For example: one or more application specific integrated circuits (ASICs), or one or more digital signal processors (DSPs), or one or more field programmable gate arrays (FPGAs), or a combination of at least two of these integrated circuit forms. Again, when the units 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 central processing unit (CPU), or other processors that can call programs. Again, these units can be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0397] The above unit for receiving is an interface circuit of the device, used to receive signals from other devices. For example, when the device is implemented in the form of a chip, the receiving unit is the interface circuit of the chip for receiving signals from other chips or devices. The above unit for sending is an interface circuit of the device, used to send signals to other devices. For example, when the device is implemented in the form of a chip, the sending unit is the interface circuit of the chip for sending signals to other chips or devices.

[0398] See Figure 12 , which is a schematic structural diagram of a network device provided by an embodiment of the present application. The network device can be applied to, for exampleFigure 1 In the communication system shown, the functions of the network device in the above method embodiments are performed. As Figure 12 shown, the network device 120 may 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 part is mainly used for the transceiver of radio frequency signals, the conversion between radio frequency signals and baseband signals, and partial baseband processing. The CU 1202 may include at least one processor 12022 and at least one memory 12021.

[0399] The CU 1202 part is mainly used for baseband processing, controlling the network device, etc. The DU 1201 and the CU 1202 may be physically set together or physically separated, that is, a distributed base station. The CU 1202 is the control center of the network device and can also be called a processing unit, mainly used to complete the baseband processing function. For example, the CU 1202 may be used to control the network device to execute the operation process of the network device in the above method embodiments.

[0400] In addition, optionally, the network device 120 may include one or more radio frequency units, one or more DUs, and one or more CUs. Among them, the DU may include at least one processor 12013 and at least one memory 12014, the radio frequency unit may include at least one antenna 12011 and at least one radio frequency unit 12012, and the CU may include at least one processor 12022 and at least one memory 12021.

[0401] In one example, the CU1202 may be composed of one or more single boards. Multiple single boards may jointly support a radio access network with a single access indication (such as a 5G network), or may separately support radio access networks with different access systems (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 provided 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. Multiple single boards may jointly support a radio access network with a single access indication (such as a 5G network), or may separately support radio access networks with different access systems (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 provided 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.

[0402] Figure 12 The network device shown can implement each process related to the network device in the above method embodiments. Figure 12 The operations and / or functions of each module in the network device shown are respectively for implementing the corresponding processes in the above method embodiments. For details, reference may be made to the descriptions in the above method embodiments. To avoid repetition, the detailed descriptions are appropriately omitted here.

[0403] See Figure 13 , which is a schematic structural diagram of a terminal provided in an embodiment of the present application. The terminal can be applied to, for example, Figure 1 the communication system shown, and is used to implement the operations of the terminal in the above embodiments. As Figure 13 shown, 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 the 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. After the radio frequency part 1320 processes the information of the terminal, it is sent to the network device through the antenna 1310.

[0404] The signal processing section 1330 may include a modulation and demodulation subsystem for implementing the processing of each communication protocol layer of data; it may also include a central processing subsystem for implementing the processing of the terminal operating system and the application layer; in addition, it may also include other subsystems, such as a multimedia subsystem, a peripheral subsystem, etc., where the multimedia subsystem is used to implement the control of the terminal camera, screen display, etc., and the peripheral subsystem is used to implement the connection with other devices. The modulation and demodulation subsystem may be a separately provided chip.

[0405] The modulation and demodulation subsystem may include one or more processing elements 1331, for example, including a main control CPU and other integrated circuits. In addition, the modulation and demodulation subsystem may also include a storage element 1332 and an interface circuit 1333. The storage element 1332 is used to store data and programs, but the programs for executing the methods performed by the terminal in the above methods may not be stored in the storage element 1332, but in a memory outside the modulation and demodulation subsystem, and are loaded and used by the modulation and demodulation subsystem when in use. The interface circuit 1333 is used to communicate with other subsystems.

[0406] The modulation and demodulation subsystem may be implemented by a chip, which includes at least one processing element and an interface circuit, where the processing element is used to execute each step of any of the methods performed by the above terminal, and the interface circuit is used to communicate with other devices. In one implementation, the units for implementing each step of the above methods in the terminal may be implemented in the form of a processing element scheduler. For example, a device for a terminal includes a processing element and a storage element, and the processing element calls the program stored in the storage element to execute the methods performed by the terminal in the above method embodiments. The storage element may be a storage element on the same chip as the processing element, that is, an on-chip storage element.

[0407] In another implementation, the programs for executing the methods performed by the terminal in the above methods may be in a storage element on a different chip from the processing element, that is, an off-chip storage element. At this time, the processing element calls or loads the program from the off-chip storage element onto the on-chip storage element to call and execute the methods performed by the terminal in the above method embodiments.

[0408] In yet another implementation, the units for implementing each step of the above methods in the terminal may be configured as one or more processing elements, and these processing elements are provided on the modulation and demodulation subsystem. Here, the processing elements may be integrated circuits, for example: one or more ASICs, or, one or more DSPs, or, one or more FPGAs, or a combination of these types of integrated circuits. These integrated circuits may be integrated together to form a chip.

[0409] The units in the terminal for implementing each step in the above method can be integrated together and implemented in the form of an SOC. This SOC chip is used to implement the above method. At least one processing element and storage element can be integrated in this chip, and the method executed by the above terminal is implemented in the form of a program stored in the storage element being called by the processing element; alternatively, at least one integrated circuit can be integrated in this chip for implementing the method executed by the above terminal; or, the above implementation manners can be combined, and the functions of some units are implemented in the form of a program called by the processing element, while the functions of some units are implemented in the form of an integrated circuit.

[0410] It can be seen that the device for the terminal described above may include at least one processing element and an interface circuit, where at least one processing element is used to execute any method executed by the terminal provided in the above method embodiments. The processing element can execute some or all of the steps executed by the terminal in a first manner: that is, by calling the program stored in the storage element; or in a second manner: that is, by combining the integrated logic circuit in the processor element with instructions to execute some or all of the steps executed by the terminal; of course, it can also combine the first manner and the second manner to execute some or all of the steps executed by the terminal.

[0411] The processing element here is the same as described above and can be implemented by a processor, and the function of the processing element can be the same as that of the Figure 11 processing unit described. Exemplarily, the processing element can be a general-purpose processor, such as a CPU, or can also be 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, etc., 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 Figure 11 storage unit described. The storage element can be a single memory or a collective term for multiple memories.

[0412] Figure 13 The terminal shown can implement each process related to the terminal in the above method embodiments. Figure 13 The operations and / or functions of each module in the terminal shown are respectively for implementing the corresponding processes in the above method embodiments. For details, reference can be made to the description in the above method embodiments. To avoid repetition, the detailed description is appropriately omitted here.

[0413] The terms "system" and "network" in the embodiments of the present application may be used interchangeably. "At least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single items 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. Also, 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.

[0414] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, optical storage, etc.) that contain computer-usable program code.

[0415] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0416] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0417] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions for implementing the steps specified in one process or a plurality of processes and / or blocks Figure 1 one process or a plurality of processes and / or blocks Figure 1 in one block or a plurality of blocks.

Claims

1. A communication method, characterized in that, the method includes: receiving a first message, the first message including first timing advance (TA) information of a first cell; determining that the first TA information corresponds to a first timing advance group (TAG) among a plurality of TAGs, the plurality of TAGs corresponding to the first cell; sending a second message to a terminal, the second message including identification information of a target cell for handover of the terminal, the first TA information, and identification information of the first TAG corresponding to the first TA information, the target cell being the first cell.

2. The method according to claim 1, characterized in that, the first message further includes first information corresponding to the first TA information; the method further 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 a first TAG among a plurality of TAGs includes: determining, according to the first message and the third message, 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: determining, according to the correspondence between the first TA information and the first information, and the correspondence between the first TAG and the first information, 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: a first transmission and reception point (TRP); a first synchronization signal block (SSB); a first random access resource; wherein, 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 includes: sending first indication information, the first indication information being used to indicate that the terminal has obtained the TA corresponding to the first TAG.

6. The method according to any one of claims 1 to 5, characterized in that, the first message further 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 further includes the second TA information and identification information of the second TAG corresponding to the second TA information.

7. The method according to claim 6, characterized in that, the method further includes: sending second indication information, the second indication information being used to indicate that the terminal has obtained the TA corresponding to the second TAG.

8. A communication method, characterized in that, the method includes: receiving a second message, the second message including identification information of a target cell for handover of a terminal, first TA information, and identification information of a first TAG, the first TAG being one of a plurality of TAGs, the plurality of TAGs corresponding to the target cell; determining, according to the second message, that the first TA information corresponds to the first TAG, and accessing the target cell using the TA indicated by the first TA information.

9. The method according to claim 8, Characterized in that, 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 in uplink synchronization with the target cell.

10. The method according to claim 8 or 9, Characterized in that, The method further includes: Receiving downlink control information on the target cell, the downlink control information being used to indicate a resource, the resource being an uplink resource or a downlink resource; Determining that the handover is completed when the downlink control information or the resource indicated by the downlink control corresponds to the first TAG.

11. The method according to any one of claims 8 to 10, Characterized in that, The method further includes: Sending first indication information, the first indication information being used to indicate that the terminal has obtained the TA corresponding to the first TAG.

12. The method according to any one of claims 8 to 11, Characterized in that, The second message further includes second TA information and identification information of a second TAG; The method further 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 includes: Sending second indication information, the second indication information being used to indicate that the terminal has obtained the TA corresponding to the second TAG.

14. A communication method, Characterized in that, The method includes: Sending a third message, the third message being used to indicate that a first TAG among a plurality of TAGs corresponds to first information, the plurality of TAGs corresponding to a first cell; Sending a first message, the first message including 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; Determining that the terminal has obtained 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: A first TRP; a first SSB; a first random access resource; Wherein, the first TRP corresponds to the first cell.

16. The method according to claim 14 or 15, Characterized in that, The method further includes: Receiving request information, the request information being used to request a random access configuration corresponding to the plurality of TAGs.

17. The method according to any one of claims 14 to 16, Characterized in that, Determining that the terminal has obtained the TA corresponding to the first TAG includes: Receiving first indication information, the first indication information being used to indicate that the terminal has obtained the 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 plurality of TAGs corresponds to second information, the first message further includes 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 includes: Receive second indication information, where the second indication information is used to indicate that the terminal has obtained the TA corresponding to the second TAG.

19. A communication device, characterized in that, it includes a module for performing the method according to 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 performs 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 perform the method according to any one of claims 1 to 7 above, the terminal is used to perform the method according to any one of claims 8 to 13 above, and the second network device is used to perform the method according to any one of claims 14 to 18 above.

22. A computer-readable storage medium, characterized in that, a computer program or instruction is stored in the storage medium, and 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 the computer reads and executes the computer program product, the computer is caused to perform 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