Communication methods and communication devices

Abstract

This application provides a communication method and a communication device applicable to the field of L1 / L2 triggered mobility. The method includes: a first network device receiving information regarding the timing advance (TA) of a first candidate cell, wherein the first candidate cell does not belong to the first network device; and the first network device transmitting an identifier of the target cell for switching and first instruction information to a terminal device, wherein the first instruction information instructs the terminal device to access the target cell using a random access channel-skip scheme, wherein the target cell is the first candidate cell. Specifically, assuming that the first network device has obtained information regarding the TA of the first candidate cell, the first network device transmits the first instruction information and an identifier of the target cell for switching (which is the first candidate cell) to the terminal device, so that the terminal device can directly access the target cell without initiating a random access procedure to the first candidate cell. In this way, the amount of random access procedures initiated by the terminal device can be reduced.

Description

Technical Field

[0001] This application relates to communication technologies, and more specifically, to communication methods and communication devices.

Background Art

[0002] In the field of communications, the movement of a terminal device triggers cell switching in a plurality of pre-configured candidate cells. Specifically, the serving cell of the terminal device can be switched to any one of the plurality of candidate cells. The decision for cell switching is made by the distributed unit (DU) of the access network device. Specifically, the terminal device reports a measurement report of the candidate cell to the DU, and the DU determines the candidate cell as the target cell for switching based on the measurement report of the candidate cell, and in the cell switching command, instructs the serving cell of the terminal device to be switched to the target cell.

[0003] After the cell switching is completed, the terminal device performs data communication with the DU corresponding to the target cell. Due to the frequent movement of the terminal device, the DU may quickly trigger a plurality of subsequent cell switchings in a plurality of candidate cells. In this case, the terminal device needs to start a random access procedure for all candidate cells in order to obtain the timing advance (TA) of all candidate cells.

[0004] However, in the above method, the terminal device starts excessive random access procedures, resulting in high power consumption and high random access interference. How to reduce the amount of random access procedures started by the terminal device is an urgent technical problem to be solved.

Summary of the Invention

Problems to be Solved by the Invention

[0005] This application provides a communication method and communication device for reducing the amount of random access procedures initiated by a terminal device. [Means for solving the problem]

[0006] According to the first embodiment, a communication method is provided. This method includes: a terminal device determining information regarding the timing advance TA of a first candidate cell; and the terminal device reporting the information regarding the TA of the first candidate cell to a first network device.

[0007] Specifically, the terminal device reports information about the TA of the first candidate cell to the first network device, and as a result, the first network device can obtain information about the TA of the first candidate cell. In response, the first network device may determine, based on the information about the TA of the first candidate cell, whether it is necessary to trigger the terminal device to initiate a random access procedure to the first candidate cell. When the network device determines that it is not necessary to trigger the terminal device to initiate a random access procedure to the first candidate cell, the amount of random access procedures that the terminal device needs to initiate can be effectively reduced.

[0008] In a possible implementation, the method further includes a terminal device receiving instruction information, which instructs the device to report information regarding the TA of candidate cells, the candidate cells including a first candidate cell.

[0009] In this way, terminal devices can report information about candidate cell TAs based on the instructions in the instruction information. This helps to improve the efficiency of information exchange between terminal devices and network devices.

[0010] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0011] Specifically, the information regarding the TA of the first candidate cell may be the TA value, valid indication information, remaining valid time, a time offset, etc. This information helps the first network device determine whether it needs to trigger a terminal device to initiate a certain amount of random access procedures to the first candidate cell. When the first network device determines, based on one or more items of the above information, that it does not need to trigger a terminal device to initiate random access procedures to the first candidate cell, it can effectively reduce the amount of random access procedures that the terminal device needs to initiate.

[0012] In a possible implementation, the terminal device receiving instruction information includes: the terminal device receiving instruction information and an identifier of a target cell for switching from a second network device, wherein the target cell is a second candidate cell, and the second candidate cell belongs to the first network device; or the terminal device receiving instruction information from the first network device.

[0013] Specifically, a terminal device may receive instruction information in multiple ways. For example, the terminal device may receive instruction information from a second network device, in which case the second network device is the terminal device's serving network device, or the terminal device may receive instruction information from a first network device, in which case the first network device is the terminal device's serving network device.

[0014] In possible implementations, the second candidate cell is different from the first candidate cell.

[0015] In this way, this helps reduce the number of random access procedures that the terminal device needs to initiate.

[0016] In possible implementations, the instruction information would instruct the system to report information about the TA of the first candidate cell.

[0017] In this way, the terminal device can improve the efficiency of information exchange between the terminal device and the network device by reporting information about the TA of the first candidate cell to the network device based on the instructions in the instruction information.

[0018] In possible implementations, the first candidate cell does not belong to the first network device.

[0019] According to a second aspect, a communication method is provided, comprising: a first network device receiving information relating to the timing advance TA of a first candidate cell, wherein the first candidate cell does not belong to the first network device; and the first network device transmitting an identifier of a target cell for switching and first instruction information to a terminal device, wherein the first instruction information instructs to access the target cell using a random access channel-skip scheme, wherein the target cell is the first candidate cell.

[0020] Specifically, assuming that the first network device has obtained information about the TA of the first candidate cell, the first network device sends the first instruction information and the identifier of the target cell for switching (which is the first candidate cell) to the terminal device. As a result, the terminal device can directly access the target cell without initiating a random access procedure for the first candidate cell. In this way, the number of random access procedures initiated by the terminal device can be reduced.

[0021] Specifically, the first network device can determine, based on the acquired information regarding the TA of the first candidate cell, that the terminal device and / or network device corresponding to the first candidate cell possess the TA of the first candidate cell. After the first network device determines that the terminal device is accessing the first candidate cell, it can perform uplink data transmission between the terminal device and the network device corresponding to the first candidate cell, based on the information regarding the TA of the first candidate cell. Therefore, the first network device determines that it does not need to trigger the terminal device to initiate a random access procedure to the first candidate cell. In this way, the amount of random access procedures initiated by the terminal device can be effectively reduced.

[0022] In a possible implementation, the first network device receiving information about the TA of the first candidate cell includes: the first network device receiving information about the TA of the first candidate cell from a terminal device; or the first network device receiving information about the TA of the first candidate cell from a second network device.

[0023] Thus, the first network device can obtain information about the TA of the first candidate cell in multiple ways. For example, the first network device may receive information about the TA of the first candidate cell from a terminal device, or it may receive information about the TA of the first candidate cell from a second network device.

[0024] In a possible implementation, the method further includes: a first network device sending a second instruction to a terminal device, wherein the second instruction instructs the terminal to report information regarding the TA of a candidate cell, or the second instruction instructs the terminal to report information regarding the TA of a first candidate cell.

[0025] In this way, the first network device can receive information about the TA of the first candidate cell from the terminal device.

[0026] In a possible implementation, the method further includes: a first network device sending request information to a second network device, where the request information is used to request information regarding the TA of a first candidate cell.

[0027] Thus, the first network device can receive information regarding the TA of the first candidate cell from the second network device.

[0028] In a possible implementation, the information regarding the TA of the first candidate cell includes at least one of the following, namely: the TA of the first candidate cell; or indication information indicating that the TA of the first candidate cell is valid; or the remaining valid time of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell, where the time offset corresponds to the period of the TA of the first candidate cell.

[0029] Specifically, the information regarding the TA of the first candidate cell may be a TA value, may be valid indication information, may be the remaining valid time, or may be a time offset, etc. This information helps the first network device determine whether it is necessary to trigger the terminal device to start a certain amount of random access procedures for the first candidate cell. When the first network device determines not to trigger the terminal device to start random access procedures for the first candidate cell based on one or more items of the above information, the amount of random access procedures that the terminal device needs to start can be effectively reduced.

[0030] According to a third aspect, a communication method is provided, wherein a first network device transmits first instruction information to a terminal device, wherein the first instruction information instructs the terminal device to obtain information regarding the TA of a first candidate cell; and the first network device transmits an identifier of a target cell for switching and second instruction information to the terminal device, wherein the target cell is a second candidate cell and the second candidate cell belongs to a second network device, wherein the second instruction information instructs the second network device to report information regarding the TA of the first candidate cell and the first candidate cell does not belong to the second network device.

[0031] Specifically, the first network device can instruct a terminal device to acquire information about the TA of the first candidate cell and to report this information to the second network device. In response, the second network device can determine, based on the acquired information about the TA of the first candidate cell, whether to trigger the terminal device to initiate a random access procedure to the first candidate cell. When the second network device determines that it does not need to trigger the terminal device to initiate a random access procedure to the first candidate cell, it can effectively reduce the amount of random access procedures that the terminal device needs to initiate.

[0032] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0033] Specifically, the information regarding the TA of the first candidate cell may be the TA value, valid indication information, remaining valid time, a time offset, etc. This information helps the second network device determine whether it needs to trigger the terminal device to initiate a certain amount of random access procedures to the first candidate cell. When the second network device determines, based on one or more items of the above information, that it does not need to trigger the terminal device to initiate random access procedures to the first candidate cell, it can effectively reduce the amount of random access procedures that the terminal device needs to initiate.

[0034] In possible implementations, the second candidate cell is different from the first candidate cell.

[0035] In this way, this helps reduce the amount of random access procedures that the terminal device needs to initiate.

[0036] According to a fourth aspect, a communication method is provided, comprising: a first network device obtaining information relating to the timing advance TA of a first candidate cell, wherein the first candidate cell belongs to a first network device or a third network device, and the information relating to the TA of the first candidate cell is used to determine whether to use a random access channel-skip scheme; and the first network device transmitting the information relating to the TA of the first candidate cell to a second network device by using a fourth network device.

[0037] Specifically, the first network device can transmit information it possesses regarding the TA of the first candidate cell to the second network device by using the fourth network device. This helps the second network device determine whether it needs to trigger a terminal device to initiate a random access procedure to the first candidate cell based on the information regarding the TA of the first candidate cell. When the second network device determines that it does not need to trigger a terminal device to initiate a random access procedure to the first candidate cell, it can effectively reduce the amount of random access procedures that the terminal device needs to initiate.

[0038] In a possible implementation, the acquisition of information about the TA of a first candidate cell by a first network device includes: the first network device receiving information about the TA of the first candidate cell from a fourth network device; or the first network device receiving a contention-free random access preamble transmitted by a terminal device in the first candidate cell; and the first network device determining information about the TA of the first candidate cell based on the contention-free random access preamble.

[0039] In a possible implementation, the method further includes: a first network device receiving request information from a fourth network device, where the request information is used to request information about the TA of a first candidate cell.

[0040] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0041] According to a fifth aspect, a communication method is provided, comprising: a first network device receiving a contention-free random access preamble for a first candidate cell, the contention-free random access preamble being used to determine information regarding the TA of the first candidate cell; and the first network device transmitting information regarding the TA of the first candidate cell to a third network device using a second network device.

[0042] In a possible implementation, the method further includes: a first network device receiving request information from a second network device, where the request information is used to request the acquisition of information regarding the TA of a first candidate cell.

[0043] In a possible implementation, the information regarding the TA of the first candidate cell is at least one of the following: 1 The TA of the candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; wherein the time offset corresponds to the duration of the TA of the first candidate cell.

[0044] According to a sixth aspect, a communication device is provided, comprising: a processing unit configured to determine information relating to the TA of a first candidate cell; and a transceiver unit configured to report the information relating to the TA of the first candidate cell to a first network device.

[0045] In a possible implementation, the transceiver unit is further configured to receive instruction information, which instructs the unit to report information regarding the TA of candidate cells, including a first candidate cell.

[0046] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0047] In a possible implementation, the transceiver unit is further configured to receive instruction information and an identifier of the target cell to be switched from a second network device, where the target cell is a second candidate cell, and the second candidate cell belongs to the first network device; or the transceiver unit is further configured to receive instruction information from the first network device.

[0048] In possible implementations, the second candidate cell is different from the first candidate cell.

[0049] In possible implementations, the instruction information would instruct the system to report information about the TA of the first candidate cell.

[0050] In possible implementations, the first candidate cell does not belong to a communication device.

[0051] According to a seventh aspect, a communication device is provided, comprising a transceiver unit configured to receive information relating to a TA of a first candidate cell, wherein the first candidate cell does not belong to the communication device. The transceiver unit is further configured to transmit to a terminal device an identifier of a target cell for switching and first instruction information, wherein the first instruction information instructs to access the target cell in a random access channel-skip scheme, and the target cell is the first candidate cell.

[0052] In possible implementations, the transceiver unit may be further configured to receive information about the TA of the first candidate cell from a terminal device; or the transceiver unit may be further configured to receive information about the TA of the first candidate cell from a second network device.

[0053] In possible implementations, the transceiver unit is further configured to transmit a second instruction to a terminal device, where the second instruction instructs the terminal to report information regarding the TA of a candidate cell, or the second instruction instructs the terminal to report information regarding the TA of a first candidate cell.

[0054] In a possible implementation, the transceiver unit is further configured to send request information to a second network device, where the request information is used to request information about the TA of the first candidate cell.

[0055] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0056] According to the eighth aspect, a communication device is provided, comprising a transceiver unit configured to transmit first instruction information to a terminal device, the first instruction information instructing the terminal device to obtain information regarding the TA of a first candidate cell. The transceiver unit is further configured to transmit an identifier of a target cell for switching and second instruction information to the terminal device, where the target cell is a second candidate cell, the second candidate cell belongs to a second network device, and the second instruction information instructs the second network device to report information regarding the TA of the first candidate cell, the first candidate cell does not belong to the second network device.

[0057] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0058] In possible implementations, the second candidate cell is different from the first candidate cell.

[0059] According to the ninth aspect, a communication device is provided, comprising: a processing unit configured to acquire information relating to the timing advance TA of a first candidate cell, wherein the first candidate cell belongs to a first network device or a third network device, and the information relating to the TA of the first candidate cell is used to determine whether to use a random access channel-skip scheme; and a transceiver unit configured to transmit the information relating to the TA of the first candidate cell to a second network device by using a fourth network device.

[0060] In possible implementations, the transceiver unit is further configured to receive information about the TA of the first candidate cell from a fourth network device, or the transceiver unit is configured to receive a contention-free random access preamble transmitted by a terminal device in the first candidate cell, and the processing unit is further configured to determine information about the TA of the first candidate cell based on the contention-free random access preamble.

[0061] In possible implementations, Transmitter / Receiver Unit The first network device is further configured to receive request information from the fourth network device, where the request information is used to request information about the TA of the first candidate cell.

[0062] In a possible implementation, information regarding the TA of the first candidate cell includes at least one of the following: the TA of the first candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; where the time offset corresponds to the duration of the TA of the first candidate cell.

[0063] According to a tenth aspect, a communication device is provided, comprising a transceiver unit configured to receive a contention-free random access preamble of a first candidate cell, the contention-free random access preamble being used to determine information about the TA of the first candidate cell. The transceiver unit is configured to transmit the information about the TA of the first candidate cell to a third network device by using a second network device.

[0064] In a possible implementation, the transceiver unit is further configured to receive request information from a second network device, which is used to request the acquisition of information about the TA of the first candidate cell.

[0065] In a possible implementation, the information regarding the TA of the first candidate cell is at least one of the following: 1 The TA of the candidate cell; or indicator information indicating that the TA of the first candidate cell is valid; or the remaining validity period of the TA of the first candidate cell; or the time offset of the TA of the first candidate cell; wherein the time offset corresponds to the duration of the TA of the first candidate cell.

[0066] According to the eleventh aspect, a communication device including a processor is provided. The processor is configured to enable the communication device to perform a method according to any one of the first aspect and possible implementations of the first aspect by executing a computer program or instructions, or by using logic circuits, the communication device to perform a method according to any one of the second aspect and possible implementations of the second aspect, the communication device to perform a method according to any one of the third aspect and possible implementations of the third aspect, the communication device to perform a method according to any one of the fourth aspect and possible implementations of the fourth aspect, or the communication device to perform a method according to any one of the fifth aspect and possible implementations of the fifth aspect.

[0067] In possible implementations, the communication device further includes memory configured to store computer programs or instructions.

[0068] In possible implementations, the communication device further includes a communication interface configured to input and / or output signals.

[0069] According to a twelfth aspect, a communication device is provided that includes a logic circuit and an input / output interface. The input / output interface is configured to input and / or output signals. The logic circuit is configured to perform a method according to any one of the first aspect and possible implementations thereof. Alternatively, the logic circuit is configured to perform a method according to any one of the second aspect and possible implementations thereof. Alternatively, the logic circuit is configured to perform a method according to any one of the third aspect and possible implementations thereof. Alternatively, the logic circuit is configured to perform a method according to any one of the fourth aspect and possible implementations thereof. Alternatively, the logic circuit is configured to perform a method according to any one of the fifth aspect and possible implementations thereof.

[0070] According to the thirteenth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program or instruction. When the computer program or instruction is executed on a computer, a method according to any one of the first aspect and possible implementations of the first aspect is executed, or a method according to any one of the second aspect and possible implementations of the second aspect is executed, or a method according to any one of the third aspect and possible implementations of the third aspect is executed, or a method according to any one of the fourth aspect and possible implementations of the fourth aspect is executed, or a method according to any one of the fifth aspect and possible implementations of the fifth aspect is executed.

[0071] According to the 14th aspect, a computer program product including instructions is provided. When the instructions are executed on a computer, one of the methods according to the first aspect and any possible implementation of the first aspect is executed, or one of the methods according to the second aspect and any possible implementation of the second aspect is executed, or one of the methods according to the third aspect and any possible implementation of the third aspect is executed, or one of the methods according to the fourth aspect and any possible implementation of the fourth aspect is executed, or one of the methods according to the fifth aspect and any possible implementation of the fifth aspect is executed.

[0072] According to the 15th aspect, a chip including a logic circuit is provided. The logic circuit is configured to perform a method according to any one of the first aspect and possible implementations of the first aspect. Alternatively, the logic circuit is configured to perform a method according to any one of the second aspect and possible implementations of the second aspect. Alternatively, the logic circuit is configured to perform a method according to any one of the third aspect and possible implementations of the third aspect. Alternatively, the logic circuit is configured to perform a method according to any one of the fourth aspect and possible implementations of the fourth aspect. Alternatively, the logic circuit is configured to perform a method according to any one of the fifth aspect and possible implementations of the fifth aspect.

[0073] For a description of the advantageous effects of the fourth through fifteenth embodiments, please refer to the description of the advantageous effects of the first through third embodiments. Further details will not be explained here. [Brief explanation of the drawing]

[0074] [Figure 1] This is a diagram of a communication system 100 to which an embodiment of this application can be applied.

[0075] [Figure 2] This is a diagram of application scenario 200 according to the embodiment of this application.

[0076] [Figure 3]This is a diagram illustrating the cell switching procedure.

[0077] [Figure 4] This is a schematic dialogue flowchart of the communication method 400 according to the embodiment of this application.

[0078] [Figure 5] This is a schematic dialogue flowchart of the communication method 500 according to the embodiment of this application.

[0079] [Figure 6A] This is a schematic dialogue flowchart of the communication method 600 according to the embodiment of this application. [Figure 6B] This is a schematic dialogue flowchart of the communication method 600 according to the embodiment of this application.

[0080] [Figure 7A] This is a schematic dialogue flowchart of the communication method 700 according to the embodiment of this application. [Figure 7B] This is a schematic dialogue flowchart of the communication method 700 according to the embodiment of this application.

[0081] [Figure 8A] This is a schematic dialogue flowchart of the communication method 800 according to the embodiment of this application. [Figure 8B] This is a schematic dialogue flowchart of the communication method 800 according to the embodiment of this application.

[0082] [Figure 9] This is a diagram showing the structure of a communication device 900 according to an embodiment of this application.

[0083] [Figure 10] This is a diagram showing the structure of a communication device 1000 according to an embodiment of this application.

[0084] [Figure 11] This is a diagram showing the structure of a communication device 1100 according to an embodiment of this application.

[0085] [Figure 12] This is a diagram showing the structure of a communication device 1200 according to an embodiment of this application.

[0086] [Figure 13] This is a diagram showing the structure of a communication device 1300 according to an embodiment of this application. [Modes for carrying out the invention]

[0087] The technical solution of this application will be described below with reference to the attached drawings.

[0088] The technical solutions in the embodiments of this application may be applied to various communication systems, such as long-term evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, universal mobile telecommunications systems (UMTS), 5th generation (5G) or new radio (NR) systems, 5th generation (6G) and later evolutionary systems, and non-terrestrial network (NTN) systems such as inter-satellite communication systems and satellite communication systems. A satellite communication system includes a satellite base station and terminal devices. The satellite base station provides communication services to the terminal devices. The satellite base station may also communicate with a ground base station. A satellite may function as a base station or as a terminal device. A satellite may be a non-terrestrial base station or non-terrestrial device, such as an unmanned aerial vehicle, a hot air balloon, a low-Earth orbit satellite, a medium-Earth orbit satellite, or a high-Earth orbit satellite.

[0089] The technical solutions in the embodiments of this application are applicable to both homogeneous and heterogeneous network scenarios. In addition, the transmission points are not limited. Cooperative multipoint transmission may be performed between macro base stations, between micro base stations, and between macro base stations and micro base stations. This technical solution is applicable to FDD / TDD systems. The technical solutions in the embodiments of this application are applicable not only to low-frequency scenarios (sub-6G) but also to high-frequency scenarios (above 6GHz), terahertz, optical communications, etc. The technical solutions in the embodiments of this application are applicable not only to communication between network devices and terminals but also to communication between network devices, communication between terminals, communication in the Internet of Vehicles, communication in the Internet of Things, communication in the Industrial Internet, etc.

[0090] The technical solution in the embodiments of this application may also be applied to scenarios in which a terminal is connected to a single base station. The base station connected to the terminal and the core network (CN) connected to the base station are of the same standard. For example, if the CN is a 5G core, the base station is correspondingly a 5G base station, and the 5G base station is directly connected to the 5G core. Alternatively, if the CN is a 6G core, the base station is a 6G base station, and the 6G base station is directly connected to the 6G core. The technical solution in the embodiments of this application is also applicable to dual connectivity (DC) scenarios in which a terminal is connected to at least two base stations.

[0091] The technical solutions in embodiments of this application may also use macro-micro scenarios involving different forms of base stations within a communication network. For example, the base stations may be satellites, balloon stations, or unmanned aerial vehicle stations. The technical solutions in embodiments of this application are also applicable to scenarios in which both wide-coverage and narrow-coverage base stations exist.

[0092] The technical solutions in the embodiments of this application may be applied to scenarios where high reliability service requirements exist, such as ports, industrial production, transportation, and coal mines.

[0093] It can be further understood that the technical solutions in the embodiments of this application may be further applied to 5.5G wireless communication systems, 6G wireless communication systems, and 5.5G and 6G and beyond wireless communication systems. Application scenarios include, but are not limited to, terrestrial cellular communication scenarios, NTN scenarios, satellite communication scenarios, high altitude platform station (HAPS) communication scenarios, vehicle-to-everything (V2X) scenarios, integrated access and backhaul (IAB) scenarios, and reconfigurable intelligent surface (RIS) communication scenarios.

[0094] The terminal in the embodiments of this application may be a device having wireless transceiver functionality, and specifically may be user equipment (UE), access terminal, subscriber unit, subscriber station, mobile station, remote station, remote terminal, mobile device, user terminal, wireless communication device, user agent, or user equipment. The terminal device may alternatively be a satellite phone, mobile phone, smartphone, wireless data card, wireless modem, machine-type communication device, or cordless phone, session initiation protocol (SIP) phone, wireless local loop (WLL) station, personal digital assistant (PDA), customer-premises equipment (CPE), smart point of sale (POS) machine, handheld device with wireless communication capabilities, computing device or other processing device connected to a wireless modem, in-vehicle device, communication device mounted on a high-altitude aircraft, wearable device, unmanned aerial vehicle, robot, terminal device in device-to-device (D2D) communication, terminal device in V2X, virtual reality (VR) terminal device, augmented reality (AR) terminal device, wireless terminal in industrial control, wireless terminal in self-driving, telemedicine (remote) This may include wireless terminals in medical applications, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, and terminal devices in advanced communication networks such as 5G and beyond. This is not limited to the embodiments of this application.

[0095] In embodiments of this application, the communication device configured to implement the functions of a terminal device may be the terminal device itself, or it may be a device capable of supporting the terminal device in implementing its functions, such as a chip system. The device may be mounted on the terminal device or used in combination with the terminal device. In embodiments of this application, the chip system may include a chip, or it may include a chip and other separate components.

[0096] The network device in the embodiments of this application is a device having wireless transceiver functionality and is configured to communicate with a terminal device. The access network device may be a node in a radio access network (RAN), and may also be called a base station, or may be called a RAN node. The access network device may be an evolved NodeB (eNB or eNodeB) in LTE, a base station in a 5G network, such as a gNodeB (gNB), a base station in an evolved public land mobile network (PLMN) beyond 5G, a broadband network gateway (BNG), an aggregation switch, a 3rd generation partnership project (3GPP) access device, etc. For example, the RAN may be configured as a RAN defined by the 3GPP protocol, an open radio access network (O-RAN), or a cloud radio access network (C-RAN).

[0097] The network devices in the embodiments of this application may further include various types of base stations, such as macro base stations, micro base stations (sometimes also called small cells), relay stations, transmitting and receiving points (TRPs), transmitting points (TPs), mobile switching centers, devices that perform base station functions in device-to-device (D2D), vehicle-to-everything (V2X), and machine-to-machine (M2M) communications, and network devices in NTN communication systems. This is not particularly limited to the embodiments of this application.

[0098] The network device in the embodiments of this application may alternatively include network elements or modules that implement some functions of a base station, for example, one or more of the following: a central unit (CU), a distributed unit (DU), or a radio unit (RU). Optionally, the CU may be further separated into a control plane (CP) and a user plane (UP). The functions of the CU and DU may be implemented by different network elements, or by both of the base station's baseband units (BBUs). The functions of the RU may be implemented by the base station's radio frequency unit. For example, the base station's radio frequency device may be a remote radio unit (RRU), a pico remote radio unit (pRRU), an active antenna unit (AAU), or another unit, module, or device having radio frequency processing capabilities. The communication interface protocol between the BBU and the wireless device may be the Common Public Radio Interface (CPRI) interface protocol, the Enhanced Common Public Radio Interface (eCPRI) interface protocol, or the Fronthaul Interface Protocol between the DU and RU in an O-RAN system, etc., but is not limited to these.

[0099] In embodiments of this application, the device implementing the functions of a network device may be a network device, or it may be a device that supports the network device in implementing its functions, such as a chip system. The device may be mounted on a network device or used in combination with a network device. In embodiments of this application, the chip system may include a chip, or it may include a chip and other separate components.

[0100] Figure 1 is a diagram of a communication system 100 to which embodiments of this application are applicable. As shown in Figure 1, the communication system 100 comprises a network device 110 and terminal devices 120. The number of terminal devices 120 and network devices 110 in the communication system 100 is not limited in this application. Figure 1 is merely an example for illustrative purposes and should not be used to limit the scope of protection claimed in this application.

[0101] It can be understood that terminal device 120 may be any of the terminal devices listed above, and network device 110 may be any one of the network devices listed above. This is not limited to this.

[0102] Specifically, the network device 110 may or may not use a central unit (CU)-DU architecture. This is not limited to this. For ease of explanation, this application will be described using an example in which the network device 110 uses a CU-DU architecture. The network device 110 includes one CU and at least one DU, the at least one DU communicating with each other by using the CU.

[0103] In the communication system 100, the DU of the network device 110 can perform cell switching decisions. See Figure 3 for details.

[0104] Figure 2 is a diagram of application scenario 200 according to an embodiment of the present application. As shown in Figure 2, application scenario 200 includes cells #1 to #3. Terminal device 120 is located in cell #1, which is the serving cell of terminal device 120. The terminal device receives an RRC reconfiguration message from cell #1, which includes the candidate cell configuration of the LTM for cells #2 and #3. Cells #2 and #3 are candidate cells, and these candidate cells are potential target cells for switching. Based on the same RRC reconfiguration message, the terminal device performs the following first and second switching.

[0105] Simply put, before the first switchover, cell #1 is the serving cell (i.e., the source serving cell), and cell #2 and cell #1 are the source serving cell. # Cell #3 is a candidate cell. After the first L1 / L2 triggered mobility (LTM) switchover, the serving cell for terminal device 120 switches from cell #1 to cell #2. Cell #2 becomes the serving cell for terminal device 120 after the first switchover and remains the serving cell before the second switchover. Cell #1 becomes a candidate cell for the second switchover, and cell #3 remains a candidate cell. After the second LTM switchover, terminal device 120 switches from cell #2 to cell #3. Cell #3 becomes the serving cell for terminal device 120 after the second LTM switchover. Cell #2 becomes a candidate cell for the third LTM switchover switch, and cell #1 remains a candidate cell. In other words, each of cells #1 through #3 can become a serving cell after the switchover is complete. For ease of distinction and explanation, in this specification, cell #1 is defined as the source serving cell (further explanation provided below), cell #2 is defined as the candidate cell that will function as the target cell for the first switchover (terminal device 120 will be switched from cell #1 to cell #2), and cell #3 is the candidate cell that will not function as the target cell for the first switchover.

[0106] In application scenario 200, the network device 110 may be a base station. If the network device 110 uses a CU-DU partitioned architecture, the network device 110 includes one CU and at least one DU. Cells #1 to #3 may belong to different DUs under the same CU, and all DUs may belong to the network device 110. In this way, application scenario 200 is a base station. Inside This can be applied to the dialogue. In application scenario 200, cells #1 to #3 may belong to different DUs under different CUs. For example, cell #1 belongs to DU1 under CU1, and cell # Cells 2 and 3 belong to DU2 under CU2, where CU1 and CU2 are different. In this way, application scenario 200 can be applied to communication between base stations.

[0107] In conclusion, application scenario 200 can be applied to communication between base stations and communication within base stations. For ease of explanation, in the embodiments of this application, one cell corresponds to one device (hereinafter referred to as "network device"), and the device is defined as a DU. For ease of distinction, in the embodiments of this application, network devices 100 to 400 are defined. Network device 100 (corresponding to cell #1), network device 300 (corresponding to cell #2), and network device 400 (corresponding to cell #3) may all be DUs, while network device 200 is a CU. This will be further explained below.

[0108] It should be noted that the technical solutions disclosed in this application may be applied to communication between base stations (e.g., between gNBs) or to communication within a base station (e.g., within a gNB). For the sake of clarity, communication within a base station will be used primarily as an example for the explanation in this application. However, the relevant explanation may also be applied to a scenario of communication between base stations. For example, network device 100 and network device 200 belong to base station 1, and network device 300 belong to base station 2. This specification provides a unified explanation. Details will not be explained again below.

[0109] Figure 3 is a diagram of the cell switching procedure. The procedure shown in Figure 3 may be applied to a scenario in which DU1 and DU2 belong to the same CU. In addition, the procedure shown in Figure 3 may be applied to a scenario in which DU1 and DU2 belong to different CUs, and the procedures for the two scenarios are similar. For the sake of clarity, this embodiment of the present application uses an example in which the cell switching procedure is applied to a scenario in which DU1 and DU2 belong to the same CU. As shown in Figure 3, the cell switching procedure includes the following steps.

[0110] S310: Terminal device 120 sends measurement report information to DU1.

[0111] In response, DU1 receives measurement report information. This measurement report information includes measurement results for multiple adjacent cells.

[0112] Optionally, the measurement report information is L3 measurement results. The L3 measurement results include the measurement results of multiple adjacent cells that the terminal device 120 performs L3 smoothing on.

[0113] S320:DU1 sends an uplink radio resource control message transfer (UL RRC MESSAGE TRANSFER) message to the CU.

[0114] In response, the CU receives a UL RRC message forwarding message. The UL RRC message forwarding message includes measurement report information in S310.

[0115] S330:CU decides to initiate the LTM configuration procedure.

[0116] Specifically, CU uses measurement report information to determine S 330In this process, it is determined that the LTM configuration procedure needs to be initiated for some or all of the multiple adjacent cells. In other words, the CU determines the LTM candidate cells (which may include cells #1 to #3 in Figure 2) based on the measurement report information, and as a result, the terminal device 120 performs an LTM switchover in the LTM candidate cells.

[0117] S340:CU sends a UE CONTEXT SETUP REQUEST MESSAGE to DU2.

[0118] Specifically, the UE context setup request message includes the identifier of at least one candidate cell. At least one candidate cell includes candidate cell 1 as described below. For example, at least one candidate cell includes cells #1 to #3 in Figure 2. Candidate cell 1 may be cell #2 or cell #3.

[0119] Optionally, at least one candidate cell belongs to multiple adjacent cells. The UE context setup request message is used to request DU2 to provide LTM configuration information for at least one candidate cell, so that terminal device 120 can perform LTM switching based on the LTM configuration information.

[0120] S350:DU2 sends a UE CONTEXT SETUP RESPONSE MESSAGE to the CU.

[0121] Specifically, if DU2 accepts the LTM configuration request, DU2 decides to respond to a UE context setup request message. The UE context setup response message includes lower layer configuration information for at least one candidate cell (e.g., radio link control (RLC) configuration information, media access control (MAC) configuration information, and physical layer (PHY) configuration information). This information can be used by the terminal device 120 to perform LTM switching and data transmission after the LTM switching is complete.

[0122] S360:CU sends a downlink (DL) RRC message transfer message to DU1.

[0123] In response, DU1 receives a DL RRC message forwarding message. The DL RRC message includes an RRC Reconfiguration message, which contains lower-layer configuration information for at least one candidate cell.

[0124] S370:DU1 sends an RRCReconfiguration message to terminal device 120.

[0125] In response to this, terminal device 120 receives an RRCReconfiguration message.

[0126] It can be understood that the cell receiving the RRCReconfiguration message is the source serving cell, i.e., cell #1.

[0127] Specifically, the RRCReconfiguration message includes LTM configuration information provided by DU2 for at least one candidate cell. In other words, terminal device 120 can perform an LTM switchover based on the RRCReconfiguration message.

[0128] Optionally, the RRCReconfiguration message may further include random access common configuration information for each of at least one candidate cell. The random access common configuration information is used by the terminal device 120 to send a contention-free random access preamble in the corresponding candidate cell, and the contention-free random access preamble is used to determine the TA of the candidate cell.

[0129] Note that the RRCReconfiguration message may be used for the initial LTM switchover (first LTM switchover) and may also be used for multiple subsequent switchovers (e.g., second LTM switchover), and no additional RRCReconfiguration messages are required. A unified explanation is provided here. Further details will not be explained again below. S380: Terminal device 120 sends an RRCReconfigurationComplete message to DU1.

[0130] In response, DU1 receives the RRCReconfigurationComplete message.

[0131] S390:DU1 sends the RRCReconfigurationComplete message to the CU.

[0132] In response, the CU receives the RRCReconfigurationComplete message.

[0133] S3100: Terminal device 120 transmits the measurement result of candidate cell 1 to DU1.

[0134] In response, DU1 receives the measurement result for candidate cell 1.

[0135] Before or after S3100, DU1 may send multiple physical downlink control channel (PDCCH) orders to terminal device 120. Multiple PDCCH orders are used to instruct or trigger terminal device 120 to send contention-free random access preambles for all of the candidate cells in order to obtain the TA for the candidate cells. The PDCCH orders include contention-free random access configuration information for the candidate cells, which is used to send the contention-free random access preambles. Terminal device 120 sends contention-free random access preambles for all of at least one candidate cell. random Send the access preamble and retrieve the TA of the candidate cell.

[0136] It can be understood that one PDCCH order corresponds to contention-free random access to one candidate cell. DU1 sends multiple PDCCH orders to terminal device 120 and triggers terminal device 120 to initiate random access procedures for multiple candidate cells.

[0137] Optionally, terminal device 120 also receives a random access response (RAR) message from DU1 or DU2, where the RAR message includes the TA of the candidate cell.

[0138] S3110:DU1 determines candidate cell 1 as the target cell for the switch.

[0139] Specifically, based on the measurement report for candidate cell 1, DU1 determines that the channel quality of candidate cell 1 is better than that of the serving cell, and further determines that the serving cell for terminal device 120 has been switched to candidate cell 1.

[0140] S3120:DU1 sends an LTM command message to terminal device 120.

[0141] In response, terminal device 120 receives an LTM command. The LTM command message includes the identifier of the target cell. Based on the LTM command, terminal device 120 switches to the target cell. The target cell is candidate cell 1 (for example, cell #2).

[0142] S3130:DU1 sends an LTM notification to the CU.

[0143] Specifically, the CU determines the target cell for the LTM switch based on the LTM notification. The LTM notification includes the identifier of the target cell, for example, the identifier of candidate cell 1.

[0144] Furthermore, the CU may send downlink data to the DU2 corresponding to the target cell.

[0145] S3140:DU2 sends an access success message to CU.

[0146] In response, the CU receives an access success message from DU2, which includes the identifier of the target cell and instructs the CU that terminal device 120 has successfully accessed the target cell.

[0147] Specifically, the terminal device 120 may access the target cell using a random access method, for example, via a random access channel, or it may access the target cell using a random access channel-less or random access channel-skip method, for example, directly via a physical uplink shared channel (PUSCH) or physical uplink control channel (PUCCH) without the need to transmit a random access preamble. The PUSCH or PUCCH must carry instruction information a, which instructs DU2 that the terminal device 120 has successfully accessed candidate cell 1.

[0148] It can be understood that after DU2 determines that terminal device 120 has successfully accessed the target cell, DU2 sends an access success message to CU containing the target cell identifier. Furthermore, based on the target cell identifier carried in the access success message, CU can determine that terminal device 120 has successfully switched to the target cell.

[0149] After the cell switchover is complete, the terminal device 120 communicates data with the DU corresponding to the target cell. For ease of explanation, this application will be described using an example where the target cell is cell #2. Cell #1 corresponds to the source DU, cell #2 corresponds to the target DU, and cell #3 corresponds to another candidate DU. Frequent movement of the terminal device 120 can rapidly trigger multiple subsequent cell switches in multiple candidate cells. For example, the serving cell of the terminal device 120 is switched from cell #2 to cell #3. The target DU does not have information about the TA of cell #3 (information about the TA of cell #3 of the terminal device 120), or the target DU does not know whether the terminal device 120 has information about the TA of cell #3, so the target DU instructs the terminal device 120 to initiate a random access procedure to cell #3 in order to obtain the TA of cell #3. As a result, the terminal device 120 must continue to initiate random access procedures to cell #3, resulting in high power consumption and high random access interference for the terminal device 120.

[0150] In this regard, this application provides a communication method and communication device for reducing the amount of random access procedures initiated by a terminal device.

[0151] The communication method and communication device in the embodiments of this application will be described below with reference to the attached drawings.

[0152] It should be noted that Methods 400 and 500 are described from two dimensions, candidate DUs and terminal devices, respectively. However, Methods 400 and 500 are either related at the technical solution level or described from the perspective of different devices based on the same technical challenge.

[0153] Figure 4 is a schematic dialogue flowchart of the communication method 400 according to an embodiment of the present application. The method 400 may be performed by network device 100, network device 200 and terminal device 120, or by modules and / or components (e.g., chips or integrated circuits) mounted on network device 100, network device 200 and terminal device 120 and having corresponding functions. This is not limited to these. For illustrative purposes, an example in which the method 400 is performed by network device 100, network device 200 and terminal device 120 will be used below.

[0154] Please refer to the description in Figure 2 for details on network devices 100 and 200. Further details will not be explained again. Method 400 includes the following steps.

[0155] S410: Network device 100 receives information about candidate cell 1's TA.

[0156] Specifically, network device 100 receives information about the TA of candidate cell 1 from terminal device 120. Candidate cell 1 does not belong to network device 100, but belongs to network device 300 or network device 400. When network device 100 receives information about the TA of candidate cell 1 from terminal device 120, the information about the TA of candidate cell 1 is the same as the information about the TA of terminal device 120. For example, terminal device 120 can perform data transmission with network device 300 or network device 400 corresponding to candidate cell 1 based on the TA of candidate cell 1.

[0157] Please note that candidate cell 1 could be cell #1 or cell #3.

[0158] In a possible implementation, network device 100 is a candidate DU and acts as the target DU for the first failover (the target DU is the DU corresponding to cell #2), network device 200 is a CU, network device 300 is the source DU for the first failover (the source DU is the DU corresponding to cell #1), and network device 400 is another candidate DU that does not act as the target DU for the first failover (the other candidate DU is the DU corresponding to cell #3). For ease of understanding, the following example uses network device 100 as the target DU, network device 300 as the source DU, network device 200 as the CU, and network device 400 as another candidate DU. This definition is also applicable to method 500 below.

[0159] Regarding the case where network device 100 receives information about candidate cell 1's TA:

[0160] In a first possible implementation, when network device 100 (target DU) receives information about candidate cell 1's TA from terminal device 120, network device 100 (target DU) may send information to terminal device 120 instructing it to report the candidate cell's TA. In response, terminal device 120 decides to report information about candidate cell 1's TA from multiple candidate cells and reports the information about candidate cell 1's TA to network device 100 (target DU). The multiple candidate cells include candidate cell 1.

[0161] Optionally, the network device 100 (target DU) may send information to the terminal device 120 instructing it to report the TA of candidate cell 1. Based on this instruction, the terminal device 120 reports information about the TA of candidate cell 1 to the network device 100 (target DU).

[0162] In a second possible implementation, when the network device 100 (target DU) receives information about the TA of candidate cell 1 from the terminal device 120, the network device 100 (target DU) may send information to the terminal device 120 instructing it to report the TA of candidate cell 1. In response, the terminal device 120 reports the information about the TA of candidate cell 1 to the network device 100 (target DU).

[0163] In a third possible implementation, network device 100 (target DU) receives information about the TA of candidate cell 1 from network device 200 (source DU), where candidate cell 1 belongs to either network device 300 (source DU) or network device 400 (another candidate DU). In one example, when candidate cell 1 belongs to network device 300 (source DU), network device 300 (source DU) transmits information about the TA of candidate cell 1 to network device 200 (CU), which then transmits information about the TA of candidate cell 1 to network device 100 (target DU). In another example, when candidate cell 1 belongs to network device 400 (another candidate DU), network device 400 (another candidate DU) transmits information about the TA of candidate cell 1 to network device 200 (CU), which then transmits information about the TA of candidate cell 1 to network device 100 (target DU).

[0164] In the fourth possible implementation, when candidate cell 1 belongs to network device 400 (another candidate DU), network device 400 (another candidate DU) sends information about candidate cell 1's TA to network device 300 (source DU) using network device 200 (CU). Correspondingly, network device 300 (source DU) sends information about candidate cell 1's TA to network device 100 (target DU) using network device 200 (CU).

[0165] S420: The network device 100 sends the identifier of the target cell 1 for switching and instruction information 1 to the terminal device 120, where instruction information 1 instructs the terminal device 120 to access the target cell 1 using the random access channel skip method, and the target cell 1 is candidate cell 1.

[0166] Specifically, the identifier of target cell 1 and instruction information 1 may be carried in an LTM command message. Specifically, network device 100 (target DU) sends an LTM command message to terminal device 120, where the LTM command message includes the identifier of target cell 1 and instruction information 1. The LTM command message may also be a MAC control element (CE).

[0167] Optionally, the identifier of target cell 1 and instruction information 1 may be conveyed in different messages.

[0168] Optionally, the network device 100 (target DU) may transmit the identifier of target cell 1 and instruction information 1 separately. For example, the network device 100 transmits an LTM command message to the terminal device 120, where the LTM command message includes the identifier of target cell 1. Furthermore, the network device 100 (target DU) transmits instruction information 1 to the terminal device 120.

[0169] In possible implementations, when network device 100 (target DU) sends an LTM command message containing the identifier of the target cell for switching to terminal device 120, the following may be predefined: If the LTM command message excludes instruction information that instructs the terminal device 120 to initiate a contention-free random access procedure to the target cell, by default, terminal device 120 is assumed to access the target cell using a random access channel-skip scheme.

[0170] In a possible implementation, when an LTM command message sent by network device 100 (target DU) to terminal device 120 includes an instruction field (which may be a newly added field) that instructs the terminal device 120 to access the target cell using the random access channel-skip / less (RACH-SKIP / LESS) method, the terminal device 120 performs an action based on the instruction field.

[0171] Optionally, instruction information 1 may further instruct the terminal device 120 to access target cell 1 using a random access channel-less method.

[0172] When network device 100 (target DU) receives information regarding the TA of candidate cell 1, it can be understood that network device 100 (target DU) has determined that terminal device 120 and / or the network device corresponding to candidate cell 1 (network device 300 or network device 400) have the TA of candidate cell 1. Therefore, based on the received information regarding the TA of candidate cell 1, network device 100 (target DU) decides to send instruction information 1 to terminal device 120. In possible implementations, instruction message 1 may be the TA of the target cell (terminal device 120 does not store the TA of the target cell) or a random access channel-skip instruction (terminal device 120 does store the TA of the target cell). Terminal device 120 can determine the TA of the target cell based on the received information regarding the TA of the target cell and does not need to obtain the TA of the target cell by initiating a random access procedure. Therefore, terminal device 120 can access the target cell using the random access channel-skip method.

[0173] Optionally, after receiving information about the TA of candidate cell 1, network device 100 (target DU) determines that terminal device 120 and / or the network device corresponding to candidate cell 1 already possess information about the TA of candidate cell 1. After network device 100 (target DU) sends an LTM command message to terminal device 120, terminal device 120 does not need to be triggered to initiate a contention-free random access procedure to the target cell (i.e., candidate cell 1 functions as the target cell) in order to obtain the TA of candidate cell 1 again.

[0174] Optionally, network device 100 (target DU) may receive further information regarding the TA of candidate cell 2. In response, network device 100 (target DU) does not need to trigger terminal device 120 to initiate a contention-free random access procedure on candidate cell 2 before the switch to reacquire the TA of candidate cell 2 based on the acquired information regarding the TA of candidate cell 2. Thus, the number of random access procedures that need to be initiated by terminal device 120 can be reduced. For details on how network device 100 (target DU) acquires information regarding the TA of candidate cell 2, please refer to the method for acquiring information regarding the TA of candidate cell 1 described above.

[0175] Optionally, the network device 100 (target DU) may simultaneously acquire information about the TA of candidate cell 1 and information about the TA of candidate cell 2.

[0176] In conclusion, based on the acquired information about the candidate cell's TA, the network device 100 (target DU) can determine that it does not need to trigger the terminal device 120 to initiate a random access procedure to acquire the candidate cell's TA for which the network device 100 has acquired TA information. This effectively reduces the amount of random access procedures that need to be initiated by the terminal device 120. Therefore, the power consumption of the terminal device 120 and random access interference can be reduced.

[0177] In a possible implementation, instruction information 1 instructing terminal device 120 to access target cell 1 using a random access channel-skip scheme may include: instruction information 1 instructing terminal device 120 to perform data transmission in target cell 1 using a random access channel-skip scheme. In other words, after receiving the LTM command message, terminal device 120 does not need to initiate a random access procedure to candidate cell 1.

[0178] In possible implementations, the function of instructing instruction information 1 to access target cell 1 in a random access channel-skip manner may be achieved through instruction information 1 or specific information elements within instruction information 1, but is not limited to this.

[0179] In possible implementations, candidate cell 1 may be the source serving cell (e.g., cell #1) before the initial LTM switchover of terminal device 120 (which is the first LTM switchover), or it may be a different candidate cell (e.g., cell #3) from the source serving cell before the initial LTM switchover. For example, after the initial LTM switchover, terminal device 120 switches from cell #1 (which is the source serving cell) to cell #2 (which is the target cell). When network device 100 (target DU) determines that terminal device 120 needs to switch from cell #2 to cell #3 or cell #1 (cell #3 or cell #1 may be candidate cell 1), network device 100 (target DU) has obtained information about the TA of cell #3 or cell #1, so network device 100 (target DU) can send instruction information 1 to terminal device 120.

[0180] In a possible implementation, the network device 100 (target DU) receives information about the TA of candidate cell 1 from the terminal device 120, and method 400 may further include the following steps.

[0181] S410a: Network device 100 (target DU) sends instruction information 2 to terminal device 120, where instruction information 2 instructs (or is used to trigger) the reporting of information regarding the TA of candidate cell, or information regarding the TA of candidate cell 1.

[0182] Specifically, when instruction information 2 instructs (or is used to trigger) the reporting of information regarding the TA of a candidate cell, terminal device 120 may report information regarding the TAs of multiple candidate cells to network device 100 (target DU), where the TAs of multiple candidate cells include candidate cell 1. When instruction information 2 instructs (or is used to trigger) the reporting of information regarding the TA of candidate cell 1, terminal device 120 reports information regarding the TA of candidate cell 1 to network device 100 (target DU).

[0183] Optionally, when instruction information 2 instructs (or is used to trigger) the reporting of information regarding the TA of candidate cell 1, instruction information 2 includes identification information of candidate cell 1. Based on the identification information of candidate cell 1 carried in instruction information 2, terminal device 120 decides to report information regarding the TA of candidate cell 1 to network device 100 (target DU).

[0184] As an optional choice, when instruction information 2 instructs (or is used to trigger) the reporting of information regarding the TA of a candidate cell, instruction information 2 does not need to carry the identifier of the candidate cell, and the terminal device 120 decides to report information regarding the TA of candidate cell 1 from among multiple candidate cells to the network device 100 (target DU). For the process by which the terminal device 120 decides on the information regarding the TA of candidate cell 1, it should be understood that you should refer to the explanation in Figure 3. The details will not be explained again here.

[0185] In a possible implementation, network device 100 (target DU) receives information about candidate cell 1's TA from network device 200 (CU), and method 400 may further include the following steps.

[0186] S410b: Network device 100 sends request information 1 to network device 200 (CU), where request information 1 is used to request information about candidate cell 1 or the TA of the candidate cell.

[0187] In response, network device 200 (CU) receives request information 1 from network device 100 (target DU) and, based on request information 1, sends information about the TA of candidate cell 1 to network device 100 (target DU).

[0188] Specifically, network device 200 (CU) is a network device (e.g., network device 300 (source DU) or network device 4) that has information about the TA of candidate cell 1.00 Interact with (another candidate DU)) to obtain information about candidate cell 1's TA, and transmit the information about candidate cell 1's TA to network device 1. 00 Send to [destination].

[0189] Specifically, when network device 100 (target DU) obtains information about the TA of candidate cell 1 from network device 200 (CU), network device 100 (target DU) uses network device 200 (CU) to send request information 1 to the network device corresponding to candidate cell 1 (for example, network device 300 or network device 4). 00 It is sent to ). Request information 1 is used to request information about the TA of candidate cell 1 and includes the identifier of candidate cell 1.

[0190] More specifically, in S410b, network device 110 (target DU) requests information about candidate cell 1's TA from network device 300 (source DU) or network device 400 (another candidate DU) by using network device 200 (CU).

[0191] Optionally, request information 1 includes identification information for candidate cell 1. Based on the identification information for candidate cell 1 carried in request information 1, network device 200 (CU) selects the network device 300 (source DU) or network device 4 that corresponds to candidate cell 1. 00 It is decided to send request information 1 to (another candidate DU).

[0192] Optionally, if Request Information 1 excludes the identification information of the candidate cell, Network Device 200 (CU) broadcasts Request Information 1 to the network device that receives Request Information 1 (e.g., Network Device 300 or Network Device 4). 00In response to request information 1, the network device 100 (target DU) transmits information about candidate cell TAs already possessed by the network device 200 (CU) to the network device 200 (target DU).

[0193] Optionally, before switching terminal device 120 to candidate cell 1, network device 100 (target DU) may also obtain information about candidate cell 2's TA and further decide not to trigger a random access procedure for candidate cell 2. Candidate cell 2 is a different candidate cell from candidate cell 1 and may belong to network device 300 (source DU) or to network device 400 (another candidate DU). For an explanation of obtaining information about candidate cell 2's TA, please refer to the explanation of obtaining information about candidate cell 1's TA. Further details will not be explained again.

[0194] In a possible implementation, information regarding the TA of candidate cell 1 includes at least one of the following: the TA of candidate cell 1; indicator information indicating that the TA of candidate cell 1 is valid; the remaining validity period of the TA of candidate cell 1; and the time offset of the TA of candidate cell 1; the time offset corresponding to the duration of the TA of candidate cell 1.

[0195] When the information regarding the TA of candidate cell 1 includes the TA of candidate cell 1, it can be understood that the information regarding the TA of candidate cell 1 is the absolute TA value of candidate cell 1. The terminal device 120 may determine the TA for uplink transmission based on the absolute TA value of candidate cell 1.

[0196] Specifically, when the information regarding the TA of candidate cell 1 is the TA of candidate cell 1, network device 100 (target DU) is the terminal device 120 and / or the network device corresponding to candidate cell 1 (network device 300 (source DU) or network device 4 00It is determined that (another candidate DU) has the TA of candidate cell 1. When the information regarding the TA of candidate cell 1 is an instruction that indicates the TA of candidate cell 1 is valid, network device 1 00 This refers to the network device (network device 300 (source DU) or network device 4) corresponding to terminal device 120 and / or candidate cell 1. 00 The network device 100 (target DU) determines that the TA of candidate cell 1, owned by (another candidate DU), is valid. When the information regarding the TA of candidate cell 1 is the remaining validity period of the TA of candidate cell 1, the network device 100 (target DU) determines the remaining validity period of the TA of candidate cell 1. If the LTM switchover is performed within the remaining validity period, the network device 100 (target DU) does not need to instruct terminal device 120 to initiate a random access procedure to candidate cell 1. If the LTM switchover is performed beyond the remaining validity period, the network device 100 (target DU) still needs to instruct terminal device 120 to initiate a random access procedure to candidate cell 1. When the information regarding the TA of candidate cell 1 is the time offset of the TA of candidate cell 1, the network device 100 (target DU) determines the elapsed period or duration of the TA of candidate cell 1 based on the time offset. The network device 100 (target DU) may determine the time that has elapsed since the TA of candidate cell 1 was determined based on the time offset. In response to this, the network device 100 (target DU) determines, based on the time offset, whether the terminal device 120 needs to be instructed to initiate a random access procedure to candidate cell 1.

[0197] Optionally, the TA in candidate cell 1 includes both valid and invalid TAs.

[0198] Optionally, network device 100 (target DU) instructs terminal device 120 to report the valid TA for candidate cell 1. In response, terminal device 120 reports the valid TA for candidate cell 1 to network device 100 (target DU). Optionally, terminal device 120 may simultaneously report the valid and invalid TAs for candidate cell 1 to network device 100 (target DU). When terminal device 120 reports the valid TA for candidate cell 1 to network device 100 (target DU), terminal device 120 may also report the remaining validity time, time offset, etc., of the valid TA to network device 100 (target DU).

[0199] Optionally, when network device 100 (target DU) instructs terminal device 120 to report the TA of candidate cell 1, terminal device 120 reports the valid TA of candidate cell 1 to network device 100 (target DU). Optionally, terminal device 120 may simultaneously report the valid and invalid TAs of candidate cell 1 to network device 100 (target DU). Optionally, when terminal device 120 reports the valid TA of candidate cell 1 to network device 100 (target DU), terminal device 120 may also report the remaining validity time, time offset, etc., of the valid TA to network device 100 (target DU).

[0200] It should be noted that Method 400 mainly involves interaction between a source DU, a terminal device 120, a target DU, another candidate DU, and a CU. Method 400 is mainly described by using the target DU as the entity that acquires information about the candidate cell 1's TA and transmits instruction information 1 to the terminal device 120. The technical solution will be described below using the terminal device 120 as the target, with reference to separate attached drawings.

[0201] It should be noted that in Method 400, the source DU, target DU, other candidate DU, and CU may belong to the same base station. In addition, Method 400 may be further applied to scenarios of dialogue between base stations. For example, the source DU and CU may belong to base station 1, and the target DU and other candidate DU may belong to base station 2. For specific methods, please refer to the explanation above. Details will not be explained again here.

[0202] Figure 5 is a schematic dialogue flowchart of the communication method 500 according to an embodiment of the present application. The method 500 may be performed by network device 100, network device 300 and terminal device 120, or by modules and / or components (e.g., chips or integrated circuits) mounted on network device 100, network device 300 and terminal device 120 and having corresponding functions. This is not limited to the embodiments of the present application. As shown in Figure 5, the method 500 includes the following steps:

[0203] Optionally, in S510a, terminal device 120 receives instruction information 2, which instructs the terminal device 120 to report information regarding the TA of the candidate cell.

[0204] Specifically, terminal device 120 may receive instruction information 2 from network device 100 (target DU), or it may receive instruction information 2 from network device 300 (source DU). Candidate cell includes candidate cell 1. Candidate cell 1 does not belong to network device 100 (target DU), and candidate cell 1 belongs to network device 300 (source DU) or network device 4 00 It belongs to (another candidate DU).

[0205] In one example, after terminal device 120 switches to candidate cell 2 managed by network device 100 (target DU), network device 100 (target DU) sends instruction information 2 to terminal device 120, instructing terminal device 120 to report information about the candidate cell's TA.

[0206] For example, when network device 300 (source DU) determines that terminal device 120 needs to be switched to candidate cell 2, which is managed by network device 100 (target DU), the LTM command sent by network device 300 (source DU) to terminal device 120 includes instruction information 2 and the identifier of the target cell for the switch, where the target cell is candidate cell 2 (this is an initial LTM switch). Based on the LTM command, terminal device 120 determines that it needs to report information about the candidate cell's TA to network device 100 (target DU). For details on how network device 300 (source DU) sends instruction information 2 to terminal device 120, please refer to the explanation above. Further details will not be explained again here.

[0207] According to the technical solution described above, the terminal device 120 reports information about the candidate cell's TA based on the instructions in instruction information 2. This helps to improve the efficiency of information exchange between the terminal device 120 and the network device.

[0208] S510: Terminal device 120 determines information regarding the TA of candidate cell 1.

[0209] Specifically, terminal device 120 transmits a contention-free random access preamble for candidate cell 1. In response, network device 300 (source DU) or network device 400 (another candidate DU) receives the contention-free random access preamble for candidate cell 1 and further determines the TA of candidate cell 1. Furthermore, network device 300 (source DU) or network device 400 (another candidate DU) transmits a RAR message to terminal device 120, where the RAR message includes the TA of candidate cell 1. In this way, terminal device 120 may determine the TA of candidate cell 1 according to the method described above.

[0210] Optionally, terminal devices 120 and / or network devices that have information about the TA of candidate cell 1 may determine information such as the validity information of the TA of candidate cell 1, the remaining validity time, or the time offset.

[0211] S520: Terminal device 120 reports information about candidate cell 1's TA to network device 100 (target DU).

[0212] Specifically, when instruction information 2 instructs the terminal device 120 to report information about the TA of a candidate cell, the terminal device 120 may report information about the TA of multiple candidate cells to the network device 100 (target DU), where the multiple candidate cells include candidate cell 1. For a description of candidate cell 1, see Method. 400 Please refer to [the relevant document]. Further details will not be explained here.

[0213] Specifically, terminal device 120 reports information about the TA of candidate cell 1 to network device 100 (target DU), and as a result, network device 100 (target DU) obtains information about the TA of candidate cell 1. In response, network device 100 (target DU) can determine, based on the information about the TA of candidate cell 1, whether terminal device 120 needs to be triggered to initiate a random access procedure to candidate cell 1. When network device 100 (target DU) determines that terminal device 120 does not need to be triggered to initiate a random access procedure to candidate cell 1, the amount of random access procedures that need to be initiated by the terminal device can be effectively reduced.

[0214] Optionally, network device 100 (target DU) may receive further information regarding the TA of candidate cell 3. Based on the acquired information regarding the TA of candidate cell 3, network device 100 (target DU) does not need to trigger terminal device 120 to initiate a random access procedure to candidate cell 3. This reduces the amount of random access procedures that need to be initiated by terminal device 120.

[0215] In conclusion, the network device 100 (target DU) may determine, based on the acquired information about the candidate cell's TA, that it does not need to trigger the terminal device 120 to initiate a random access procedure for the candidate cell from which it has acquired information about the TA. This effectively reduces the amount of random access procedures that the terminal device 120 needs to initiate. Consequently, the power consumption of the terminal device 120 and random access interference can be reduced.

[0216] Please note that for an explanation of the TA information for candidate cell 1 in Method 500, you should refer to Method 400. Further details will not be explained here.

[0217] It should be noted that Method 500 primarily involves interaction between a source DU, terminal device 120, target DU, and another candidate DU. Method 500 is mainly illustrated using the subject of terminal device 120 determining and reporting information regarding candidate cell 1's TA.

[0218] Note that in Method 500, the source DU, target DU, alternative candidate DU, and CU may belong to the same base station. In addition, Method 500 can be further applied to scenarios involving dialogue between base stations. For example, the source DU and CU may belong to base station 1, while the target DU and alternative candidate DU may belong to base station 2. For specific details, please refer to the explanation above. Further details will not be explained again here.

[0219] It should be further noted that Method 500 may also be the peer-side method of Method 400.

[0220] Methods 400 and 500 are described further below with reference to Figures 6A to 8B.

[0221] It should be noted that the methods shown in Figures 6A to 8B are further explanations of methods 400 and 500. In addition, the methods shown in Figures 6A to 8B may also be understood as supplementary explanations of methods 400 and 500. DU1 is network device 300, DU2 is network device 100, DU3 is network device 400, and CU is network device 200.

[0222] Figures 6A and 6B are schematic dialogue flowcharts of communication method 600 according to embodiments of the present application. Method 600 may be performed by terminal devices 120, DU1, DU2, DU3 and CU, or by modules and / or components (e.g., chips or integrated circuits) mounted on terminal devices 120, DU1, DU2, DU3 and CU and having corresponding functions. This is not limited to embodiments of the present application. For illustrative purposes, an example in which method 600 is performed by terminal devices 120, DU1, DU2, DU3 and CU will be used below. As shown in Figures 6A and 6B, method 600 includes the following steps.

[0223] S610: Terminal device 120 sends measurement report information to DU1.

[0224] S620:DU1 sends a UL RRC message forwarding message to the CU.

[0225] S630:CU decides to initiate the LTM configuration procedure.

[0226] For explanations of S610 to S630, please refer to the previously mentioned explanations for S310 to S330. Further details will not be explained here.

[0227] S640:CU1 sends a UE context setup request message to DU2.

[0228] Optionally, CU1 may also send a UE context setup request message to DU3.

[0229] S650:DU2 sends a UE context setup response message to the CU.

[0230] Optionally, DU3 may also send a UE context setup response message to CU.

[0231] For explanations of S640 and S650, please refer to the previously mentioned explanations for S340 and S350. Further details will not be explained here.

[0232] Optionally, the CU may request the LTM configuration procedure for candidate cells managed by DU2 and DU3 via a single UE context setup request message, or each candidate cell may have a single UE context setup request message.

[0233] S660:CU1 sends a DL RRC message forwarding message to DU1.

[0234] S670:DU1 sends an RRCReconfiguration message to terminal device 120.

[0235] S680: Terminal device 120 sends the RRCReconfigurationComplete message to DU1.

[0236] S690:DU1 sends the RRCReconfigurationComplete message to CU1 via UL RRC information.

[0237] For explanations of S660 to S690, see S 360 From S 390 Please refer to the explanation above. Further details will not be explained again here.

[0238] It should be noted that terminal devices 120 and DU1 maintain the TA of a serving cell group, and that a serving cell group includes at least one serving cell. All serving cells within a serving cell group correspond to the same TA and store the most recent TA value used by terminal device 120 to determine the TA for transmitting uplink transmissions within the serving cell. All serving cells within a serving cell group belong to DU1. The TA of a serving cell group is determined by using the downlink reference signal of the secondary timing advance group (STAG) of one of the serving cells or the primary timing advance group (PTAG) of the primary cell for the current carrier aggregation (CA) as the reference for the TA.

[0239] It should be noted that terminal device 120 does not need to detect the DU, but only needs to detect candidate cells. The DU can detect whether a candidate cell belongs to the DU.

[0240] S6100:DU1 sends command 1 and command 2 to terminal device 120.

[0241] In response, terminal device 120 receives command 1 and command 2 from DU1. Command 1 is used to instruct or trigger terminal device 120 to send contention-free random access preamble 1 in candidate cell 1, and contention-free random access preamble 1 is used to determine the TA of candidate cell 1. Command 2 is used to instruct or trigger terminal device 120 to send contention-free random access preamble 2 in candidate cell 2, and contention-free random access preamble 2 is used to determine the TA of candidate cell 2. Command 1 includes the identifier of candidate cell 1, and command 2 includes the identifier of candidate cell 2.

[0242] It can be understood that DU1 may send either command 1 or command 2 to terminal device 120, in other words, it may trigger terminal device 120 to initiate a random access procedure for either candidate cell 1 or candidate cell 2. Therefore, S6100 is simply used as an example for understanding.

[0243] It can be understood that Command 1 contains Contention-Free Random Access Configuration Information 1, which is used to send Contention-Free Random Access Preamble 1, and Command 2 contains Contention-Free Random Access Configuration Information 2, which is used to send Contention-Free Random Access Preamble 2. Candidate cell 2 belongs to DU2, and candidate cell 1 belongs to DU3.

[0244] S6110a: Terminal device 120 transmits contention-free random access preamble 1 in candidate cell 2.

[0245] In response, DU2 receives a contention-free random access preamble 1 from terminal device 120 and determines the TA of candidate cell 2 based on the contention-free random access preamble 1.

[0246] S6110b: Terminal device 120 transmits contention-free random access preamble 2 in candidate cell 1.

[0247] In response, DU3 receives a contention-free random access preamble 2 from terminal device 120 and determines the TA of candidate cell 1 based on the contention-free random access preamble 2.

[0248] Optionally, in S6120a, DU2 sends RAR message 1 to terminal device 120.

[0249] In response, terminal device 120 receives RAR message 1 from DU2. RAR message 1 includes the TA of candidate cell 2. The TA of candidate cell 2 is an absolute TA value. Terminal device 120 may determine the uplink timing advance for uplink transmission in candidate cell 2 based on the absolute TA value of candidate cell 2.

[0250] Optionally, in S6120b, DU3 sends RAR message 2 to terminal device 120.

[0251] In response, terminal device 120 receives RAR message 2 from DU3. RAR message 2 includes the TA of candidate cell 1. The TA of candidate cell 1 is an absolute TA value. Terminal device 120 may determine the uplink timing advance for uplink transmission in candidate cell 1 based on the absolute TA value of candidate cell 1.

[0252] By using S6110~S6120, terminal device 120 completes the random access procedure for candidate cell 1 and candidate cell 2, and obtains the TA for candidate cell 1 and the TA for candidate cell 2.

[0253] S6130: Terminal device 120 sends a measurement report of candidate cell 2 to DU1.

[0254] In response, DU1 receives the measurement report for candidate cell 2 from terminal device 120.

[0255] S6140:DU1 determines to switch terminal device 120 to candidate cell 2.

[0256] S6150:DU1 sends LTM command 1 to terminal device 120.

[0257] In response, terminal device 120 receives LTM command 1. LTM command 1 includes the identifier of the target cell.

[0258] S6160:DU1 sends signaling 1 to the CU.

[0259] In response, the CU receives signaling 1 from DU1. Signaling 1 contains information about the source serving cell's TA.

[0260] Optionally, signaling 1 may further include information about the TA of candidate cell 1.

[0261] More specifically, DU3 may send information about the TA of candidate cell 1 to DU1 by using CU.

[0262] Optionally, DU1 may determine the validity of the TA of the source serving cell by using a timing advance timer (TAT). Optionally, DU3 may also determine the validity of candidate cell 1 by using the TAT. TA You may judge the validity of this.

[0263] S6170:CU sends signaling 2 to DU2.

[0264] In response, DU2 receives signaling 2 from CU. Signaling 2 includes information about the source serving cell's TA and information about the candidate cell 1's TA.

[0265] S6180: Terminal device 120 sends an initial message to DU2.

[0266] In response, DU2 receives an initial message from terminal device 120. The initial message is the first message for switching to the target cell and is used to request access to the target cell. It includes the RRCReconfigurationComplete message, the cell-radio network temporary identifier (C-RNTI), or other content.

[0267] Furthermore, based on the initial message, DU2 determines that terminal device 120 has successfully accessed candidate cell 2.

[0268] S6190:DU2 sends an access success message to CU.

[0269] In response, CU receives an access success message from DU2.

[0270] Specifically, after DU2 determines that terminal device 120 has successfully switched to candidate cell 2, DU2 may send an access success message to CU that includes the identifier of the target cell. Furthermore, CU determines that terminal device 120 has successfully switched to candidate cell 2 based on the identifier of the target cell carried in the access success message.

[0271] After terminal device 120 switches to candidate cell 2, DU2, based on information about TA, decides not to perform random access procedures to the source serving cell and candidate cell 1 before the subsequent switch.

[0272] Furthermore, DU2 sends an LTM command to terminal device 120, where the LTM command includes the target cell identifier and instruction information 1. Based on the LTM command, terminal device 120 accesses the target cell using a random access channel-skip scheme and transmits uplink data based on the target cell's TA. For details of this part, please refer to the previous explanation.

[0273] Optionally, DU2 may receive further information regarding the TA of candidate cell 3. Based on the acquired information regarding the TA of candidate cell 3 (not shown in Figures 6A and 6B, but candidate cell 3 belongs to DU3), DU2 does not need to trigger terminal device 120 to initiate a random access procedure for the candidate cell from which the TA information was acquired. This reduces the amount of random access procedures that need to be initiated by terminal device 120.

[0274] In conclusion, DU2 may determine, based on the acquired TA information of the candidate cell, that it is not necessary to trigger terminal device 120 to initiate a random access procedure for the candidate cell from which the TA information was acquired. This effectively reduces the amount of random access procedures that need to be initiated by terminal device 120. Therefore, the power consumption of terminal device 120 and random access interference can be reduced. For an explanation of TA information, please refer to the explanation above. Further details will not be explained again here.

[0275] According to the technical solution described above, in this application, DU2 obtains information on the TA of multiple candidate cells from CU and determines that it is not necessary to trigger the terminal device 120 to initiate a random access procedure to the multiple candidate cells based on the information on the TA of the multiple candidate cells. Therefore, the number of random access procedures initiated by the terminal device 120 can be reduced, and the power consumption of the terminal device 120 can be reduced.

[0276] Note that the names of the above messages are merely used as examples for illustration and are not used as final limitations. Message names having similar or the same functions and used in future standards may be used. This is uniformly described in this specification. Details will not be described again below.

[0277] Note that some of the foregoing procedures are optional and may be unnecessary. For example, DU1 only instructs the terminal device 120 to send the contention-free random access preamble 1 to DU2, and does not instruct the terminal device 120 to send the contention-free random access preamble 2 to DU3. For example, DU1 only sends command 1 to the terminal device 120.

[0278] Note that the method 600 may be further applied to the scenario of interaction between base stations. For example, DU1 and CU belong to base station 1, and DU2 and DU3 belong to base station 2. For the method of interaction between base stations, refer to the method of interaction within the base station. Details will not be described again here.

[0279] When the method 600 is applied to the scenario of interaction between base stations, the names of the foregoing messages may be changed. For example, the UE context setup request message is changed to a HO (handover) request, and the UE context setup response message is changed to a HO response.

[0280] Figures 7A and 7B are schematic interaction flowcharts of a communication method 700 according to an embodiment of the present application. The method 700 may be executed by the terminal device 120, DU1, DU2, DU3, and CU, or may be executed by modules and / or components (such as chips or integrated circuits) installed in the terminal device 120, DU1, DU2, DU3, and CU and having corresponding functions. This is not limited in the embodiments of the present application. As shown in Figures 7A and 7B, the method 700 includes the following steps.

[0281] For S710 through S7150, please refer to the explanation for S610 through S6150. Further details will not be explained here.

[0282] S7160:CU sends request information to DU1.

[0283] In response, DU1 receives request information from CU, which is used to request that information about TA of at least one of the source serving cell and candidate cell 1 be obtained.

[0284] Optionally, DU1 may determine the validity of the source serving cell's TA by using TAT.

[0285] As an optional choice, DU3 can also use TAT to select candidate cell 1 TA You may judge the validity of this.

[0286] For S7170 through S7200, please refer to the explanation for S6160 through S6190. Further details will not be explained here.

[0287] After terminal device 120 is switched to candidate cell 2, DU2 does not need to trigger terminal device 120 to initiate a random access procedure to the source serving cell and candidate cell 1 based on information about TA. 120 When DU2 determines that the system has switched to candidate cell 1, it instructs terminal device 120 to access candidate cell 1 using the random access channel-skip method.

[0288] In response, DU2 sends an LTM command to terminal device 120, where the LTM command includes the identifier of the target cell for switching and instruction information 1. Based on the LTM command, terminal device 120 may access the target cell using a random access channel-skip scheme and send uplink data based on the TA of the target cell. See the previous explanation for details of this part.

[0289] For information regarding TA, please refer to the explanation above. Further details will not be provided here.

[0290] In Method 700, the present application is illustrated using an example in which the CU obtains information on the TA of at least one of the source serving cell and candidate cell 1 by transmitting request information to the DU1. However, the scenarios in which the CU transmits request information to the DU1 to obtain information on the TA of the source serving cell or the TA of candidate cell 1 are not limited.

[0291] According to the above technical solution, in this application, DU2 obtains information on the TA of multiple candidate cells from CU and determines that it is not necessary to trigger the terminal device 120 to initiate a random access procedure for the multiple candidate cells based on the information on the TA. Therefore, the number of random access procedures initiated by the terminal device 120 can be reduced, and the power consumption of the terminal device 120 can be reduced.

[0292] It should be noted that Method 700 can be further applied to scenarios involving communication between base stations. For example, DU1 and CU belong to base station 1, and DU2 and DU3 belong to base station 2. For methods of communication between base stations, please refer to the methods of communication within base stations. Details will not be explained again here.

[0293] When method 700 is applied to a scenario of interaction between base stations, the names of the aforementioned messages may be changed. For example, a UE context setup request message may be changed to an HO request, and a UE context setup response message may be changed to an HO response.

[0294] Figures 8A and 8B are schematic dialogue flowcharts of communication method 800 according to embodiments of the present application. Method 800 may be performed by terminal devices 120, DU1, DU2, DU3 and CU, or by modules and / or components (e.g., chips or integrated circuits) mounted on terminal devices 120, DU1, DU2, DU3 and CU and having corresponding functions. This is not limited to embodiments of the present application. As shown in Figures 8A and 8B, Method 800 includes the following steps:

[0295] For S810 through S8150, please refer to the explanation for S610 through S6150. Further details will not be explained here.

[0296] S8160: Terminal device 120 sends an initial message to DU2.

[0297] S8170:DU2 sends instruction information 2 to terminal device 120.

[0298] S8180: Terminal device 120 sends information about candidate cell 1's TA to DU2.

[0299] After terminal device 120 is switched to candidate cell 2, DU2 does not need to trigger terminal device 120 to initiate a random access procedure to the source serving cell and candidate cell 1 based on information about TA. 120 When DU2 determines that the system has switched to candidate cell 1, it instructs terminal device 120 to access candidate cell 1 using the random access channel-skip method.

[0300] Correspondingly, DU2 sends an LTM command to the terminal device 120, where the LTM command may include an identifier of a target cell for switching and an indication message 2. Based on the LTM command, the terminal device 120 determines to access the target cell in a random access channel - skip manner and may transmit uplink data based on the TA of the source serving cell or the TA of candidate cell 1. For the content of this part, please refer to the foregoing description. Details will not be described again here.

[0301] For the description of information related to TA, please refer to the foregoing description. Details will not be described again here.

[0302] S8190: DU2 sends an access success message to the CU.

[0303] In method 800, this application is described using an example where DU2 obtains information about the TA of candidate cell 1 from the terminal device 120 (alternatively, it may obtain information about the TA of the source serving cell). However, the scenario where DU2 obtains information about the TA of the serving cell from the terminal device 120 is not limited.

[0304] According to the above technical solution, in this application, DU2 obtains information about the TAs of a plurality of candidate cells from the terminal device 120 and determines that it is not necessary to trigger the terminal device 120 to start a random access procedure for the plurality of candidate cells based on the information about the TAs. Therefore, the amount of random access procedures initiated by the terminal device 120 can be reduced, and the power consumption of the terminal device 120 can be reduced.

[0305] Method 800 It should be noted that it may also be applicable to the scenario of interaction between base stations. For example, DU1 and CU belong to base station 1, and DU2 and DU3 belong to base station 2. For the method of interaction between base stations, please refer to the method of interaction within the base station. Details will not be described again here.

[0306] method 800 When this is applied to a scenario of communication between base stations, the names of the aforementioned messages may be changed. For example, a UE context setup request message may be changed to an HO request, and a UE context setup response message may be changed to an HO response.

[0307] The embodiments of the method in this application have been described above, and the embodiments of the corresponding apparatus will be described below.

[0308] To implement the functions of the methods provided in embodiments of this application, each terminal and network device may include a hardware structure and / or software module, and the functions may be implemented in the form of a hardware structure, a software module, or a combination of a hardware structure and a software module. Whether any of these functions are performed in the form of a hardware structure, a software module, or a combination of a hardware structure and a software module depends on the design constraints of the particular application and technical solution.

[0309] Figure 9 is a block diagram of a communication device 900 according to an embodiment of the present application. The communication device 900 may be a network device or terminal device as described in the above embodiment, or a chip or module within a network device or terminal device, and is configured to implement the method described in the above embodiment. The communication device 900 includes a transceiver module 910. The transceiver module 910 will be described below using an example.

[0310] The transceiver module 910 may include a transmitting module and a receiving module configured to implement the transmitting function or the receiving function in the embodiment of the method described above, respectively. The communication device 900 may further include a processing module configured to implement functions other than transmitting or receiving.

[0311] When the communication device 900 is configured to implement the functions of a network device, for example, the transceiver module 910 is configured to receive information about the TA of candidate cell 1, and the transceiver module 910 is further configured to transmit the identifier of the target cell 1 for switching, instruction information 1, etc., to the terminal device 120.

[0312] Optionally, the communication device 900 may further include a processing module 920. The processing module 920 is configured to perform functions other than the receiving and transmitting functions, for example, to determine instruction information 1.

[0313] Optionally, the communication device 900 further includes a storage module 930 (not shown in Figure 9). The storage module 930 is configured to store a program or code used to perform the method described above.

[0314] The content is used merely as an example for illustrative purposes. When the communication device 900 is configured to implement a network device, the communication device 900 is responsible for performing the methods or steps related to the network device in the embodiments of the methods described above.

[0315] The communication device 900 is a terminal device 120. For example, the transceiver module 910 is configured to report information about the TA of candidate cell 1 to the network device.

[0316] When the communication device 900 is a terminal device 120, it should be understood that the transceiver module 910 may be a module located within the control unit / subscriber unit / distributed unit of the terminal device 120 and configured to implement receiving and transmitting functions.

[0317] Optionally, the communication device 900 may further include a processing module 920. The processing module 920 is configured to perform functions other than receiving and transmitting, for example, to determine information regarding the TA of candidate cell 1.

[0318] Optionally, the communication device 900 further includes a storage module 930 (not shown in Figure 9). The storage module 930 is configured to store a program or code used to perform the method described above.

[0319] The content is used merely as an example for illustrative purposes. When the communication device 900 is configured to implement the functions of the terminal device 120, the communication device 900 is responsible for performing the methods or steps related to the terminal device 120 in the embodiments of the method described above.

[0320] Furthermore, for the implementation of each operation in Figure 9, please refer to the corresponding explanations in the embodiments of the method described above. Details will not be explained again here.

[0321] Figure 10 is a block diagram of a communication device 1000 according to an embodiment of the present application. The communication device 1000 includes a processor 1010 and a communication interface 1020. The processor 1010 and the communication interface 1020 can be connected to each other via a bus 1040 (not shown in Figure 10). The communication device 1000 can be configured to implement the functions of a terminal device, or it can be configured to implement the functions of a network device.

[0322] Optionally, the communication device 1000 further includes a memory 1030.

[0323] Memory 1030 includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), or compact disc read-only memory (CD-ROM). Memory is any other medium that can be configured to carry or store expected program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to such other medium. For example, memory 1030 is configured to store relevant instructions and data.

[0324] In embodiments of this application, the processor may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component that can implement or execute the methods, steps and logic block diagrams disclosed in embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the methods disclosed in relation to embodiments of this application may be completed directly by the hardware processor or by using a combination of hardware and software modules within the processor. For example, processor 1010 may be one or more central processing units (CPUs). When processor 1010 is a single CPU, the CPU may be a single-core CPU or a multi-core CPU.

[0325] When the communication device 1000 is configured to implement the functions of the terminal device 120, for example, the processor 1010 is configured to perform the following operations: determining information about the TA of candidate cell 1, and reporting information about the TA of candidate cell 1 to the network device.

[0326] The content is used merely as an example for illustrative purposes. When the communication device 1000 is configured to implement the functions of the terminal device 120, the communication device 1000 is responsible for performing the methods or steps related to the terminal device 120 in the embodiments of the method described above.

[0327] When the communication device 1000 is configured to implement the functions of a network device, for example, the processor 1010 is configured to perform the following operations: receiving information about the TA of candidate cell 1 and sending the identifier of the target cell 1 for switching and instruction information 1 to the terminal device 120.

[0328] The content is used merely as an example for illustrative purposes. When the communication device 1000 is configured to implement the functions of a network device, the communication device 1000 is responsible for performing the methods or steps related to the network device in the embodiments of the methods described above.

[0329] The above description is merely an example for illustrative purposes. For specific details, please refer to the descriptions in the embodiments of the method. In addition, for the implementation of each operation in Figure 10, please refer to the corresponding descriptions in the embodiments of the method shown in Figure 3.

[0330] The communication device shown in Figures 9 and 10 is configured to implement the features described in the embodiments of the method described above. Therefore, for specific execution steps and methods of the communication device shown in Figures 9 and 10, please refer to the features described in the embodiments of the method described above.

[0331] It should be understood that the transceiver module described above may include a transmit module and a receive module. The transmit module is configured to perform the transmit operation of the communication device, and the receive module is configured to perform the receive operation of the communication device. For the sake of clarity, the transmit module and the receive module are combined into a single transceiver module in the embodiments of this application. Hereinafter, a unified explanation is provided. Further details will not be described again below.

[0332] figure 11 This is a diagram of a communication device 1100 according to an embodiment of the present application. The communication device 1100 may be configured to implement the functions of a network device or terminal device in the method described above. The communication device 1100 may also be a chip within a network device or terminal device. The communication device 1100 includes an input / output interface 1120 and a processor 1110. The input / output interface 1120 may also be an input / output circuit. The processor 1110 may be a signal processor, chip, or other integrated circuit capable of implementing the method of the present application. The input / output interface 1120 is configured to input or output signals or data.

[0333] For example, the communication device 1100 is a terminal device 120, and the input / output interface 1120 is configured to report information about the candidate cell 1's TA to the network device. 1110 The processor is configured to determine information about the TA of candidate cell 1. 1110 It is further configured to perform some or all of the steps of any method provided in this application.

[0334] For example, the communication device 1100 is a network device, and the input / output interface 1120 is configured to transmit the identifier of the target cell 1 for switching, instruction information 1, etc., to the terminal device 120.

[0335] In possible implementations, the processor 1110It executes instructions stored in memory to implement functions implemented by the terminal device 120 or network device.

[0336] Optionally, the communication device 1100 further includes memory. Optionally, the processor and memory are integrated together. Optionally, the memory is located outside the communication device 1100.

[0337] In possible implementations, the processor 1110 This may be a logic circuit, and a processor 1110 The input / output interface 1120 inputs / outputs messages or signaling. The logic circuit may be a signal processor, chip, or other integrated circuit that can implement the method in the embodiments of this application.

[0338] The above description of the communication device 1100 in Figure 11 is merely an example for illustrative purposes. The communication device 1100 can be configured to perform the method in the above-described embodiment. For specific details, please refer to the description of the embodiment of the method above. Details will not be explained again here.

[0339] Figure 12 is a block diagram of a communication device 1200 according to an embodiment of the present application. The communication device 1200 may be a network device or a chip. The communication device 1200 may be configured to perform the operations described above, which are performed by the network device.

[0340] When the communication device 1200 is a network device, such as a base station, Figure 12 shows a simplified structure of the base station. The base station includes modules 1210, 1220, and 1230. Module 1210 is mainly configured to perform baseband processing and control the base station. Module 1210 is usually the control center of the base station and is sometimes called a processor, and in the embodiment of the method described above, it is configured to control the base station to perform processing operations on the network device side. Module 1220 is mainly configured to store computer program code and data. Module 1230 is mainly configured to transmit and receive radio frequency signals and to convert radio frequency signals to baseband signals. Module 1230 is usually called a transceiver module, transceiver circuit, transceiver, etc. The transceiver module within module 1230 is sometimes called a transceiver, etc., and includes an antenna 1233 and a radio frequency circuit (not shown in Figure 12), where the radio frequency circuit is mainly configured to perform radio frequency processing. Optionally, components configured to implement receiving functionality and located within module 1230 may be considered receivers, and components configured to implement transmitting functionality may be considered transmitters. In other words, module 1230 includes receiver 1232 and transmitter 1231. Receivers may also be referred to as receiving modules, receiving devices, receiver circuits, etc., and transmitters may also be referred to as transmitting modules, transmitting devices, transmitter circuits, etc.

[0341] Modules 1210 and 1220 may each include one or more boards, each board may include one or more processors and one or more memories. The processors are configured to read and execute programs from memory, implement baseband processing functions, and control base stations. Furthermore, if multiple boards exist, they may be interconnected to improve processing capabilities. In any implementation, multiple boards may share one or more processors, multiple boards may share one or more memories, or multiple boards may simultaneously share one or more processors.

[0342] In one implementation, the transceiver module within module 1230 is configured to execute the transceiver-related processes performed by the network device in the embodiments shown in Figures 4 to 8B. The processor within module 1210 is configured to execute the processing-related processes performed by the network device in the embodiments shown in Figures 4 to 8B.

[0343] In another implementation, the processor within module 1210 is configured to execute processing-related processes performed by the network device in the embodiments shown in Figures 4 to 8B.

[0344] In another implementation, the transceiver module within module 1230 is configured to perform the transceiver-related processes that are performed by the network device in the embodiments shown in Figures 4 to 8B.

[0345] Figure 12 is merely an example, not an exhaustive one, and it should be understood that the aforementioned access network devices, including processors, memory, and transceivers, may not depend on the configurations shown in Figures 9-11.

[0346] When the communication device 1200 is a chip, the chip includes a transceiver, memory, and a processor. The transceiver may be an input / output circuit or a communication interface. The processor is a processor, a microprocessor, or an integrated circuit on the chip. In embodiments of the above-described method, the transmission operation performed by the network device may be understood as an output of the chip, and the reception operation performed by the network device in embodiments of the above-described method may be understood as an input of the chip.

[0347] Figure 13 is a block diagram of a communication device 1300 according to an embodiment of the present application. The communication device 1300 may be a terminal device, a processor or chip of a terminal device. The communication device 1300 may be configured to perform operations performed by the terminal device in the embodiment of the method described above.

[0348] When the communication device 1300 is a terminal device, Figure 13 shows a simplified structure of the terminal device. As shown in Figure 13, the terminal device includes a processor, memory, and a transceiver. The memory may store computer program code. The transceiver includes a transmitter 1331, a receiver 1332, a radio frequency circuit (not shown in Figure 13), an antenna 1333, and an input / output device (not shown in Figure 13).

[0349] The processor is primarily configured to process communication protocols and data, control terminal devices, execute software programs, and process data within those software programs. Memory is primarily configured to store software programs and data. Radio frequency circuits are configured to perform conversions between baseband signals and radio frequency signals and to process radio frequency signals. Antennas are primarily configured to transmit and receive radio frequency signals in the form of electromagnetic waves. Input / output devices, such as touchscreens, displays, or keyboards, are primarily configured to receive data entered by the user and output data to the user. Note that some types of terminal devices may not have input / output devices.

[0350] When data needs to be transmitted, the processor performs baseband processing on the data to be transmitted, then outputs the baseband signal to a radio frequency circuit. The radio frequency circuit then performs radio frequency processing on the baseband signal and transmits the radio frequency signal externally in the form of electromagnetic waves via an antenna. When data is transmitted to a terminal device, the radio frequency circuit receives the radio frequency signal via the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor. The processor converts the baseband signal into data and processes the data. For ease of explanation, Figure 13 simply shows one memory, one processor, and one transceiver. Actual terminal device products may have one or more processors and one or more memories. Memory may also be called a storage medium, storage device, etc. Memory may be located independently of the processor or may be integrated with the processor. This is not limited to the embodiments of this application.

[0351] In the embodiments of this application, the antenna and radio frequency circuit having transmitting and receiving functions may be considered as transceiver modules of a terminal device, and the processor having processing functions may be considered as a processing module of a terminal device.

[0352] As shown in Figure 13, the terminal device includes a processor 1310, a memory 1320, and a transceiver 1330. The processor 1310 may also be called a processing unit, processing board, processing module, or processing device, and the transceiver 330 may also be called a transceiver unit or transceiver device.

[0353] Optionally, a component located within the transceiver 1330 and configured to implement a receiving function may be considered a receiving module, and a component located within the transceiver 1330 and configured to implement a transmitting function may be considered a transmitting module. In other words, the transceiver 1330 includes a receiver and a transmitter. The transceiver is sometimes also called a transceiver module, transceiver circuit, etc. The receiver is sometimes also called a receiving module, receiver circuit, etc. The transmitter is sometimes also called a transmitting module, transmitter circuit, etc.

[0354] For example, in one implementation, the processor 1310 is configured to perform the processing operations on the terminal device side in the embodiments shown in Figures 4 to 8B, and the transceiver 1330 is configured to perform the transmission and reception operations on the terminal device side in Figures 4 to 8B.

[0355] Please understand that Figure 13 is merely an example, not an exhaustive one. It includes a transceiver module and a processing module. terminal The device does not have to depend on the configuration shown in Figures 9 to 11.

[0356] When the communication device 1300 is a chip, the chip includes a processor, memory, and a transceiver. The transceiver may be an input / output circuit or a communication interface. The processor may be a processing module, a microprocessor, or an integrated circuit on the chip. In the embodiments of the above method, a transmission operation performed by the terminal device may be understood as an output of the chip, and a reception operation performed by the terminal device in the embodiments of the above method may be understood as an input of the chip.

[0357] This application further provides a chip including a processor configured to call instructions from memory and execute instructions stored in memory, thereby enabling a communication device on which the chip is mounted to perform the method described in the above-described embodiment.

[0358] This application provides another chip including an input interface, an output interface, and a processor. The input interface, output interface, and processor are connected via an internal connection path. The processor is configured to execute code in memory, and once the code is executed, the processor is configured to perform the method described in the above embodiment. Optionally, the chip further includes memory, which is configured to store a computer program or code.

[0359] This application provides a processor configured to be coupled to memory and to perform the functions of the method and network device or terminal device in any one of the embodiments described above.

[0360] Another embodiment of this application provides a computer program product including instructions. When the computer program product is executed on a computer, the method in the above-described embodiment is implemented.

[0361] This application further provides a computer program. When the computer program is executed on a computer, the method in the above-described embodiment is implemented.

[0362] Another embodiment of this application provides a computer-readable storage medium for storing a computer program. When the computer program is executed by a computer, the method of the above-described embodiment is implemented.

[0363] This application further provides a communication system. The communication system includes a network device 110, terminal The network includes device 120 and core network elements. The network device 110 is configured to perform the method described above. terminal Device 120 is configured to perform the method described above, and core network element 130 is configured to perform the method described above. For a specific explanation, please refer to the previous explanation. Further details will not be explained again here.

[0364] In the description of embodiments of this application, unless otherwise specified, “multiple” means two or more. “At least one of the following items (parts)” or similar expressions mean any combination of these items, including a single item (part) or any combination of multiple items (parts). For example, at least one item (piece) of a, b, or c may be a, b, c, a and b, a and c, b and c, or a, b and c, where a, b, and c may be singular or plural.

[0365] In addition, in the embodiments of this application, in order to clearly illustrate the technical solutions in the embodiments of this application, terms such as “First” and “Second” are used to distinguish the same or similar items that provide essentially the same function or purpose. Those skilled in the art will understand that terms such as “First” and “Second” do not limit the quantity or execution sequence, and that terms such as “First” and “Second” do not indicate a clear difference. In addition, in the embodiments of this application, words such as “Example” or “For example” are used to indicate an example, illustration, or explanation.

[0366] In the description of embodiments of this application, unless otherwise specified, " / " represents an "or" relationship between related objects. For example, A / B may represent A or B. In this application, "and / or" merely describes a relationship between related objects, indicating that three relationships may exist. For example, A and / or B may represent the following three cases: only A exists, both A and B exist, or only B exists, where A and B may be singular or plural.

[0367] The sequence numbers of the processes described above do not imply the execution order in the embodiments of this application. The execution order of the processes should be determined based on the function and internal logic of the processes and should not be construed as any limitation on the implementation processes of the embodiments of this application.

[0368] Those skilled in the art will recognize that the units and algorithmic steps can be implemented by electronic hardware, or by a combination of computer software and electronic hardware, in combination with the examples described in the embodiments disclosed herein. Whether the functions are performed by hardware or software depends on the specific application and the design constraints of the technical solution. Those skilled in the art may use different methods to implement the functions described for each specific application, and such implementations should not be considered beyond the scope of this application.

[0369] For the sake of convenience and concise explanation, it will be readily apparent to those skilled in the art that the detailed operating processes of the aforementioned systems, devices, and units can be described by referring to the corresponding processes in the embodiments of the methods described above. Further details will not be described here.

[0370] In some embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods may be implemented in other ways. For example, the embodiments of the apparatus described are merely examples. For example, the division into units is merely a logical functional division, and in actual implementation, other divisions may be used. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or performed.

[0371] In addition, mutual coupling, direct coupling, or communication connection described or discussed may be implemented through several interfaces. Indirect coupling or communication connection between devices or units may be implemented electronically, mechanically, or in other forms.

[0372] Units described as separate parts may or may not be physically separate, and parts shown as units may or may not be physical units; in other words, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solution of the embodiment.

[0373] In addition, the functional units in the embodiments of this application may be integrated into a single processing unit, or each unit may exist physically independently, or two or more units may be integrated into a single unit.

[0374] When functions are implemented in the form of software function units and sold or used as independent products, these functions may be stored on a computer-readable storage medium. Based on this understanding, the technical solutions in the embodiments of this application may be implemented in the form of a software product, either essentially or in part with respect to the prior art, or in part with respect to the technical solutions. The computer software product is stored on a storage medium and includes several instructions for instructing a computer device (which may be a personal computer, server, network device, etc.) to perform all or part of the steps of the method in the embodiments of this application. The storage medium mentioned above includes any medium capable of storing program code, such as a USB flash drive, removable hard disk, ROM, RAM, magnetic disk, or optical disk.

[0375] The embodiments of this application may be cross-referenced. Unless otherwise specified or unless a logical inconsistency arises, the terminology and / or descriptions in different embodiments are consistent and may be cross-referenced, and technical features in different embodiments may be combined into new embodiments based on the internal logical relationships between the technical features.

[0376] In embodiments of this application, it can be understood that a terminal device, an access network device, or a core network device may perform some or all of the steps in embodiments of this application. These steps or actions are merely examples. In embodiments of this application, other actions or various variations of actions may be performed further. In addition, the steps may be performed in an order different from that shown in embodiments of this application, and not all of the actions in embodiments of this application may be performed.

Claims

1. A communication method, the method is applied to an L1 / L2 triggered mobility LTM, the method is applied to a terminal device or a chip within the terminal device, the method is The steps include determining information regarding the timing advance TA of the first candidate cell, The steps include reporting the information regarding the TA of the first candidate cell to the first network device, Methods that include...

2. This method is The process further includes the step of receiving instruction information, wherein the instruction information instructs to report information regarding the TA of a candidate cell, and the candidate cell includes the first candidate cell. The method according to claim 1.

3. The information relating to the TA of the first candidate cell is The TA of the first candidate cell, or Instruction information indicating that the TA of the first candidate cell is valid, or The remaining effective time of the TA of the first candidate cell, or The time offset of the TA of the first candidate cell, The time offset includes at least one of the following, wherein the time offset corresponds to the period of the TA of the first candidate cell. The method according to claim 1 or 2.

4. The step of receiving the instruction information is: A step of receiving the instruction information and the identifier of the target cell for switching from a second network device, wherein the target cell is a second candidate cell, and the second candidate cell belongs to the first network device, or The step of receiving the instruction information from the first network device, The method according to claim 2 or 3, including the method described in claim 2 or 3.

5. The second candidate cell is different from the first candidate cell. The method according to claim 4.

6. The instruction information instructs to report the information relating to the TA of the first candidate cell. The method according to any one of claims 2 to 5.

7. The first candidate cell does not belong to the first network device. The method according to any one of claims 1 to 6.

8. A communication method, which is applied to an L1 / L2 triggered mobility LTM. A step of receiving information regarding the timing advance TA of a first candidate cell by a first network device, wherein the first candidate cell does not belong to the first network device, The first network device transmits an identifier of the target cell for switching and first instruction information to a terminal device, wherein the first instruction information instructs the terminal device to access the target cell using a random access channel-skip scheme, and the target cell is the first candidate cell. Methods that include...

9. The step of receiving the information relating to the TA of the first candidate cell by the first network device is: The first network device receives the information relating to the TA of the first candidate cell from the terminal device, or The first network device receives the information relating to the TA of the first candidate cell from the second network device. The method according to claim 8, including the method described in claim 8.

10. This method is The first network device further includes the step of transmitting second instruction information to the terminal device, The second instruction information instructs to report information regarding the TA of the candidate cell, or The second instruction information instructs to report information regarding the TA of the first candidate cell. The method according to claim 9.

11. This method is The first network device further includes the step of transmitting request information to the second network device, wherein the request information is used to request the information relating to the TA of the first candidate cell. The method according to claim 9 or 10.

12. The information relating to the TA of the first candidate cell is The TA of the first candidate cell, or Instruction information indicating that the TA of the first candidate cell is valid, or The remaining effective time of the TA of the first candidate cell, or The time offset of the TA of the first candidate cell, The time offset includes at least one of the following, wherein the time offset corresponds to the period of the TA of the first candidate cell. The method according to any one of claims 8 to 11.

13. A communication method, which is applied to an L1 / L2 triggered mobility LTM. A first network device transmits first instruction information to a terminal device, wherein the first instruction information instructs the terminal device to acquire information regarding the TA of a first candidate cell. The first network device transmits an identifier of the target cell for switching and second instruction information to the terminal device, wherein the target cell is a second candidate cell, and the second candidate cell belongs to the second network device. Includes, The second instruction information instructs the second network device to report the information regarding the timing advance TA of the first candidate cell, and the first candidate cell does not belong to the second network device. method.

14. The information relating to the TA of the first candidate cell is The TA of the first candidate cell, or Instruction information indicating that the TA of the first candidate cell is valid, or The remaining effective time of the TA of the first candidate cell, or The time offset of the TA of the first candidate cell, The time offset includes at least one of the following, wherein the time offset corresponds to the period of the TA of the first candidate cell. The method according to claim 13.

15. The second candidate cell is different from the first candidate cell. The method according to claim 13 or 14.

16. A communication method, which is applied to an L1 / L2 triggered mobility LTM. A step of obtaining information regarding the timing advance TA of a first candidate cell using a first network device, wherein the first candidate cell belongs to the first network device or a third network device, and the information regarding the TA of the first candidate cell is used to determine whether to use a random access channel-skip scheme. The first network device transmits the information relating to the TA of the first candidate cell to the second network device by using the fourth network device, Methods that include...

17. The step of obtaining the information relating to the TA of the first candidate cell by the first network device is: The first network device receives the information relating to the TA of the first candidate cell from the fourth network device, or The first network device receives a contention-free random access preamble transmitted by a terminal device in the first candidate cell, and The first network device determines the information relating to the TA of the first candidate cell based on the contention-free random access preamble. The method according to claim 16, including the method described in claim 16.

18. This method is The first network device further includes the step of receiving request information from the fourth network device, wherein the request information is used to request the information relating to the TA of the first candidate cell. The method according to claim 17.

19. The information relating to the TA of the first candidate cell is The TA of the first candidate cell, or Instruction information indicating that the TA of the first candidate cell is valid, or The remaining effective time of the TA of the first candidate cell, or The time offset of the TA of the first candidate cell, The time offset includes at least one of the following, wherein the time offset corresponds to the period of the TA of the first candidate cell. The method according to any one of claims 16 to 18.

20. A communication device comprising a processor, wherein the processor is configured to enable the communication device to perform the method described in any one of claims 1 to 19 by executing a computer program or instruction, or via a logic circuit.

21. The communication device according to claim 20, further comprising a memory, wherein the memory is configured to store the computer program or the instruction.

22. The communication device further comprises a communication interface, the communication interface is configured to input and / or output signals. The communication device according to claim 20 or 21.

23. A communication device comprising a logic circuit and an input / output interface, A communication device wherein the input / output interface is configured to input and / or output signals, and the logic circuit is configured to perform the method according to any one of claims 1 to 19.

24. A computer-readable storage medium, wherein the computer-readable storage medium stores a computer program or instruction, and when the computer program or instruction is executed on a computer, the method according to any one of claims 1 to 19 is executed.

25. A computer program product comprising instructions, wherein when the instructions are executed on a computer, the method according to any one of claims 1 to 19 is executed.

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