Communication method and communication apparatus

Abstract

The application provides a communication method and a communication device. In the communication method provided by the application, the remaining time of the first TAT when a terminal switches to a first cell is indicated to a second DU, so that the second DU can learn the remaining valid time of the first TA, and the second DU can send a new TAC to the terminal before the first TA expires, so as to ensure the uplink synchronization between the terminal and the second DU.

Description

Technical Field

[0001] This application relates to the field of communications, and more particularly to a communication method and a communication device. Background Technology

[0002] With the development of mobile communication technology, conditional L1 / L2 triggered mobility (CLTM) cell handover technology has been proposed, or simply CLTM handover. In the CLTM handover process, when the terminal determines that the target cell meets the CLTM handover conditions, the terminal performs a handover to the target cell. CLTM handover conditions include, for example, that the signal quality of the target cell is better than that of the serving cell, or that the beam pattern of the target cell is better than that of the current serving cell.

[0003] However, after the terminal switches to the target cell based on the CLTM handover method, it may experience uplink synchronization issues, which may affect the transmission of uplink data. Summary of the Invention

[0004] This application provides a communication method and a communication device to avoid uplink synchronization problems that may occur after a terminal switches to a target cell.

[0005] Firstly, this application provides a communication method that can be applied to the terminal side, such as a terminal or a communication module within a terminal, or a circuit or chip (such as a modem chip, also known as a baseband chip, or a system-on-chip (SoC) chip containing a modem core, or a system-in-package (SIP) chip) responsible for communication functions within the terminal. In this application, a terminal is used as an example for description.

[0006] The communication method includes: receiving first information from a first distributed unit (DU), the first information indicating the timing advance (TA) used by the terminal when handing over to a first cell, the first cell belonging to a second DU; starting a first time alignment timer (TAT) corresponding to the first TA; and sending second information indicating the remaining time of the first TAT.

[0007] In this application, the first DU refers to the DU of the cell to which the terminal accesses before performing CLTM handover. The second DU refers to the DU of the first cell to which the terminal accesses after performing CLTM handover.

[0008] In this application, the central unit (CU) to which the first DU belongs is also referred to as the first CU, and the CU to which the second DU belongs is also referred to as the second CU. In one example, the first CU and the second CU are the same CU. In another example, the first CU and the second CU are different.

[0009] Understandably, the first TAT will start timing after the first TAT corresponding to the first TA is started.

[0010] In the communication method provided by the first aspect, after the terminal starts the first TAT, the terminal can send second information to indicate the remaining time of the first TAT, that is, the terminal can report the remaining time of the first TAT.

[0011] Regarding how the terminal sends the second information indicating the remaining time of the first TAT, there are two different implementation methods:

[0012] The first implementation involves the terminal carrying the second information within the first uplink message; wherein the first uplink message is the uplink message sent by the terminal to the first cell after the terminal accesses the first cell. In other words, in this first implementation, after the terminal accesses the first cell, it carries the second information indicating the remaining time of the first TAT in the first uplink message sent to the first cell, thereby enabling the second DU to know the remaining time of the first TAT.

[0013] The second implementation involves the terminal carrying the second information in a first cell handover notification sent to the first DU. This first cell handover notification indicates that the terminal is about to hand over to the first cell. In other words, in this second implementation, when the terminal determines it needs to hand over to the first cell, it carries the second information indicating the remaining time of the first TAT in the first cell handover notification sent to the first DU. Upon receiving the second information, the first DU can forward it to the second DU via the first CU and the second CU, thus allowing the second DU to know the remaining time of the first TAT. It is understandable that when the first CU and the second CU are the same CU, the forwarding of the second information by the first DU to the second DU via the first CU and the second CU can also be described as: the first DU forwards the second information to the second DU via the first CU / second CU.

[0014] Understandably, once the second DU learns of the remaining time of the first TAT, the second DU can determine how long the first TAT has been running based on the remaining time of the first TAT, thereby determining how long the first TA has been valid. Furthermore, the second DU can determine how long the validity period of the terminal's first TA is left based on the duration of the first TA's validity (also known as the remaining validity time of the first TA), so that the second DU can send a new TAC to the terminal before the first TA expires, in order to ensure uplink synchronization between the terminal and the second DU.

[0015] In this application, when the terminal carries the second information in the first cell handover notification sent to the first DU, in one possible implementation, the method further includes: if no acknowledgment message is received from the first DU, retransmitting the first cell handover notification, wherein the acknowledgment message is used to indicate that the first DU has successfully received the first cell handover notification.

[0016] Understandably, when the terminal carries the second information in the first cell handover notification sent to the first DU, if the first DU fails to receive the first cell handover notification from the terminal, there is a problem that the first DU cannot indicate the second information used to indicate the remaining time of the first TAT to the second DU. Therefore, to solve this problem, in this implementation, after the terminal sends the first cell handover notification, if the terminal does not receive an acknowledgment message from the first DU, the terminal will retransmit the first cell handover notification, thereby ensuring that the first DU receives the second information used to indicate the remaining time of the first TAT, and then forward the second information to the second DU through the first CU and the second CU. Similarly, it is understandable that when the first CU and the second CU are the same CU, forwarding the second information to the second DU through the first CU and the second CU can also be described as: indicating the second information to the second DU through the first CU / second CU.

[0017] In this application, there are different ways to implement the first TAT:

[0018] For example, in one implementation of the first TAT, the first TAT is the TAT corresponding to the primary timing advance group (PTAG) to which the first cell belongs after the terminal hands over to the first cell. Specifically, the second DU can forward the TAT corresponding to the PTAG to which the first cell belongs to to the first DU via the second CU and the first CU, thus enabling the first DU to know the TAT corresponding to the PTAG to which the first cell belongs. Furthermore, the first DU can configure the TAT corresponding to the PTAG to which the first cell belongs to to the terminal via RRC signaling, so that the terminal knows the TAT corresponding to the PTAG to which the first cell belongs. In other words, in this first implementation, the terminal starts timing based on the TAT corresponding to the PTAG to which the first cell belongs after receiving the first TA.

[0019] For example, in the second implementation of the first TAT, the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG. That is, for the same first TA, it can be considered that there are two TATs: one is the first TAT, and the other is the TAT corresponding to the PTAG of the first cell. The first TAT being a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG of the first cell can also be described as: the first TAT is a TAT generated by the first DU or the second DU that is independent of the TAT corresponding to the PTAG of the first cell. For example, the duration of the first TAT is 200 milliseconds, and the duration of the TAT corresponding to the PTAG of the first cell is 500 milliseconds. Based on this second implementation, it is possible to flexibly configure different durations of the first TAT for the terminal according to different scenarios. For example, if the terminal is currently in a high-speed scenario (e.g., a high-speed rail scenario), but the timing duration of the TAT corresponding to the PTAG of the first cell may be set to a relatively long value, then the TAT corresponding to the PTAG of the first cell may not be suitable for the current handover scenario. In this case, a first TAT with a shorter duration can be configured for the terminal.

[0020] In one possible implementation, if the first TAT corresponds to the PTAG of the first cell, the method further includes resetting the media access control (MAC) layer during the handover to the first cell without stopping the operation of the first TAT. In this implementation, the first TAT continues to run during the handover process to the first cell, ensuring that the terminal continues to know the remaining effective time of the first TA based on the first TAT.

[0021] In one possible implementation, if the first TAT is a different TAT generated by the first DU or the second DU than the TAT corresponding to the PTAG, the MAC layer is reset and the operation of the first TAT is stopped during the handover to the first cell. Further, the terminal can start the TAT corresponding to the PTAG by sending a second uplink message to the second DU, or after successfully establishing a connection with the second DU, or when the first TAT is stopped or the MAC layer is reset. In this implementation, after the terminal stops the operation of the first TAT, it determines the remaining effective time of the first TA through the TAT corresponding to the PTAG.

[0022] In conjunction with the first aspect, in one possible implementation, the method further includes: receiving a radio resource control (RRC) message from a first CU, the RRC message indicating a first threshold value or a second threshold value; if the time the first TAT has been running is greater than or equal to the first threshold value, or if the remaining time of the first TAT is less than the second threshold value, sending third information to a first DU; wherein the third information is used to request the first DU to indicate the RA preamble used when performing uplink synchronization with the first cell, or the third information is used to request the first DU to send a time advance command (TAC).

[0023] Understandably, if the time that the first TAT has been running is greater than or equal to the first threshold, or if the remaining time of the first TAT is less than the second threshold, it means that the remaining effective time of the first TA may be very small, that is, the first TA may be about to expire.

[0024] Understandably, if the first TA fails, the terminal cannot establish a connection with the first cell through the LTM no-random access procedure. Therefore, in this implementation, the terminal sends third information to the first DU before the first TA fails, thereby enabling the terminal to reacquire the TAC (carrying a new TA, for example, called the second TA) and restart the first TAT to restart the timing, thus avoiding the inability to perform the LTM no-random access procedure.

[0025] Optionally, in this application, when the first DU sends first information to the terminal to indicate the first TA used when the terminal switches to the first cell, the first information may include information indicating the first TAG, where the first TAG is the TAG to which the first cell belongs. In this implementation, the first TAT corresponding to the first TA can also be considered as the TAT corresponding to the first TAG.

[0026] Optionally, when the first information includes information for indicating the first TAG, the second information may also include information for indicating the first TAG.

[0027] Secondly, this application provides a communication method that can be applied to the network side, such as a first DU or a communication module within the first DU, or a circuit or chip (such as a modem chip, also known as a baseband chip, or a system-on-chip (SoC) chip containing a modem core, or a system-in-package (SIP) chip) responsible for communication functions within the first DU. In this application, the first DU is used as an example for description.

[0028] The communication method includes: sending first information to a terminal, the first information indicating a first TA used by the terminal when handing over to a first cell, the first cell belonging to a second DU; and sending second information, the second information including the remaining time of a first TAT corresponding to the first TA when the terminal handovers to the first cell.

[0029] In the communication method provided by the second aspect, the first DU can send second information to indicate the remaining time of the first TAT, which can be understood as the first DU being able to report the remaining time of the first TAT.

[0030] There are different implementations for how the first DU sends the second information to indicate the remaining time of the first TAT.

[0031] For example, in implementation a): After receiving a first cell handover notification from the terminal, the first DU sends second information. The first cell handover notification indicates that the terminal is about to hand over to the first cell, and the second information is carried in the first cell handover notification. That is, in this first implementation, the terminal carries the second information in the first cell handover notification sent to the first DU; correspondingly, after receiving the second information in the first cell handover notification, the first DU forwards the second information to the second DU through the first CU and the second CU, so that the second DU can know the remaining time of the first TAT. It is understandable that when the first CU and the second CU are the same CU, forwarding the second information to the second DU through the first CU and the second CU can also be described as: instructing the second information to the second DU through the first CU / second CU.

[0032] For example, when sending the first information to the terminal, the first DU also initiates the first TAT corresponding to the first TA. Furthermore, the first DU sending second information indicating the remaining time of the first TAT can be implemented in the following ways: b) and c).

[0033] Implementation method b): The first DU sends the second information, including: after receiving the second cell handover notification from the terminal, sending the second information based on the activated first TAT. The second cell handover notification is used to indicate that the terminal is about to hand over to the first cell. That is, in this implementation method b), the first DU also activates the first TAT corresponding to the first TA. Then, when the first DU receives the second cell handover notification from the terminal indicating that the terminal is about to hand over to the first cell, the first DU will forward the remaining time of its activated first TAT to the second DU through the first CU and the second CU.

[0034] Implementation method c): The first DU sends second information, including: after receiving the fourth information, sending the second information based on the started first TAT, the fourth information is used to request the remaining time of the first TAT corresponding to the first TA. Specifically, the fourth information is sent by the second CU to the first DU through the first CU. It can be understood that when the second CU and the first CU are the same CU, the fourth information is sent by the second CU to the first DU through the first CU, or alternatively described as the fourth information being sent by the second CU / first CU to the first DU. That is to say, in this implementation method c), the first DU also starts the first TAT corresponding to the first TA, and then the second CU requests the first DU to send the remaining time of the first TAT corresponding to the first TA through the first CU. Correspondingly, after receiving the request, the first DU forwards the remaining time of the first TAT it started to the second DU through the first CU and the second CU.

[0035] Understandably, in implementations b) and c), when the second CU and the first CU are the same CU, after receiving the request, the first DU forwards the remaining time of the first TAT it started to the second DU through the first CU and the second CU. Alternatively, it can be described that after receiving the request, the first DU forwards the remaining time of the first TAT it started to the second DU through the first CU / second CU.

[0036] Understandably, once the second DU learns of the remaining time of the first TAT, the second DU can determine how long the first TAT has been running based on the remaining time of the first TAT, thereby determining how long the first TA has been valid. Furthermore, the second DU can determine how long the validity period of the terminal's first TA is left based on the duration of the first TA's validity (also known as the remaining validity time of the first TA), so that the second DU can send a new TAC to the terminal before the first TA expires, in order to ensure uplink synchronization between the terminal and the second DU.

[0037] Optionally, the second DU can indicate the absolute time for generating the first TA to the first DU via the first CU and the second CU. Understandably, when the first CU and the second CU are the same CU, the second DU indicating the absolute time for generating the first TA to the first DU via the first CU and the second CU can also be described as the second DU indicating the absolute time for generating the first TA to the first DU via the first CU / second CU. Furthermore, the first information sent by the first DU to the terminal can also carry the absolute time for the second DU to generate the first TA. For example, the absolute time for the second DU to generate the first TA is Coordinated Universal Time (UTC). In this way, when the terminal receives the first information, it can determine how long the first TA has been valid based on the absolute time for the second DU to generate the first TA and the time of the currently received first TA. Then, when starting the first TAT timing, it starts timing from time 1, where the interval between time 1 and the initial time of the first TAT is the time the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved.

[0038] Thirdly, this application provides a communication method that can be applied to the network side, such as a second DU or a communication module within the second DU, or a circuit or chip (such as a modem chip, also known as a baseband chip, or a system-on-chip (SoC) chip containing a modem core, or a system-in-package (SIP) chip) within the second DU responsible for communication functions. In this application, the first DU is used as an example for description.

[0039] The communication method includes: instructing a first TA to a first DU when the terminal switches to a first cell, the first cell belonging to a second DU; and receiving second information, the second information being used to indicate the remaining time of the first TAT corresponding to the first TA when the terminal switches to the first cell.

[0040] Understandably, once the second DU learns of the remaining time of the first TAT, the second DU can determine how long the first TAT has been running based on the remaining time of the first TAT, thereby determining how long the first TA has been valid. Furthermore, the second DU can determine how long the validity period of the terminal's first TA is left based on the duration of the first TA's validity (also known as the remaining validity time of the first TA), so that the second DU can send a new TAC to the terminal before the first TA expires, in order to ensure uplink synchronization between the terminal and the second DU.

[0041] In conjunction with the third aspect, in one possible implementation, receiving the second information includes: receiving a first uplink message from the terminal, wherein the first uplink message carries the second information; the first uplink message is an uplink message sent by the terminal to the first cell after the terminal accesses the first cell.

[0042] In conjunction with the third aspect, in one possible implementation, the first TAT is the TAT corresponding to the PTAG of the first cell after the terminal switches to the first cell; or, the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG.

[0043] When the first TAT is generated by the second DU, the second DU can indicate the generated first TAT to the first DU through the second CU and the first CU.

[0044] Fourthly, this application provides a communication method that can be applied to the terminal side, such as a terminal or a communication module within a terminal, or a circuit or chip (such as a modem chip, also known as a baseband chip, or a system-on-chip (SoC) chip containing a modem core, or a system-in-package (SIP) chip) responsible for communication functions within the terminal. In this application, a terminal is used as an example for description.

[0045] The communication method includes: receiving first information from a first DU, the first information indicating a first TA to be used when the terminal hands over to a first cell, the first cell belonging to a second DU; starting a first TAT corresponding to the first TA value; when the first TAT is the TAT corresponding to the PTAG to which the first cell belongs, resetting the MAC layer without stopping the operation of the first TAT during the handover to the first cell; or, when the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG, resetting the MAC layer and stopping the operation of the first TAT during the handover to the first cell.

[0046] In this communication method, when the first TAT corresponds to the TAT of the PTAG to which the first cell belongs, the first TAT will continue to run during the handover process to the first cell, thus ensuring that the terminal continues to know the effective remaining time of the first TA based on the first TAT. However, when the first TAT is a different TAT generated by the first DU or the second DU than the TAT corresponding to the PTAG, the terminal can stop the operation of the first TAT and determine the effective remaining time of the first TA by starting the TAT corresponding to the PTAG.

[0047] For example, when the terminal sends a second uplink message to the second DU, or when it successfully establishes a connection with the second DU, or when it stops the first TAT or resets the MAC layer, it starts the TAT corresponding to the PTAG to determine the effective remaining time of the first TA through the TAT corresponding to the PTAG.

[0048] In conjunction with the fourth aspect, in one possible implementation, the first TAT is generated by either the first DU or the second DU. If the first TAT is generated by the second DU, the second DU can indicate the first TAT to the first DU via both the second CU and the first CU.

[0049] In conjunction with the fourth aspect, in one possible implementation, the above method further includes: sending a second message, the second message being used to indicate the remaining time of the first TAT.

[0050] Fifthly, this application provides a communication device capable of implementing any of the first to fourth aspects and any possible implementation thereof. The device includes corresponding modules for performing the described methods. These modules can be implemented in software and / or hardware.

[0051] In a sixth aspect, this application provides a communication device including a processor that can be used to execute a computer program in a memory to implement the methods described in the first to fourth aspects and any possible implementations of the first to fourth aspects.

[0052] Optionally, the device further includes a communication interface, to which the processor is coupled. The communication interface is used to receive signals from other communication devices outside the device and transmit them to the processor, or to send signals from the processor to other communication devices outside the device. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, pin, or other type of communication interface.

[0053] Optionally, the device further includes a memory, to which the processor is coupled. The memory stores program instructions and data. The memory is coupled to the processor, which, when executing the instructions stored in the memory, can implement the methods described in the preceding aspects.

[0054] In a seventh aspect, this application provides a communication device, including a processor and a communication interface. The communication interface is used to receive signals from other communication devices besides the communication device and transmit them to the processor, or to send signals from the processor to other communication devices besides the communication device. The processor implements the methods described in the first to fourth aspects and any possible implementations of the first to fourth aspects through logic circuits or executing code instructions. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, pin, or other type of communication interface.

[0055] Optionally, the apparatus further includes a memory for storing instructions and data. The memory may be coupled to the processor, which, when executing the instructions stored in the memory, implements the methods described in the first to fourth aspects and any possible implementation thereof.

[0056] Eighthly, this application provides a communication device including a processor and a memory, the memory being used to store instructions and data, wherein when the processor executes the instructions stored in the memory, it can implement the methods described in the first to fourth aspects and any possible implementation of the first to fourth aspects.

[0057] Optionally, the device further includes a communication interface for communicating with other communication devices. For example, the communication interface may be a transceiver, circuit, bus, module, pin, or other type of communication interface.

[0058] Ninthly, this application provides a computer-readable storage medium storing a computer program or instructions that, when executed, implement the methods described in the first to fourth aspects and any possible implementations of the first to fourth aspects.

[0059] In a tenth aspect, this application provides a chip system including at least one processor for supporting the implementation of the functions involved in the first to fourth aspects and any possible implementation of the first to fourth aspects, such as receiving or processing data involved in the above methods.

[0060] In one possible design, the chip system also includes a memory for storing program instructions and data, which may be located within or outside the processor.

[0061] The chip system can consist of chips or include chips and other discrete components.

[0062] In one aspect, this application provides a computer program product including instructions that, when executed, implement the methods described in the first to fourth aspects and any possible implementations of the first to fourth aspects. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of a communication system to which embodiments of this application are applicable;

[0064] Figure 2 This is a schematic diagram of a communication system based on a split architecture to which embodiments of this application apply;

[0065] Figure 3 A schematic diagram illustrating the process of a terminal performing cell handover based on LTM;

[0066] Figure 4 A schematic diagram illustrating the process of uplink synchronization between the terminal and the target cell;

[0067] Figure 5 This is a diagram showing the remaining time for TAT;

[0068] Figures 6 to 13 A flowchart illustrating the communication method provided in this application;

[0069] Figure 14 This is a structural schematic diagram of a communication device provided in one embodiment of this application;

[0070] Figure 15 This is a structural schematic diagram of a communication device provided for another embodiment of this application. Detailed Implementation

[0071] The technical solution provided in this application can be applied to various communication systems. For example, applicable communication systems include, but are not limited to: Long Term Evolution (LTE) systems, LTE Frequency Division Duplex (FDD) systems, LTE Time Division Duplex (TDD) systems, sidelink (SL) communication systems, 5th generation (5G) mobile communication systems or new radioaccess technology (NR), non-terrestrial networks (NTN) communication systems, and future communication systems. Future communication systems include, for example, 6th generation (6G) mobile communication systems.

[0072] refer to Figure 1 , Figure 1 This is a schematic diagram of a communication system 1000 to which this application's embodiments apply. It is understood that the system architecture described in this application's embodiments is for the purpose of more clearly illustrating the technical solutions of this application's embodiments and does not constitute a limitation on the technical solutions provided in this application's embodiments. Figure 1 As shown, the communication system 1000 includes a radio access network (RAN) 100, wherein the RAN 100 includes at least one RAN node (e.g., Figure 1 110a and 110b, collectively referred to as 110, may also include at least one terminal (such as...). Figure 1 RAN100, denoted as RAN100, comprises RAN nodes 120a-120j, collectively referred to as RAN120. RAN100 may also include other RAN nodes, such as wireless relay equipment and / or wireless backhaul equipment. Figure 1 (Not shown in the image). Terminal 120 is wirelessly connected to RAN node 110. Terminals and RAN nodes can be interconnected via wired or wireless means. Communication system 1000 may also include core network 200. RAN node 110 is connected to core network 200 via wireless or wired means. The core network equipment in core network 200 and RAN node 110 in RAN 100 can be independent physical devices, or they can be the same physical device integrating the logical functions of core network equipment and RAN node. Communication system 1000 may also include Internet 300.

[0073] RAN100 can be an evolved universal terrestrial radio access (E-UTRA) system, a new radio (NR) system, or a future radio access system as defined in the 3rd generation partnership project (3GPP). RAN100 can also include two or more of the above-mentioned different radio access systems. RAN100 can also be an open RAN (O-RAN).

[0074] RAN nodes, also known as radio access network devices, RAN entities, or access nodes, are used to help terminals access communication systems wirelessly. In one application scenario, an RAN node can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB) in a 5G mobile communication system, or a base station in a future mobile communication system. RAN nodes can also be macro base stations (such as...). Figure 1 110a in the text), can also be a micro base station or an indoor station (such as... Figure 1 110b in the middle can also be a relay node or a donor node.

[0075] In another application scenario, multiple RAN nodes can collaborate to help terminals achieve wireless access, with different RAN nodes implementing different functions of the base station. For example, a RAN node can be a central unit (CU), a distributed unit (DU), or a radio unit (RU). Here, the CU performs the functions of the base station's Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP), and can also perform the functions of the Service Data Adaptation Protocol (SDAP). The DU performs the functions of the base station's Radio Link Control (RANC) and Medium Access Control (MAC) layers, and can also perform some or all of the physical layer functions. For specific descriptions of these protocol layers, refer to the relevant 3GPP technical specifications. The RU can be used to implement radio frequency signal transmission and reception. The CU and DU can be two independent RAN nodes or integrated into the same RAN node, such as within a baseband unit (BBU). The RU can be included in radio frequency equipment, such as in a remote radio unit (RRU) or an active antenna unit (AAU). The CU can be further divided into two types of RAN nodes: CU-control plane and CU-user plane.

[0076] In different systems, RAN nodes may have different names. For example, in an O-RAN system, a CU can be called an open CU (O-CU), a DU can be called an open DU (O-DU), and an RU can be called an open RU (O-RU). The RAN nodes in the embodiments of this application can be implemented through software modules, hardware modules, or a combination of software and hardware modules. For example, a RAN node can be a server loaded with the corresponding software modules. The embodiments of this application do not limit the specific technology or device form used in the RAN nodes. For ease of description, a base station is used as an example of a RAN node in the following description.

[0077] A terminal is a device with wireless transceiver capabilities, capable of sending signals to or receiving signals from a base station. Terminals can also be called terminal equipment, user equipment (UE), mobile station, mobile terminal, etc. Terminals can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables, smart transportation, smart cities, etc. Terminals can be mobile phones, tablets, computers with wireless transceiver capabilities, wearable devices, vehicles, airplanes, ships, robots, robotic arms, smart home devices, etc. The embodiments of this application do not limit the specific technology or device form used in the terminal.

[0078] RAN nodes and terminals can be fixed or mobile. RAN nodes and terminals can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; and they can be deployed on aircraft, balloons, and satellites. The embodiments of this application do not limit the application scenarios of RAN nodes and terminals.

[0079] The roles of RAN nodes and terminals can be relative. For example, Figure 1The helicopter or drone 120i can be configured as a mobile base station. For terminals 120j accessing the wireless access network 100 via 120i, terminal 120i is a base station; however, for base station 110a, 120i is a terminal, meaning that 110a and 120i communicate via a wireless air interface protocol. Of course, 110a and 120i can also communicate via a base station-to-base station interface protocol; in this case, 120i is also a base station relative to 110a. Therefore, both base stations and terminals can be collectively referred to as communication devices. Figure 1 The 110a and 110b in the text can be referred to as communication devices with base station functions. Figure 1 The 120a-120j in the text can be referred to as communication devices with terminal functions.

[0080] Communication between RAN nodes and terminals, between RAN nodes, and between terminals can be conducted using licensed spectrum, unlicensed spectrum, or both simultaneously. Communication can be conducted using spectrum below 6 GHz, spectrum above 6 GHz, or both simultaneously. The embodiments of this application do not limit the spectrum resources used for wireless communication.

[0081] refer to Figure 2 , Figure 2 This is a schematic diagram of a communication system based on a split architecture to which embodiments of this application apply. For example... Figure 2 As shown, access network devices communicate with core network (CN) devices via a backhaul link and with terminals via an air interface. Specifically, the BBU in the access network device communicates with the core network device via the backhaul link; the RU in the access network device communicates with the terminal via an air interface. The BBU communicates with at least one RU via a fronthaul link (FH). The BBU and RU may be co-located or not. A BU may include at least one CU and at least one DU, and the CU and DU can communicate with each other via a midhaul link.

[0082] In a CU-DU separated architecture, the CU possesses some core network functions and can include CU-CP and CU-UP. The CU and DU can be configured according to the protocol layer functions of the wireless network they implement. For example, the CU is configured to implement the functions of the Packet Data Convergence Protocol (PDCP) layer and above (e.g., Radio Resource Control (RRC) layer and / or Service Data Adaptation Protocol (SDAP) layer). The DU is configured to implement the functions of protocol layers below the PDCP layer (e.g., Radio Link Control (RLC) layer, Media Access Control (MAC) layer, and / or Physical Layer). The CU (Control Panel) is configured to implement the functions of protocol layers above the PDCP layer (such as the RRC layer and / or SDAP layer), while the DU (User Panel) is configured to implement the functions of protocol layers at and below the PDCP layer (such as the RLC layer, MAC layer, and / or PHY layer). The CU can control one or more DUs. The CU and DU are connected via an F1 interface. When the CU includes CU-CP and CU-UP, CU-CP is used to implement the control plane functions of the CU, and CU-UP is used to implement the user plane functions of the CU. For example, when the CU is configured to implement the functions of the PDCP layer, RRC layer, and SDAP layer, CU-CP is used to implement the RRC layer functions and the PDCP layer control plane functions, while CU-UP is used to implement the SDAP layer functions and the PDCP layer user plane functions.

[0083] CU, DU, and RU can be deployed in different physical devices. For example, if CU and DU are deployed in the same physical device, then CU and DU can be considered as a single functional entity; or if DU and RU are deployed in the same physical device, then DU and RU can be considered as a single functional entity.

[0084] The above, combined with Figure 1 and Figure 2 This section describes the communication system to which the embodiments of this application are applicable. Below, some terms used in the embodiments of this application are explained. It should be understood that this section is for ease of understanding only and should not be considered as a specific limitation of this application.

[0085] 1. Timing advance (TA)

[0086] In mobile communication, the uplink data latency of a terminal to a base station varies depending on its distance from the base station. For example, for a terminal 1 kilometer away from the base station, the signal propagation delay is approximately 3.33 microseconds (round-trip time is 6.67 microseconds), meaning the terminal's uplink data arrives at the base station 3.33 microseconds after transmission. If this propagation delay is not compensated, the terminal's uplink signal may not arrive at the base station within the allocated time slot, leading to signal interference. For instance, if the base station allocates time slot 1 for terminal 1 to send uplink data and time slot 2 (adjacent to time slot 1) for terminal 2 to send uplink data, without compensation for terminal 1's signal propagation delay, the uplink data sent by terminal 1 may arrive at the base station in time slot 2, affecting the uplink data of terminal 2.

[0087] The Transmission Timing (TA) is primarily used to adjust the uplink transmission time to compensate for the delay in wireless signal propagation, thereby ensuring that the terminal's uplink signal arrives at the base station within the time allocated by the base station. Specifically, TA is the amount of time that the terminal should advance when sending uplink data; TA is typically the signal propagation delay between the base station and the terminal.

[0088] The base station can determine the Terminal's Transmission Time (TA) based on the arrival time of the terminal's uplink transmission and instruct the terminal to send the TA via a Time Advance Command (TAC), a Medium Access Control (MAC) control element (CE), or a Random Access Response (RAR). For ease of understanding, let's take the example of the base station allocating uplink data transmission from terminal 1 to the base station in time slot 1 and from terminal 2 to the base station in time slot 2. To ensure that terminal 1's uplink data arrives at the base station within time slot 1, the terminal should send the uplink signal at the beginning of time slot 1, ahead of the TA (signal propagation delay between terminal 1 and the base station). This ensures that the uplink signal from terminal 1 arrives at the base station within time slot 1 after propagation.

[0089] 2. Timing Advance Group (TAG)

[0090] When multiple cells provide service to a terminal, if two of these cells identify terminals with the same TA (Translation Address), then these two cells are considered to belong to the same TAG (Tag). In this case, the base station indicates the TA corresponding to that TAG to the terminal, allowing the terminal to obtain the TA of terminals identified by cells belonging to that TAG. Alternatively, a TAG can be considered to include a group of cells, where terminals belonging to this group of cells share the same TA.

[0091] Tags can be divided into primary timing advance groups (PTAGs) and secondary timing advance groups (STAGs). A PTAG typically includes the primary cell (Pcell), while a STAG typically includes the secondary cell (Scell). For example, cells providing service to terminals include cell 1, cell 2, cell 3, and cell 4. Cell 1 is a Pcell, and cells 2, 3, and 4 are Scells. If the terminal's timing advance (TA) is the same for cells 1 and 2, and the terminal's TA is the same for cells 3 and 4, then cells 1 and 2 belong to the same tag, and cells 2 and 3 belong to the same tag. Understandably, the tags belonging to cells 1 and 2 are the primary tags, and the tags belonging to cells 3 and 4 are the secondary tags.

[0092] 3. Time alignment timer (TAT)

[0093] The role of TAT can be considered as managing (or maintaining) the synchronization status of uplink data transmission between the terminal and the base station.

[0094] After receiving a TA (Telematics Acquisition), the terminal will either activate or reset the TAT (Time Access Control). Resetting the TAT means that if the terminal has already activated the TAT, when it receives a new TAC (Telematics Acquisition Control) from the base station, the terminal restarts the TAT countdown. For example, if the TAT is a 5-second timer, after receiving TA1 from the base station, the terminal activates the TAT and starts counting down from the 5th second. When the TAT reaches the 3rd second, the terminal receives a new TA2. At this point, the terminal will reset the TAT to 5 seconds and restart the countdown from the 5th second.

[0095] After the terminal starts or resets the TAT, during the TAT's operation (without timeout), the terminal considers the current TA valid and maintains uplink synchronization. If the TAT times out, the terminal considers itself out of uplink synchronization, stops sending uplink data to the base station, and triggers a random access procedure to resynchronize uplink. In other words, based on the TAT, the terminal can determine how long the current TA has been valid and how much validity time remains.

[0096] Mobility management changes the serving cell of a terminal, ensuring uninterrupted service regardless of where the terminal moves within network coverage. Handover is a mobility management function for connected terminals, where the terminal can change its serving cell from one cell to another by performing a cell handover.

[0097] Typically, the cell before the handover is called the source cell, and the cell after the handover is called the target cell. The DU (Distribution Unit) to which the source cell belongs is also called the source DU, and the DU to which the target cell belongs is also called the target DU. The CU (Cellular Unit) to which the source DU belongs is also called the source CU, and the CU to which the target DU belongs is also called the target DU. Understandably, the source CU and the target CU can be the same CU or different CUs. That is, the CUs to which the source DU and the target DU belong can be the same CU or different CUs.

[0098] Layer 1 or Layer 2 triggered mobility (LTM) is a technology used to implement cell handover. L1 refers to the PHY layer; L2 refers to the MAC / RLC / PDCP / SDAP layer. During LTM handover, L2 primarily refers to the MAC layer. Below, we will take the example of the target DU of the target cell after handover and the source DU of the source cell before handover belonging to the same CU managed by them, combined with... Figure 3 This diagram illustrates the process of a terminal performing cell handover based on LTM technology.

[0099] like Figure 3 As shown, the LTM handover process mainly includes LTM preparation, early synchronization, LTM cell handover execution, and LTM cell handover completion. Specifically, the LTM handover process includes steps 1 to 8:

[0100] Step 1: The terminal sends a Layer 3 (L3) measurement report to the CU.

[0101] Step 2: The CU decides to initiate the LTM configuration process based on the L3 measurement report, prepares candidate cell configuration, and sends an RRC reconfiguration message to the terminal, which includes the candidate cell configuration.

[0102] Step 3: The terminal sends an RRC reconfiguration complete message to the CU.

[0103] Before receiving the cell switch command, the terminal may execute steps 4a and 4b.

[0104] Step 4a: The terminal and the candidate cell complete downlink synchronization in advance.

[0105] Step 4b: The terminal and the candidate cell complete uplink synchronization in advance.

[0106] Step 5: The terminal performs L1 measurement on the configured candidate cell and sends an L1 measurement report to the source DU.

[0107] Step 6: After receiving the L1 measurement report, the source DU decides that the terminal should perform an LTM handover to the target cell based on the LTM handover decision. The source DU sends a cell switch command to the terminal through MAC CE signaling. The cell switch command is used to instruct the terminal to handover to the target cell.

[0108] Step 7: The terminal executes a random access procedure to access the target cell.

[0109] In one implementation, if the terminal performs downlink synchronization and line synchronization with the target cell before receiving the cell handover command, the terminal can access the target cell using a random access (RA) method.

[0110] The following explains the process of pre-synchronizing the terminal and the target cell during LTM handover. For example... Figure 4 As shown, the process of the terminal completing uplink synchronization with the target cell includes steps 4.1 to 4.4:

[0111] Step 4.1: The source DU sends a physical downlink control channel (PDCCH) order to the terminal. The PDCCH order is used to instruct the terminal to send the RA preamble to the target cell. The RA preamble can also be called RA preamble, RA preamble sequence, or RA preamble, etc.

[0112] Step 4.2: The terminal sends the RA preamble to the target cell based on the PDCCH order instruction.

[0113] Step 4.3: The target DU determines the terminal's TA (e.g., called the target TA) based on the RA preamble sent by the terminal and forwards it to the source DU through the CU.

[0114] Step 4.4: After receiving the target TA of the terminal forwarded by the CU, the source DU indicates the target TA corresponding to the target cell to the terminal, for example, the target TA is carried in the MAC CE signaling.

[0115] Correspondingly, after receiving the target TA, the terminal will initiate TAT (Time Access Activation) to start timing and determine how long the target TA has been valid and how long it may remain valid. During TAT operation, the terminal considers the target TA valid and can access the target cell using a non-random access method.

[0116] As can be seen, for LTM handover: on the one hand, the information of the candidate cell is sent to the terminal in advance through the source cell, so that the terminal can start synchronizing with the target cell before receiving the cell handover command. This allows the terminal to quickly complete the handover process based on the non-random access method after receiving the cell handover command, thus reducing the handover interruption time.

[0117] With the development of mobile communication technology, CLTM handover was proposed. The difference between CLTM handover and LTM handover lies in the following: In the CLTM handover process, when the terminal determines that the target cell meets the CLTM handover conditions, the terminal performs random access to access the target cell. That is, in the CLTM handover process, the source DU does not need to send a cell handover command to the terminal to indicate the target cell to be handed over to; instead, the terminal determines the target cell to be handed over to itself based on the CLTM handover conditions. For example, CLTM handover conditions include, but are not limited to, the following:

[0118] 1) CondEventA3: The signal quality of the candidate cell is higher than that of the serving cell.

[0119] 2) CondEventA5: The quality of the serving cell is below threshold 1, and the quality of the candidate cell is above threshold 2.

[0120] 3) CondEventLTM3: The candidate cell's beam is higher than the serving cell's beam.

[0121] 4) CondEventLTM5: The quality of the serving cell's beam is below the absolute threshold 1, and the quality of the candidate cell's beam is above the absolute threshold 2.

[0122] However, when a terminal performs cell handover based on CLTM, there is a possibility that after the terminal accesses the target cell, the target DU (Distributed Utility Unit) cannot know the remaining time of the target TAT (Target Time Acquisition) corresponding to the target TA (Target Target Access Transaction). Therefore, it cannot know how much time the target TA has remaining valid, which prevents the target DU from issuing a new TAT in a timely manner. This can lead to uplink out-of-synchronization issues, affecting the terminal's uplink data transmission. For example, ... Figure 5As shown, after receiving the target TA (Target Transaction Acquisition) from the source DU (Dedicated DU) via TAC (Target Access Control) at time 1, the terminal initiates TAT ​​(Target Access Control). Assuming the TAT has a timing duration of 500ms and is based on a countdown timer, if the terminal switches to the target cell at 420ms of TAT execution, the remaining duration of the TAT is 420ms, indicating that the target TA will expire after 420ms. However, since the target DU cannot know the remaining time of the target TAT, it cannot know that the target TA will expire after 420ms, thus failing to send a new TAC to the terminal within the remaining 420ms. This can lead to uplink synchronization issues, affecting the terminal's uplink data transmission.

[0123] In view of this, this application provides a communication method and a communication device. In the communication method provided by this application, the remaining time of the first TAT corresponding to the target TA is reported by the terminal, or the remaining time of the first TAT corresponding to the target TA is reported by the source DU, so that the target DU can know the remaining time of the first TAT when the terminal communicates with the target cell, thereby enabling the target DU to maintain uplink synchronization between the terminal and the target based on the remaining time of the first TAT.

[0124] The communication method provided in the embodiments of this application will be described below with reference to the accompanying drawings. The method provided in this application can be applied to... Figure 1 and Figure 2 The communication system shown is not limited to this embodiment.

[0125] refer to Figure 6 , Figure 6 This is a flowchart illustrating a communication method 600 for reporting the remaining time of a first TAT via a terminal, as provided in one embodiment of this application. The various steps in method 600 are described in detail below.

[0126] S601, the first DU sends first information to the terminal. The first information is used to indicate the first TA used by the terminal when switching to the first cell. The first cell belongs to the second DU. Correspondingly, after receiving the first information, the terminal starts the first TAT corresponding to the first TA.

[0127] In this application, the first DU refers to the DU to which the terminal belongs before performing CLTM handover. The cell to which the terminal accesses before performing CLTM handover is also referred to as the second cell. The second cell belonging to the first DU can also be interpreted in any of the following ways: the second cell is a cell supported / managed / controlled by the first DU. It should be noted that the aforementioned second cell is merely an example of the name of the cell to which the terminal accesses before performing CLTM handover, and it does not constitute a limitation of this application. For example, the second cell can also be described as the source cell, the CLTM handover source cell, etc.

[0128] In this application, the second DU refers to the DU to which the terminal belongs after performing a CLTM handover. The phrase "the first cell belongs to the second DU" can also be interpreted as: the first cell is a cell supported / managed / controlled by the second DU. It should be noted that the aforementioned first cell is merely an example of the name of the cell accessed by the terminal after performing a CLTM handover, and does not constitute a limitation of this application. For example, the first cell can also be replaced with "target cell," "CLTM handover target cell," etc.

[0129] In this application, the CU to which the first DU belongs is referred to as the first CU, and the CU to which the second DU belongs is referred to as the second CU. The second CU can also be called the source CU, and the first CU can also be called the target CU. That is, the first CU is the CU that manages / controls the first DU, and the second CU is the CU that manages / controls the second DU. Therefore:

[0130] In one example, the first CU and the second CU are the same CU, which can be interpreted as any of the following: the first DU and the second DU both belong to the first CU, the first DU and the second DU both belong to the second CU, the first DU and the second DU belong to the same CU, the first DU and the second DU are managed by the same first CU, or the first DU and the second DU are managed by the same second CU.

[0131] In another example, the second CU and the first CU are different. This can be interpreted in any of the following ways: the first CU and the second CU belong to different CUs; ​​or the first CU and the second CU are managed / controlled by different CUs. Optionally, in this scenario, the first CU and the second CU correspond to different communication systems, for example, the first CU corresponds to a 5G system, and the second CU corresponds to an LTE system.

[0132] In this application, the base station consisting of the first DU and the first CU is considered as the source base station, and the base station consisting of the second DU and the second CU is considered as the target base station.

[0133] In this application, prior to S601, the first CU can configure configuration information for at least one candidate cell for the terminal, including the aforementioned first cell. Correspondingly, the terminal can pre-completion downlink and uplink synchronization with each candidate cell based on the configuration information of this at least one candidate cell. Understandably, when the terminal determines that it needs to hand over to one of the candidate cells based on the CLTM handover conditions, it hands over to the selected cell. Understandably, the cell to which the terminal hands over can be understood as the first cell in this application, and the DU to which the terminal belongs can be understood as the second DU in this application. For example, the terminal's current serving cell (which can be understood as the second cell) belongs to DU0, and the candidate cells configured by the first CU for the terminal include cells managed by DU1, DU2, DU3, and / or DU4. When the terminal hands over from the second cell to a cell managed by DU1 (which can be understood as the first cell), DU0 can be understood as the first DU in this application, and DU1 can be understood as the second DU in this application.

[0134] In this application, the terminal can complete downlink and uplink synchronization with the first cell in advance when connecting to the first DU. How the terminal completes downlink synchronization with the first cell can be found in related technical descriptions and will not be repeated here. One implementation method for the terminal to complete uplink synchronization with the first cell in advance includes: the terminal sending an RA preamble to the first cell; after receiving the RA preamble sent by the terminal, the second DU determines the first TA used by the terminal when sending uplink data to the first cell and instructs the first DU to use the first TA through the second CU and the first CU. Understandably, if the first CU and the second CU are the same CU, the second DU forwards the first TA to the first DU through the first CU / second CU. If the first CU and the second CU are different CUs, the second DU first sends the first TA to the second CU, then the second CU forwards it to the first CU, and finally forwards it to the first DU through the first CU. For example, when the first CU and the second CU are the same CU, the second DU calculates the first TA and sends it to the CU through a DU-CU TA INFORMATION TRANSFER message. The CU then forwards the first TA to the source DU via the CU-DUTA INFORMATION TRANSFER message. The CU and DU send / receive (interact) messages through the F1 interface.

[0135] In this application, after the first DU receives the first TA (Transmission Targeting) forwarded by the first CU (Center for Continuous Access Control) used by the terminal to send uplink data to the first cell, the first DU sends first information to the terminal. The first information is used to indicate the first TA used by the terminal when handing over to the first cell. For example, the first information is carried in the MAC CE (Continuous Access Control) signaling.

[0136] In one implementation, the first information includes information indicating a first TAG, where the first TAG is the TAG to which the first cell belongs. Correspondingly, after receiving the first information, the terminal can determine that the first TAG corresponds to the first TAG, thus knowing the first TAG of the first cell. For example, the information indicating the first TAG is the identifier of the first TAG. Understandably, in this implementation, the first TAT corresponding to the first TAG can also be considered the TAT corresponding to the first TAG. The second CU can indicate the first TAG to which the first cell belongs to the first DU, so that the first DU knows the TAG to which the first cell belongs.

[0137] In this application, after receiving the first information, the terminal will activate (or enable) the first TAT corresponding to the first TA to start timing. The first TAT can be implemented in two different ways: 1) and 2).

[0138] Implementation Method 1): After receiving the first information, the terminal initiates the first TAT, which is the TAT corresponding to the PTAG of the first cell after the terminal switches to the first cell. Specifically, the second DU can forward the TAT corresponding to the PTAG of the first cell to the first DU through the second CU and the first CU, so that the first DU knows the TAT corresponding to the PTAG of the first cell. The first DU can configure the TAT corresponding to the PTAG of the first cell to the terminal through RRC signaling, so that the terminal knows the TAT corresponding to the PTAG of the first cell.

[0139] In other words, under implementation method 1), after receiving the first TA, the terminal starts the TAT corresponding to the PTAG of the first cell for timing. For example, if the RRC signaling received by the terminal indicates that the TAT corresponding to the PTAG of the first cell is a TAT with a duration of 500ms, then the terminal starts this 500ms TAT ​​for timing after receiving the first TA.

[0140] Implementation Method 2): After receiving the first TA, the terminal initiates a first TAT that is different from the TAT corresponding to the PTAG of the first cell, generated by either the first DU or the second DU. That is, the first TAT is different from the TAT corresponding to the PTAG of the first cell, and the first TAT can be generated by either the first DU or the second DU. When the first TAT is generated by the second DU, the second DU can indicate the first TAT generated by the second DU to the first DU through the second CU and the first CU, thereby enabling the first DU to learn the first TAT and further instruct it to the terminal.

[0141] Here, the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG to which the first cell belongs. It can also be described as: the first TAT is a TAT generated by the first DU or the second DU that is independent of the TAT corresponding to the PTAG to which the first cell belongs. For example, the first TAT is a TAT with a timing duration of 200ms, and the TAT corresponding to the PTAG to which the first cell belongs is a TAT with a timing duration of 500ms.

[0142] In other words, under implementation method 2), for the same first TA, it can be considered that there are two TATs: one is the first TAT, and the other is the TAT corresponding to the PTAG of the first cell. Based on this implementation method 2), it is possible to flexibly configure the first TAT of different durations for the terminal according to different scenarios. For example, if the terminal is currently in a high-speed scenario (such as a high-speed rail scenario), the TAT corresponding to the PTAG of the first cell may not be suitable for the current handover scenario. In this case, a first TAT with a shorter duration can be configured for the terminal.

[0143] S602, the terminal sends a first cell handover notification to the first DU. The first cell handover notification is used to indicate that the terminal is about to hand over to the first cell. The first cell handover notification includes second information, which is used to indicate the remaining time of the first TAT.

[0144] In other words, in method 600, when the terminal determines that it needs to hand over to the first cell based on the CLTM handover conditions, the terminal will send a first cell handover notification to the first DU to indicate that the terminal is about to hand over to the first cell.

[0145] The first cell handover notification includes second information, which indicates the remaining time of the first TAT. For example, the first cell handover notification includes one or more of the following: the cell identifier of the first cell, the identifier of the uplink or downlink beam of the first cell, so that the first DU is aware of the first cell that the terminal is about to hand over to.

[0146] When the remaining time of the first TAT is indicated by the second information, in one implementation, a correspondence between the remaining time and the gear position can be preset. Then, the second information includes the gear position information corresponding to the remaining time of the first TAT. Correspondingly, the second DU determines the remaining time of the first TAT corresponding to the reported gear position information based on the correspondence. The second information may also include information for indicating the first TAG.

[0147] S603, after receiving the first cell handover notification, the first DU sends the second information to the second DU through the first CU and the second CU.

[0148] Specifically, the first DU sending the second information to the second DU through the first CU and the second CU means that the first DU first sends the second information to the first CU, then the first CU forwards the second information to the second CU, and then the second CU forwards the second information to the second DU.

[0149] Understandably, when the first CU and the second CU are the same CU, the first DU instructs the second information to the second DU through the first CU and the second CU. That is, the first DU instructs the second information to the second DU through the first CU / second CU. For example, the first DU sends the second information to the first CU / second CU through DU-CU CELL SWITCH NOTIFICATION, and the first CU / second CU forwards the second information to the second DU through CU-DU CELL SWITCH NOTIFICATION.

[0150] As can be seen, in method 600, when the terminal determines that it needs to switch to the first cell, it will carry second information in the first cell handover notification sent to the first DU to indicate the remaining time of the first TAT, so as to indicate the remaining time of the first TAT to the second DU through the first DU.

[0151] Understandably, once the second DU learns of the remaining time of the first TAT, the second DU can determine how long the first TAT has been running based on the remaining time of the first TAT, thereby determining how long the first TA has been valid, and further determining how long the validity period of the first TA is left after the terminal accesses the first cell (also known as the remaining valid time of the first TA). This allows the second DU to send a new TAC to the terminal before the first TA expires, so as to ensure uplink synchronization between the terminal and the second DU.

[0152] For example, if the first TAT initiated by the terminal after receiving the first TA is the TAT corresponding to the PTAG of the first cell after the terminal switches to the first cell, then when the second DU receives the remaining time of the first TAT, the remaining time of the first TAT is also the remaining valid time of the first TA.

[0153] For example, if the first TAT is independent of the TAT corresponding to the PTAG of the first cell, then when the second DU receives the remaining time of the first TAT, the second DU can first determine the time the first TAT has been running based on its duration and remaining time, and then determine the remaining valid time of the first TA based on the duration of the TAT corresponding to the PTAG of the first cell and the duration the first TAT has been running. In this scenario, if the first TAT is generated by the first DU, then the first DU can indicate the first TAT generated by the first DU to the second DU through the first CU and the second CU, thereby enabling the second DU to know the duration of the first TAT. For example, if the timing duration of the first TAT is 200 milliseconds, and the timing duration of the TAT corresponding to the PTAG of the first cell is 500 milliseconds, then if the remaining time of the first TAT indicated to the second DU is 100 milliseconds, then the second DU determines that the valid remaining time of the first TA after the terminal accesses the first cell is 400 milliseconds. This applies when the first TAT is independent of the TAT corresponding to the PTAG of the first cell.

[0154] To better understand the technical solution provided by method 600, we will take the example of the first DU and the second DU belonging to the same communication CU (i.e., the first CU and the second CU are the same CU), and combine it with... Figure 7 The technical solution provided by method 600 will be further explained. For example... Figure 7 As shown, the communication methods include:

[0155] Step 1: After the CU and the terminal complete LTM preparation and the terminal and the first cell complete downlink synchronization in advance, the first DU sends a command to the terminal in the PDCCH to indicate the RA preamble to be used when the terminal performs uplink synchronization with the first cell.

[0156] Step 2: The terminal sends the RA preamble to the second DU.

[0157] Step 3: The second DU calculates the first TA with the terminal and sends it to the CU via a DU-CU TAINFORMATION TRANSFER message. The CU then forwards the first TA to the first DU via a CU-DU TAINFORMATION TRANSFER message.

[0158] The CU and the first DU or the second DU can exchange messages through the F1 interface.

[0159] Step 4: After the first DU receives the first TA, it sends first information to the terminal. The first information includes the ID of the first cell and the first TA calculated by the second DU. After receiving the first information, the terminal initiates the first TAT.

[0160] For example, the first information is carried in the MAC CE signaling.

[0161] For example, the first TAT can be the TAT corresponding to the first cell or the TAT corresponding to the first TAG. The meaning of the first TAG is described in Method 600 and will not be repeated here.

[0162] Step 5: Before the CLTM handover, the terminal sends a first cell handover notification to the first DU. The first cell handover notification indicates that the terminal is about to hand over to the first cell.

[0163] The first cell handover notification includes second information, which indicates the remaining time of the first TAT. A more detailed description of the second information can be found in method 600, and will not be repeated here.

[0164] Step 6: The first DU forwards the first cell handover notification message to the CU.

[0165] Step 7: The CU forwards the first cell handover notification to the second DU.

[0166] Step 8: The terminal successfully connected to the second DU.

[0167] Understandable, for Figure 6 In the provided method 600, if the first DU fails to receive the first cell handover notification from the terminal, it may be unable to indicate the remaining time of the first TAT to the second DU. To solve this problem, in one implementation, after the terminal sends the first cell handover notification to the first DU indicating that the terminal is about to hand over to the first cell, if the terminal does not receive an acknowledgment message from the first DU indicating successful reception of the first cell handover notification, the terminal can retransmit the first cell handover notification, thereby ensuring that the first DU can indicate the remaining time of the first TAT to the second DU. In this application, the message indicating that the first DU has successfully received the first cell handover notification is also called the first acknowledgment message. For example, the first acknowledgment message is an acknowledgment (ACK), indicating that the first DU has successfully received the first cell handover notification.

[0168] refer to Figure 8 , Figure 8 This is a flowchart illustrating a communication method 800 for reporting the remaining time of a first TAT via a terminal, as provided in another embodiment of this application. The various steps in method 800 are described in detail below.

[0169] S801, the first DU sends first information to the terminal, the first information being used to indicate the first TA used by the terminal when handing over to the first cell, the first cell belonging to the second DU; correspondingly, the terminal receives the first information and starts the first TAT corresponding to the first TA to start timing.

[0170] A detailed description of this step can be found in [reference]. Figure 6 The description in S601 of method 600 shown will not be repeated here.

[0171] S802, after the terminal accesses the first cell, it sends a first uplink message to the first cell. The first uplink message includes second information, which is used to indicate the remaining time of the first TAT.

[0172] The terminal sending its first uplink message to the first cell after accessing it can also be described as the terminal sending its first uplink message to the second DU after accessing the first cell. Specifically, the terminal determines that it needs to hand over to the first cell based on the CLTM handover conditions and executes the CLTM handover procedure to access the second DU.

[0173] As can be seen, in method 800, after the terminal accesses the second DU, it indicates the remaining time of the maintained first TAT to the second DU. Understandably, once the second DU knows the remaining time of the first TAT, it can determine how long the first TAT has been running (and thus how long the first TA has been valid) based on the remaining time, and further determine how much validity time of the first TA remains after the terminal accesses the first cell (also called the remaining valid time of the first TA). This allows the second DU to send a new TAC to the terminal before the first TA expires, ensuring uplink synchronization between the terminal and the second DU. For details on how to determine the remaining valid time of the first TA, please refer to [reference needed]. Figure 6 The descriptions in the embodiments will not be repeated here.

[0174] To better understand the technical solution provided by method 800, we will take the case where the first DU and the second DU belong to the same communication CU (i.e., the first CU and the second CU are the same CU) as an example, combined with... Figure 9 The technical solution provided by method 800 will be further explained. For example... Figure 9 As shown, the communication methods include:

[0175] Step 1: After the CU and the terminal complete LTM preparation and the terminal and the first cell complete downlink synchronization in advance, the first DU sends a command to the terminal in the PDCCH to indicate the RA preamble to be used when the terminal performs uplink synchronization with the first cell.

[0176] Step 2: The terminal sends the RA preamble to the second DU.

[0177] Step 3: The second DU calculates the first TA with the terminal and sends it to the CU via a DU-CU TAINFORMATION TRANSFER message. The CU then forwards the first TA to the first DU via a CU-DU TAINFORMATION TRANSFER message.

[0178] Step 4: After the first DU receives the first TA, it sends first information to the terminal. The first information includes the ID of the first cell and the first TA calculated by the second DU. After receiving the first information, the terminal initiates the first TAT.

[0179] For a detailed description of this section, please refer to [link / reference]. Figure 7 The description of step 4 in the embodiment will not be repeated here. The meaning of the first TAG is described in method 600, and will not be repeated here.

[0180] Step 5: The terminal determines to hand over to the first cell based on the CLTM handover conditions and executes a random access procedure to access the first cell.

[0181] That is, the terminal determines the identifier of the first cell to which it needs to be handed over, the identifier of the uplink and / or downlink beam of the first cell, based on the CLTM handover condition consultation, and accesses the first cell (that is, accesses the second DU).

[0182] Step 6: The terminal sends a first uplink message to the second DU, which carries the remaining time for indicating the first TAT.

[0183] The above, combined with Figures 6-9This paper introduces two methods for a terminal to report the remaining time of the first Time Advancement Command (TA). Optionally, in method 600 and / or method 800, the first CU can also send an RRC message to the terminal. Correspondingly, the terminal receives the RRC message from the first CU, where the RRC message is used to indicate a first threshold value or a second threshold value. When the RRC message is used to indicate the first threshold value, the terminal can compare the time the first TA has been running with the first threshold value. If the time the first TA has been running is greater than or equal to the first threshold value, the terminal can consider that the first TA is about to expire, and at this time, the terminal can send third information to the first DU. Alternatively, when the RRC message is used to indicate the second threshold value, the terminal can compare the remaining time of the first TA with the second threshold value. If the remaining time of the first TA is less than the second threshold value, the terminal can consider that the first TA is about to expire, and at this time, the terminal can send third information to the first DU. The third information is used to request the first DU to indicate the RA preamble used when performing uplink synchronization with the first cell or for the first DU to send a new Time Advance Command (TAC), thereby enabling the terminal to obtain a new TAC and restart the first TA.

[0184] Optionally, when the timing duration of the first TAT is determined by the second DU, the second DU can indicate the absolute time for generating the first TAT to the first DU through the first CU and the second CU. For example, the absolute time for generating the first TAT can be Coordinated Universal Time (UTC). Understandably, when the second CU and the first CU are the same CU, the second DU instructs the first DU to generate the absolute time for the first TAT through the first CU and the second CU. Alternatively, it can be described as the second DU instructing the first DU to generate the absolute time for the first TAT through the first CU / second CU. Furthermore, the first information sent by the first DU to the terminal can also instruct the second DU to generate the absolute time of the first TAT. Thus, when the terminal receives the first information, it can determine how long the first TAT has been valid based on the absolute time of the second DU generating the first TAT and the time of the currently received first TAT. Then, when starting the first TAT timing, it starts timing from time 1, where the interval between time 1 and the initial time of the first TAT is the time the first TAT has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved. For example, if the interval between the time the terminal receives the first TA and the time the second DU generates the first TA is 50 milliseconds, and the first TAT is a TAT with a timing duration of 200 milliseconds and is based on a countdown method, then after the terminal receives the first information, the terminal will activate the first TAT and start timing from 150 milliseconds. Or,

[0185] When the timing duration of the first TAT is determined by the second DU, the second DU can indicate to the first DU, through the first CU and the second CU, the time during which the first TA has been valid when the second DU sends the first TA to the first DU. Understandably, when the second CU and the first CU are the same CU, the second DU instructing the first DU, through the first CU and the second CU, on the time during which the first TA has been valid when the second DU sends the first TA to the first DU can also be described as the second DU instructing the first DU, through the first CU / second CU, on the time during which the first TA has been valid when the second DU sends the first TA to the first DU. Furthermore, the first information sent by the first DU to the terminal can also include the time during which the first TA has been valid. Thus, when the terminal receives the first information, it can determine how long the first TA has been valid, and then start timing the first TAT from time 1, where the interval between time 1 and the initial time of the first TAT is the time during which the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved. For example, when the second DU sends the first TA to the first DU, the first TA has been valid for 50 milliseconds. The first TAT is a TAT with a timing duration of 200 milliseconds and is based on a countdown method. Then, after the terminal receives the first information, the terminal activates the first TAT and starts timing from 150 milliseconds; or,

[0186] When the timing duration of the first TAT is determined by the second DU, the second DU can indicate to the first DU, through the first CU and the second CU, how much time remains in the first TAT when the second DU sends the first TA to the first DU. Understandably, when the second CU and the first CU are the same CU, the second DU instructing the first DU, through the first CU and the second CU, on how much time remains in the first TAT when the second DU sends the first TA to the first DU can also be described as the second DU instructing the first DU, through the first CU / second CU, on how much time remains in the first TAT when the second DU sends the first TA to the first DU. Furthermore, the first information sent by the first DU to the terminal can also indicate how much time remains in the first TAT. Thus, when the terminal receives the first information, it can determine how long the first TA has been valid based on the timing duration of the first TAT and the indicated remaining time of the first TAT, and then start timing from time 1 when starting the first TAT countdown, where the interval between time 1 and the initial time of the first TAT is the time the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved. For example, the first TAT is a TAT with a timing duration of 200 milliseconds and is based on a countdown method. When the second DU sends the first TA, the first TA has been valid for 50 milliseconds. Then the second DU indicates that there are 150 milliseconds left in the first TAT. After the terminal receives the first information, the terminal starts the first TAT and starts timing from 150 milliseconds.

[0187] refer to Figure 10 , Figure 10 This is a flowchart illustrating a communication method 1000 for reporting the remaining time of a first TAT via a first DU, as provided in one embodiment of this application. The various steps in method 1000 are described in detail below.

[0188] S1001, the first DU sends first information to the terminal and starts the first TAT. The first information is used to indicate the first TA used by the terminal when switching to the first cell. The first cell belongs to the second DU. Correspondingly, after receiving the first information, the terminal starts the first TAT corresponding to the first TA.

[0189] The descriptions of the first DU, the second DU, and the first information can be found in Figure S601, and will not be repeated here.

[0190] In method 1000, when the first DU receives the first TA used to instruct the terminal determined by the second DU to use when handing over to the first cell, the first DU will not only instruct the terminal to use the first TA when handing over to the first cell, but the first DU will also activate the first TAT corresponding to the first TA. That is, in method 1000, both the first DU and the terminal will activate the first TAT corresponding to the first TA.

[0191] Among them, the first TAT can be implemented in two different ways: 1) and 2).

[0192] Implementation Method 1): The first TAT initiated by the terminal and the first DU is the TAT corresponding to the PTAG of the first cell after the terminal hands over to the first cell. Specifically, the second DU can forward the TAT corresponding to the PTAG of the first cell to the first DU through the second CU and the first CU, so that the first DU knows the TAT corresponding to the PTAG of the first cell. The first DU can configure the TAT corresponding to the PTAG of the first cell to the terminal through RRC signaling, so that the terminal knows the TAT corresponding to the PTAG of the first cell.

[0193] For example, if the PTAG of the first cell has a timer duration of 500ms, then for the first DU, after receiving the first TA (Transfer Assist) indicating the handover process for the terminal to the first cell determined by the second DU, the 500ms timer will start counting. Similarly, for the terminal, after receiving the first TA indicated by the first DU via the first information, the 500ms timer will also start counting.

[0194] Implementation Method 2: The first TAT initiated by the terminal and the first DU is a TAT generated by either the first DU or the second DU, which is different from the TAT corresponding to the PTAG to which the first cell belongs. That is, the first TAT is different from the TAT corresponding to the PTAG to which the first cell belongs, and the first TAT can be generated by either the first DU or the second DU. When the first TAT is generated by the second DU, the second DU can indicate the first TAT generated by the second DU to the first DU through the second CU and the first CU, thereby enabling the first DU to learn the first TAT and further instruct it to the terminal.

[0195] Here, the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG to which the first cell belongs. It can also be described as: the first TAT is a TAT generated by the first DU or the second DU that is independent of the TAT corresponding to the PTAG to which the first cell belongs. For example, if the first TAT is a TAT with a timing duration of 200ms, and the TAT corresponding to the PTAG to which the first cell belongs is a TAT with a timing duration of 500ms, then for the first DU, after receiving the first TA (Transfer Assist) used to instruct the terminal determined by the second DU to handover to the first cell, it will start the 200ms TAT ​​to begin timing. Similarly, for the terminal, after receiving the first TA indicated by the first DU through the first information, it will also start the 200ms TAT ​​to begin timing.

[0196] In other words, under implementation method 2), for the same first TA, it can be considered that there are two corresponding TATs: one is the first TAT, and the other is the TAT corresponding to the PTAG to which the first cell belongs. The beneficial effects of configuring the first TAT to a different TAT than the TAT corresponding to the PTAG to which the first cell belongs can be found in [reference needed]. Figure 6 The descriptions in the embodiments will not be repeated here.

[0197] S1002, the terminal sends a second cell handover notification to the first DU. The second cell handover notification is used to indicate that the terminal is about to hand over to the first cell.

[0198] In method 1000, when the terminal determines that it needs to hand over to the first cell based on the CLTM handover conditions, the terminal will send a second cell handover notification to the first DU to indicate that the terminal is about to hand over to the first cell, so that the first DU knows that the terminal is about to hand over to the first cell.

[0199] S1003, after receiving the second cell handover notification, the first DU sends second information to the second DU through the first CU and the second CU to indicate the remaining time of the first TAT based on the first TAT that has been started.

[0200] When the remaining time of the first TAT is indicated by the second information, in one implementation, a correspondence between the remaining time and the gear position can be preset. Then, the second information includes the gear position information corresponding to the remaining time of the first TAT. Correspondingly, the second DU determines the remaining time of the first TAT corresponding to the reported gear position information based on the correspondence. The second information may also include information for indicating the first TAG.

[0201] As can be seen, in method 1000, when the terminal determines that it needs to switch to the first cell, it will send a second cell handover notification to the first DU. Correspondingly, after receiving the second cell handover notification, the first DU will send the remaining time of the first TAT started by the first DU to the second DU through the first CU and the second CU.

[0202] Similarly, in method 1000, after the first DU learns the remaining time of the first TAT, the first DU can determine how long the first TAT has been running based on the remaining time of the first TAT, thereby determining how long the first TA has been valid, and further determining how long the validity period of the first TA is left after the terminal accesses the first cell (also known as the remaining valid time of the first TA), so that the second DU can send a new TAC to the terminal before the first TA expires, so as to ensure uplink synchronization between the terminal and the second DU.

[0203] For example, if the first TAT initiated by the first DU is the TAT corresponding to the PTAG of the first cell after the terminal is switched to the first cell, then when the second DU receives the remaining time of the first TAT, the remaining time of the first TAT is also the remaining valid time of the first TA.

[0204] For example, if the first TAT initiated by the first DU is a TAT that is independent of the TAT corresponding to the PTAG to which the first cell belongs, then when the second DU receives the remaining time of the first TAT, the second DU can first determine the time that the first TAT has been running based on the duration of the first TAT and the remaining time of the first TAT, and then determine the remaining valid time of the first TA based on the duration of the TAT corresponding to the PTAG to which the first cell belongs and the duration that the first TAT has been running.

[0205] To better understand the technical solution provided by method 1000, we will now take the example of the first DU and the second DU belonging to the same communication CU (i.e., the first CU and the second CU are the same CU), and combine it with... Figure 11 This further explains the communication method proposed in this application. For example... Figure 11 As shown, the communication methods include:

[0206] Step 1: After the CU and the terminal complete LTM preparation and the terminal and the first cell complete downlink synchronization in advance, the first DU sends a command to the terminal in the PDCCH to indicate the RA preamble to be used when the terminal performs uplink synchronization with the first cell.

[0207] Step 2: The terminal sends the RA preamble to the second DU.

[0208] Step 3: The second DU calculates the first TA with the terminal and sends it to the CU via the DU-CU TA information transmission message. The CU forwards the first TA to the first DU via the CU-DU TA information transmission message.

[0209] Step 4: After the first DU receives the first TA, it initiates the first TAT and the terminal sends the first information, which includes the ID of the first cell and the first TA calculated by the second DU. After receiving the first information, the terminal initiates the first TAT.

[0210] The relevant description of the first information can be found in the previous text, and will not be repeated here.

[0211] Step 5: Before the CLTM handover, the terminal sends a second cell handover notification to the first DU. The second cell handover notification is used to indicate that the terminal is about to hand over to the first cell.

[0212] In one implementation, the second cell handover notification includes one or more of the following: the ID of the terminal's first cell, and the ID of the uplink and / or downlink beam of the first cell.

[0213] Step 6: The first DU determines the remaining time of the first TAT being maintained and sends second information to the CU to indicate the remaining time of the first TAT.

[0214] For example, the first DU carries the second information in the cell handover notification sent by the first DU to the CU.

[0215] Step 7: The CU forwards the second information to the second DU.

[0216] Step 8: The terminal successfully connected to the second DU.

[0217] It can be seen that, compared with method 1000, the common point is that after receiving the cell handover notification from the terminal indicating that the terminal is about to hand over to the first cell, the first DU reports the remaining time of the first TAT to the second DU through the first CU and the second CU. However, Figure 6 Method 600 and shown Figure 10 The difference between method 1000 and the method shown is: Figure 6In method 600, the terminal carries the remaining time of the first TAT in the cell handover notification sent by the terminal to the first DU, thereby causing the first DU to forward the remaining time of the first TAT to the second DU through the first CU and the second CU. Figure 10 In the method 1000 shown, the first DU also maintains the first TAT. The first DU determines the remaining time of the first TAT based on the first TAT it maintains, and then forwards the remaining time indication of the first TAT to the second DU through the first CU and the second CU.

[0218] Similarly, it is understandable that for Figure 10 In the provided method 1000, if the first DU fails to receive the second cell handover notification from the terminal, there is a problem that the first DU cannot be triggered to indicate the remaining time of the first TAT to the second DU. To solve this problem, in method 1000, after the terminal sends the second cell handover notification to the first DU to indicate that the terminal is about to hand over to the first cell, if the terminal does not receive an acknowledgment message from the first DU indicating successful reception of the second cell handover notification, the terminal can retransmit the second cell handover notification, thereby ensuring that the first DU can be triggered to indicate the remaining time of the first TAT to the second DU. In this application, the message used to indicate that the first DU has successfully received the second cell handover notification is also called the second acknowledgment message. For example, the second acknowledgment message is an acknowledgment (ACK), indicating that the first DU has successfully received the second cell handover notification.

[0219] refer to Figure 12 , Figure 12 This is a flowchart illustrating a communication method 1200 provided in one embodiment of this application. The various steps in method 1200 are described in detail below.

[0220] S1201, the first DU sends first information to the terminal and starts the first TAT. The first information is used to indicate the first TA used by the terminal when switching to the first cell. The first cell belongs to the second DU. Correspondingly, after receiving the first information, the terminal starts the first TAT corresponding to the first TA.

[0221] A detailed description of this step can be found in [reference]. Figure 10 The description in S1001 of method 1000 shown will not be repeated here.

[0222] S1202, after the terminal accesses the first cell, the second CU sends fourth information to the first DU through the first CU. The fourth information is used to request the remaining time of the first TAT corresponding to the first TA.

[0223] Specifically, the terminal determines that it needs to switch to the first cell based on the CLTM handover conditions and executes the CLTM handover procedure to access the first DU.

[0224] S1203, after receiving the fourth information, the first DU sends the second information, which indicates the remaining time of the first TAT, to the second DU through the first CU and the second CU, based on the first TAT that has been started.

[0225] For a detailed description of the first DU sending the second message, please refer to [link / reference]. Figure 11 The description in S1130 of the embodiment will not be repeated here.

[0226] As can be seen, in method 1200, the first DU also maintains the first TAT. After the terminal connects to the second DU, the second CU requests the remaining time of the first TAT from the first DU through the first CU. Correspondingly, the first DU instructs the second DU on the remaining time of the first TAT it maintains through the first CU and the second CU.

[0227] To better understand the technical solution provided by method 1200, we will now take the example of the first DU and the second DU belonging to the same communication CU (i.e., the first CU and the second CU are the same CU), and combine it with... Figure 13 This further explains the communication method proposed in this application. For example... Figure 13 As shown, the communication methods include:

[0228] Step 1: After the CU and the terminal complete LTM preparation and the terminal and the first cell complete downlink synchronization in advance, the first DU sends a command to the terminal in the PDCCH to indicate the RA preamble to be used when the terminal performs uplink synchronization with the first cell.

[0229] Step 2: The terminal sends the RA preamble to the second DU.

[0230] Step 3: The second DU calculates the first TA with the terminal and sends it to the CU via the DU-CU TA information transmission message. The CU forwards the first TA to the first DU via the CU-DU TA information transmission message.

[0231] Step 4: After the first DU receives the first TA, it initiates the first TAT and the terminal sends the first information, which includes the ID of the first cell and the first TA calculated by the second DU. After receiving the first information, the terminal initiates the first TAT.

[0232] The relevant description of the first information can be found in the previous text, and will not be repeated here.

[0233] Step 5: The terminal determines to hand over to the first cell based on the CLTM handover conditions and executes a random access procedure to access the first cell.

[0234] Step 6: The second DU sends a connection completion message (access success) to the CU through the F1 interface to indicate that the terminal has successfully accessed the first cell (that is, to indicate that the terminal has successfully accessed the second DU).

[0235] Step 7: The CU sends a fourth message to the second DU, which is used to request the remaining time of the first TAT.

[0236] For example, the CU may carry the fourth information in a CU-DU TAT INFORMATIONREQUEST message. Alternatively, the CU may carry the fourth information in a UE CONTEXTRELEASE COMMAND message. The fourth information may also include the identifier of the first cell and / or the identifier of the first TAG.

[0237] Step 8: The first DU sends second information to the CU to indicate the remaining time of the first TAT.

[0238] For example, the first DU carries the second information in the DU-CU TAT information response. Another example is that the first DU carries the second information in the UE context release command message.

[0239] Step 9: The CU forwards the second information to the second DU.

[0240] The above, combined with Figures 10-13 This paper introduces two methods for the first DU to report the remaining time of the first TAT. Optionally, this applies when the timing duration of the first TAT is determined by the second DU:

[0241] The second DU can indicate the absolute time for generating the first TA to the first DU via the first CU and the second CU. For example, the absolute time for generating the first TA can be Coordinated Universal Time (UTC). Understandably, when the first CU and the second CU are the same CU, the second DU instructs the first DU on the absolute time for generating the first TA via the first CU and the second CU; alternatively, it can be described as the second DU instructing the first DU on the absolute time for generating the first TA via the first CU / second CU. Thus, when the first DU initiates the first TAT, it can determine how long the first TA has been valid based on the absolute time of the first TA generated by the second DU and the time of the currently received first TA. Then, when starting the first TAT, it can begin timing from time 1, where the interval between time 1 and the initial time of the first TAT is the time the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved. Alternatively,

[0242] When the timing duration of the first TAT is determined by the second DU, the second DU can indicate to the first DU, through the first CU and the second CU, the time during which the first TA was valid when the second DU sent the first TA to the first DU. Understandably, when the first CU and the second CU are the same CU, the second DU can indicate to the first DU, through the first CU and the second CU, the time during which the first TA was valid when the second DU sent the first TA to the first DU. Alternatively, it can be described as the second DU indicating to the first DU, through the first CU / second CU, the time during which the first TA was valid when the second DU sent the first TA to the first DU. In this way, the first DU can determine how long the first TA has been valid based on the time of the currently received first TA, and then start timing from time 1 when starting the first TAT, where the interval between time 1 and the initial time of the first TAT is the time during which the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved. Alternatively,

[0243] When the timing duration of the first TAT is determined by the second DU, the second DU can instruct the first DU, through the first CU and the second CU, how much time remains in the first TAT when the second DU sends the first TA to the first DU. Understandably, when the second CU and the first CU are the same CU, the second DU can instruct the first DU, through the first CU and the second CU, how much time remains in the first TAT when the second DU sends the first TA to the first DU. Alternatively, it can be described as the second DU instructing the first DU, through the first CU / second CU, how much time remains in the first TAT when the second DU sends the first TA to the first DU. In this way, the first DU can determine how long the first TA has been valid based on the timing duration of the first TAT and the indicated remaining time of the first TAT, and then start timing from time 1 when starting the first TAT, where the interval between time 1 and the initial time of the first TAT is the time the first TA has been valid. Based on this implementation, the accuracy of the reported remaining time of the first TAT can be improved.

[0244] The above, combined with Figures 6 to 13 This application describes a method for reporting the remaining time of the first TAT via a terminal or the first DU, so that the second DU can know the remaining time of the first TAT when the terminal accesses the first cell.

[0245] In this application, after the terminal initiates the first TAT, during the process of the terminal accessing the first cell:

[0246] If the first TAT is the TAT corresponding to the PTAG of the first cell, then the terminal can reset the MAC layer during the handover to the first cell but not stop the operation of the first TAT, thereby ensuring that the terminal continues to know the effective remaining time of the first TA based on the first TAT.

[0247] If the first TAT is a different TAT generated by the first DU or the second DU than the TAT corresponding to the PTAG, since the first TAT and the TAT corresponding to the PTAG are independent of each other, the terminal can reset the MAC layer and stop the operation of the first TAT during the handover to the first cell, and determine the effective remaining time of the first TA by starting the TAT corresponding to the PTAG. In this implementation, the terminal can also report the remaining time of the first TAT when it stops, for example, by including the remaining time of the first TAT in the first cell handover notification sent to the first DU, or by including the remaining time of the first TAT in the first uplink message sent by the terminal to the first cell. The implementation method of the terminal reporting the remaining time of the first TAT through the first cell handover notification and the first uplink message can be referred to the description above, and will not be repeated here.

[0248] For example, the terminal starts the TAT corresponding to PTAG when: the terminal sends a second uplink message to the second DU, or when a connection is successfully established with the second DU, or when the first TAT is stopped or the MAC layer is reset.

[0249] For example, when the first TAT is a different TAT generated by the first DU or the second DU than the TAT corresponding to the PTAG, the first TAT has a timing duration of 200 milliseconds, while the TAT corresponding to the PTAG has a timing duration of 500 milliseconds. In this case, during the handover to the first cell, the terminal can stop the first TAT, which has already run for 100 milliseconds, and then send a second uplink message to the second DU. Alternatively, upon successfully establishing a connection with the second DU, or upon stopping the first TAT or resetting the MAC layer, the terminal can start the TAT corresponding to the PTAG to begin timing. In this case, the terminal starting the TAT corresponding to the PTAG to begin timing means that the terminal starts timing the TAT corresponding to the PTAG from time 2, where the interval between time 2 and the initial time of the TAT corresponding to the PTAG is the time that the first TA has been valid.

[0250] Figure 14 This is a structural schematic diagram of a communication device provided in an embodiment of this application. Specifically, as shown... Figure 14 As shown, the device 1400 includes: a transceiver module 1401 and a processing module 1402.

[0251] For example, in an embodiment of the first device, device 1400 can be applied to a terminal.

[0252] Specifically, the transceiver module 1401 is used to: receive first information from the first DU, the first information being used to indicate the first TA used when the terminal switches to the first cell, the first cell belonging to the second DU; the processing module 1402 is used to start the first TAT corresponding to the first TA; the transceiver module 1401 is also used to: send second information, the second information being used to indicate the remaining time of the first TAT.

[0253] In one possible implementation, the transceiver module 1401 is further configured to: retransmit the first cell handover notification if no acknowledgment message is received from the first DU; the acknowledgment message is used to indicate that the first DU has successfully received the first cell handover notification.

[0254] In one possible implementation, if the first TAT is the TAT corresponding to the PTAG, the processing module 1402 is further configured to: reset the MAC layer during the handover to the first cell but not stop the operation of the first TAT.

[0255] In one possible implementation, if the first TAT is a different TAT generated by the first DU or the second DU than the TAT corresponding to the PTAG, the processing module 1402 is further configured to: reset the MAC layer and stop the operation of the first TAT during the handover to the first cell.

[0256] In one possible implementation, the processing module 1402 is further configured to: start the TAT corresponding to PTAG when sending a second uplink message to the second DU, or when successfully establishing a connection with the second DU, or when stopping the first TAT or resetting the MAC layer.

[0257] In one possible implementation, the transceiver module 1401 is further configured to: receive an RRC message from a first CU, the RRC message indicating a first threshold value or a second threshold value, the first CU being the CU to which the first DU belongs; and the transceiver module 1401 is further configured to: send third information to the first DU if the time the first TAT has been running is greater than or equal to the first threshold value, or if the remaining time of the first TAT is less than the second threshold value; wherein the third information is used to request the first DU to indicate the RA preamble used when performing uplink synchronization with the first cell, or the third information is used to request the first DU to send a TAC.

[0258] For example, in an embodiment of the second device, device 1400 may be applied to the first DU.

[0259] Specifically, the transceiver module 1401 is used to: send first information to the terminal, the first information being used to indicate the first TA used by the terminal when handing over to the first cell, the first cell belonging to the second DU; and send second information, the second information including the remaining time of the first TAT corresponding to the first TA when the terminal handovers to the first cell.

[0260] In one possible implementation, the transceiver module 1401 is further configured to: receive a first cell handover notification from the terminal and then send second information, wherein the first cell handover notification is used to indicate that the terminal is about to handover to the first cell, and the first cell handover notification carries the second information.

[0261] In one possible implementation, the processing module 1402 is further configured to: initiate the first TAT corresponding to the first TA.

[0262] In one possible implementation, the transceiver module 1401 is further configured to: after receiving a second cell handover notification from the terminal, send the second information based on the initiated first TAT, wherein the second cell handover notification is used to indicate that the terminal is about to handover to the first cell.

[0263] In one possible implementation, the transceiver module 1401 is further configured to: after receiving the fourth information, send the second information based on the started first TAT, wherein the fourth information is used to request the remaining time of the first TAT corresponding to the first TA, and the second CU is the CU to which the second DU belongs.

[0264] For example, in an embodiment of the third device, device 1400 may be applied to the second DU.

[0265] Specifically, the transceiver module 1401 is used to: instruct the first DU to use the first TA when the terminal switches to the first cell, the first cell belonging to the second DU; the transceiver module 1402 is also used to: receive second information, the second information being used to indicate the remaining time of the first device TAT corresponding to the first TA when the terminal switches to the first cell.

[0266] In one possible implementation, the transceiver module 1401 is further configured to: receive a first uplink message from the terminal, wherein the first uplink message carries second information; the first uplink message is an uplink message sent by the terminal to the first cell after the terminal accesses the first cell.

[0267] For a more detailed description of the first information, second information, third information, fourth information, and first TAT, please refer to the description in the method embodiment above, which will not be repeated here.

[0268] Figure 15 This is a structural schematic diagram of another communication device provided in an embodiment of this application. Figure 15 The apparatus shown can be used to perform the method described in any of the foregoing embodiments.

[0269] like Figure 15 As shown, the device 1500 of this embodiment includes a memory 1501 and a processor 1502. In one implementation, the device 1500 further includes a communication interface 1503 and a bus 1504. The memory 1501, processor 1502, and communication interface 1503 are interconnected via the bus 1504.

[0270] The memory 1501 can be a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM). The memory 1501 can store programs, and when the program stored in the memory 1501 is executed by the processor 1502, the processor 1502 performs the execution... Figures 6 to 13 The steps of the method shown.

[0271] The processor 1502 may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, used to execute relevant programs to implement the embodiments of this application. Figures 6 to 13 The method shown.

[0272] The processor 1502 can also be an integrated circuit chip with signal processing capabilities. In the implementation process, the embodiments of this application... Figures 6 to 13 Each step of the method can be accomplished by integrated logic circuitry in the hardware of the processor 1502 or by instructions in software form.

[0273] The processor 1502 described above can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or a conventional processor, etc.

[0274] The steps of the method disclosed in the embodiments of this application can be directly manifested as being executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory 1501. Processor 1502 reads information from memory 1501 and, in conjunction with its hardware, completes the functions required by the units included in the device of this application. For example, it can execute... Figures 6 to 13 The various steps / functions of the illustrated embodiment.

[0275] The communication interface 1503 can use, but is not limited to, transceivers to enable communication between the device 1500 and other devices or communication networks.

[0276] Bus 1504 may include a pathway for transmitting information between various components of device 1500 (e.g., memory 1501, processor 1502, communication interface 1503).

[0277] It should be understood that the device 1500 shown in the embodiments of this application can be deployed in network devices or terminals.

[0278] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be a usable medium accessible to a computer or a data storage device such as a server or data center containing one or more sets of usable media. The usable medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0279] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0280] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0281] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not limit the implementation process of the embodiments of this application.

[0282] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0283] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0284] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0285] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0286] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0287] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory, random access memory, magnetic disks, or optical disks.

Claims

1. A communication method, characterized in that, Applied to terminals, including: Receive first information from the first distributed unit (DU), the first information being used to indicate the first timing advance (TA) used by the terminal when handing over to the first cell, the first cell belonging to the second DU; Start the first time alignment timer TAT corresponding to the first TA; Send a second message, which indicates the remaining time of the first TAT.

2. The method according to claim 1, characterized in that, The second information is carried in the first uplink message; The first uplink message is an uplink message sent by the terminal to the first cell after the terminal accesses the first cell.

3. The method according to claim 1, characterized in that, The second information is carried in the first cell handover notification sent to the first DU; The first cell handover notification is used to indicate that the terminal is about to handover to the first cell.

4. The method according to claim 3, characterized in that, The method further includes: If no acknowledgment message is received from the first DU, the first cell handover notification is retransmitted. The acknowledgment message indicates that the first DU has successfully received the first cell handover notification.

5. The method according to any one of claims 1 to 4, characterized in that, The first TAT is the TAT corresponding to the Primary Time Advance Group (PTAG) of the first cell after the terminal switches to the first cell; or... The first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG.

6. The method according to claim 5, characterized in that, If the first TAT is the TAT corresponding to the PTAG, the method further includes: During the handover to the first cell, the Media Access Control (MAC) layer is reset but the operation of the first TAT is not stopped.

7. The method according to claim 5, characterized in that, If the first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG, the method further includes: During the handover to the first cell, the MAC layer is reset and the operation of the first TAT is stopped.

8. The method according to claim 7, characterized in that, The method further includes: The TAT corresponding to the PTAG is started when the second uplink message is sent to the second DU, or when a connection is successfully established with the second DU, or when the first TAT or MAC layer reset is stopped.

9. The method according to any one of claims 1 to 8, characterized in that, The method further includes: Receive a Radio Resource Control (RRC) message from a first centralized unit (CU), the RRC message being used to indicate a first threshold value or a second threshold value, the first CU being the CU to which the first DU belongs; If the time that the first TAT has been running is greater than or equal to the first threshold, or if the remaining time of the first TAT is less than the second threshold, send the third information to the first DU; The third information is used to request the first DU to indicate the RA preamble used when performing uplink synchronization with the first cell, or the third information is used to request the first DU to send a time advance command (TAC).

10. The method according to any one of claims 1 to 9, characterized in that, The first information includes information for indicating a first TAG, where the first TAG is the TAG to which the first cell belongs; Wherein, the first TAT corresponding to the first TA is the TAT corresponding to the first TAG.

11. The method according to claim 10, characterized in that, The second information includes information for indicating the first TAG.

12. The method according to any one of claims 1 to 11, characterized in that, The communication method is applicable to cell handover of Mobility CLTM based on condition-triggered Layer 1 or Layer 2.

13. A communication method, characterized in that, Applied to the first distributed unit (DU), including: Send first information to the terminal, the first information being used to indicate the first time advance (TA) used by the terminal when handing over to the first cell, the first cell belonging to the second DU; Send a second message, which includes the remaining time of the first time alignment timer TAT corresponding to the first TA when the terminal switches to the first cell.

14. The method according to claim 13, characterized in that, The method further includes: After receiving a first cell handover notification from the terminal, the second information is sent. The first cell handover notification is used to indicate that the terminal is about to hand over to the first cell, and the second information is carried in the first cell handover notification.

15. The method according to claim 13, characterized in that, When sending the first information to the terminal, the method further includes: Start the first TAT corresponding to the first TA.

16. The method according to claim 15, characterized in that, The sending of the second information includes: Upon receiving a second cell handover notification from the terminal, the second information is sent based on the activated first TAT. The second cell handover notification is used to indicate that the terminal is about to hand over to the first cell.

17. The method according to claim 15, characterized in that, The sending of the second information includes: Upon receiving the fourth information, the second information is sent based on the initiated first TAT. The fourth information is used to request the remaining time of the first TAT corresponding to the first TA, and the second CU is the CU to which the second DU belongs.

18. The method according to any one of claims 13 to 17, characterized in that, The first information carries the absolute time when the second DU generates the first TA.

19. The method according to any one of claims 13 to 18, characterized in that, The first information includes information for indicating a first TAG, where the first TAG is the TAG to which the first cell belongs; Wherein, the first TAT corresponding to the first TA is the TAT corresponding to the first TAG.

20. A communication method, characterized in that, Applied to the second distributed unit (DU), including: The first DU is instructed on the first timing advance (TA) used when the terminal switches to the first cell, where the first cell belongs to the second DU. The second information is received, which is used to indicate the remaining time of the first time alignment timer TAT corresponding to the first TA when the terminal switches to the first cell.

21. The method according to claim 20, characterized in that, The receiving of the second information includes: Receive a first uplink message from the terminal, wherein the first uplink message carries the second information; The first uplink message is an uplink message sent by the terminal to the first cell after the terminal accesses the first cell.

22. The method according to claim 20 or 21, characterized in that, The first TAT is the TAT corresponding to the Primary Time Advance Group (PTAG) of the first cell after the terminal switches to the first cell; or... The first TAT is a TAT generated by the first DU or the second DU that is different from the TAT corresponding to the PTAG.

23. A communication device, characterized in that, It includes modules for implementing the method as described in any one of claims 1 to 12; or, it includes modules for implementing the method as described in any one of claims 13 to 19; or, it includes modules for implementing the method as described in any one of claims 20 to 22.

24. A communication device, characterized in that, Includes a processor for causing the communication device to implement the method as described in any one of claims 1 to 12, or the method as described in any one of claims 13 to 19, or the method as described in any one of claims 20 to 22, by executing a computer program or instructions, and / or by logic circuitry.

25. The apparatus according to claim 24, characterized in that, It also includes a memory for storing computer programs or instructions, and / or, configuration files for the logic circuitry.

26. The apparatus according to claim 24 or 25, characterized in that, It also includes a communication interface for inputting and / or outputting signals.

27. A computer-readable storage medium storing a computer program or instructions thereon, characterized in that, When the computer program or instructions are executed, the method of any one of claims 1 to 12 is performed, or the method of any one of claims 13 to 19 is performed, or the method of any one of claims 20 to 22 is performed.

28. A computer program product, characterized in that, The method includes a computer program, and when the computer program or instructions are run, the method of any one of claims 1 to 12 is performed, or the method of any one of claims 13 to 19 is performed, or the method of any one of claims 20 to 22 is performed.

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