Synchronization method and apparatus

Abstract

The present application relates to the technical field of communications, and provides a synchronization method and apparatus. In the method, a terminal can acquire a timing offset between a target cell and a source cell, determine uplink timing of the terminal for the target cell on the basis of the timing offset, and send uplink information to the target cell on the basis of the uplink timing. By means of the described method, the terminal can quickly determine the uplink timing for the target cell, thereby reducing the latency of cell handover.

Description

Synchronization Method and Device

[0001] This application claims priority to Chinese Patent Application No. 202410517999.0, filed with the State Intellectual Property Office of China on April 26, 2024, entitled "Synchronization Method and Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communication technology, and in particular to synchronization methods and apparatus. Background Technology

[0003] In communication systems, to ensure service continuity for terminals, radio access network (RAN) nodes can hand over the terminal to a target cell before the terminal leaves the serving cell, allowing the target cell to continue providing services. For inter-cell handover scenarios, before sending data to the target cell, the terminal also needs to initiate random access to complete uplink synchronization with the target cell. The time spent on uplink synchronization by the terminal is relatively long, resulting in prolonged cell handover latency and impacting user experience. Summary of the Invention

[0004] This application provides a synchronization method and apparatus that can reduce the uplink synchronization latency of a terminal for a target cell, thereby reducing the latency of cell handover.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] Firstly, a synchronization method is provided that can be executed by a terminal. Here, "terminal" can refer to the terminal itself, or to a processor, circuit, module, logic node, chip, or chip system within the terminal that implements the method.

[0007] The method includes: acquiring a first time difference, determining a first uplink timing based on the first time difference, and sending uplink information to a first cell based on the first uplink timing. Wherein, the first time difference is the timing deviation between the first cell and a second cell, the first cell is the target cell for cell handover by the terminal, and the second cell is the source cell for cell handover by the terminal. The first uplink timing is the uplink timing of the terminal for the first cell.

[0008] Based on the method provided in the first aspect above, the terminal can determine its uplink timing for the first cell according to the first time difference, thus allowing the terminal to skip the random access procedure in the first cell. In related technologies, a four-step random access procedure requires the terminal to interact with the first cell four times, and a two-step random access procedure also requires the terminal to interact with the first cell twice. Therefore, the above method can effectively reduce the uplink synchronization latency of the terminal for the first cell, thereby reducing the cell handover latency.

[0009] In one possible implementation, obtaining the first time difference includes receiving information about the first time difference.

[0010] Based on the above possible implementation methods, the terminal can receive information about the first time difference and determine the first time difference accordingly. For example, the terminal can receive information about the first time difference from the RAN node managing the first cell, or from the RAN node managing the second cell.

[0011] In one possible implementation, the information of the first time difference is carried in a system message, a radio resource control message, or a media access control-control element message.

[0012] Based on the above possible implementation methods, the terminal can obtain information about the first time difference through system messages, radio resource control messages, or media access control-control element messages.

[0013] In one possible implementation, obtaining the first time difference includes: receiving first information and second information, the first information indicating the timing of a first cell and the second information indicating the timing of a second cell; and determining the first time difference based on the first information and the second information.

[0014] Based on the above possible implementation methods, the terminal can obtain the timing of the first cell and the timing of the second cell, and determine the first time difference based on the timing of the first cell and the timing of the second cell. For example, the first time difference is equal to the timing of the first cell minus the timing of the second cell.

[0015] In one possible implementation, the method further includes: sending third information, which is used to request at least one of the first information or the second information, wherein the third information is a preamble, or the third information is sent using a wake-up signal.

[0016] Based on the above possible implementation methods, the terminal can send third information to request the first information and / or the second information, thereby determining the first time difference based on the first information and the second information.

[0017] In one possible implementation, the first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

[0018] Based on the above possible implementation methods, the terminal can determine the first uplink timing according to the transmission delay between the terminal and the first cell.

[0019] In one possible implementation, the first uplink timing is also related to a first transmission delay. The first transmission delay is determined based on a first transmission distance, which is the distance between the terminal and the first radio access network node managing the first cell.

[0020] Based on the above possible implementation methods, the terminal can determine the first transmission delay based on the distance between the terminal and the first wireless access network node, and determine the first uplink timing based on the first transmission delay. For example, the first uplink timing is to advance the downlink timing of the terminal for the first cell by (2×td1), where × is a multiplication sign and td1 is the first transmission delay.

[0021] In one possible implementation, the first transmission distance is determined based on a first time difference, a second transmission distance, a first downlink timing, and a second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

[0022] Based on the above possible implementation methods, the terminal can determine the first transmission distance according to the first time difference, the second transmission distance, the first downlink timing, and the second downlink timing, so that the terminal can determine the first uplink timing according to the first transmission distance.

[0023] In one possible implementation, the radio access network node managing the first cell is different from the radio access network node managing the second cell.

[0024] Based on the above possible implementation methods, the terminal can determine the uplink timing for the target cell according to the first time difference in the inter-site handover scenario.

[0025] In one possible implementation, the first time difference can be positive or negative.

[0026] Secondly, a synchronization method is provided, which can be executed by a first radio access network node or a second radio access network node. Here, the first radio access network node can refer to the first radio access network node itself, or to a processor, circuit, module, logic node, chip, or chip system within the first radio access network node that implements the method. Similarly, the second radio access network node can refer to the second radio access network node itself, or to a processor, circuit, module, logic node, chip, or chip system within the second radio access network node that implements the method. For example, the first radio access network node is the target radio access network node for cell handover by the terminal, and the second radio access network node is the source radio access network node for cell handover by the terminal.

[0027] The method includes: sending information about a first time difference to the terminal. The first time difference is the timing deviation between a first cell and a second cell, where the first cell is the target cell for the terminal to perform cell handover, and the second cell is the source cell for the terminal to perform cell handover; the first time difference is used by the terminal to determine a first uplink timing, where the first uplink timing is the uplink timing of the terminal for the first cell.

[0028] Based on the method provided in the second aspect above, information about the first time difference can be sent to the terminal so that the terminal can determine its uplink timing for the first cell based on the first time difference. Therefore, the terminal can skip the random access procedure in the first cell. In related technologies, a four-step random access procedure requires the terminal to interact with the first cell four times, and a two-step random access procedure also requires the terminal to interact with the first cell twice. It is evident that the above method can effectively reduce the uplink synchronization latency of the terminal for the first cell, thereby reducing the cell handover latency.

[0029] In one possible implementation, the first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

[0030] Based on the above possible implementation methods, the terminal can determine the first uplink timing according to the transmission delay between the terminal and the first cell. For example, the first uplink timing is to advance the downlink timing of the terminal for the first cell by (2×td1), where × is a multiplication sign and td1 is the first transmission delay.

[0031] In one possible implementation, the first transmission delay is determined based on a first transmission distance, which is the distance between the terminal and the first radio access network node managing the first cell.

[0032] Based on the above possible implementation methods, the terminal can determine the first transmission delay according to the distance between the terminal and the first wireless access network node managing the first cell, so that the terminal can determine the first uplink timing according to the first transmission delay.

[0033] In one possible implementation, the first transmission distance is determined based on a first time difference, a second transmission distance, a first downlink timing, and a second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

[0034] Based on the above possible implementation methods, the terminal can determine the first transmission distance according to the first time difference, the second transmission distance, the first downlink timing, and the second downlink timing, so that the terminal can determine the first uplink timing according to the first transmission distance.

[0035] In one possible implementation, the method further includes: receiving fourth information from a first access network node, the first access network node being an access network node managing a first cell, the fourth information indicating the timing of the first cell; and determining a first time difference based on the fourth information and the timing of the second cell.

[0036] Based on the above possible implementation methods, the second radio access network node can obtain the timing of the first cell from the first radio access network node, determine the first time difference based on the timing of the first cell and the timing of the second cell, so as to send the information of the first time difference to the terminal.

[0037] In one possible implementation, the radio access network node managing the first cell is different from the radio access network node managing the second cell.

[0038] Based on the above possible implementation methods, the terminal can determine the uplink timing for the target cell according to the first time difference in the inter-site handover scenario.

[0039] In one possible implementation, the first time difference can be positive or negative.

[0040] In one possible implementation, the information about the first time difference is carried in a system message, a radio resource control message, or a media access control-control element message.

[0041] Based on the above possible implementation methods, the first or second radio access network node can send the first time difference information to the terminal through system messages, radio resource control messages, or media access control-control element messages.

[0042] In one possible implementation, the method further includes: receiving fifth information from a second access network node, the second access network node being an access network node that manages the second cell, the fifth information indicating the timing of the second cell; and determining a first time difference based on the fifth information and the timing of the first cell.

[0043] Based on the above possible implementation methods, the first radio access network node can obtain the timing of the second cell from the second radio access network node, determine the first time difference based on the timing of the second cell and the timing of the first cell, and send the information of the first time difference to the terminal.

[0044] Thirdly, a communication device is provided for implementing the above-described method. This communication device can be the terminal described in the first aspect. The communication device includes modules, units, or means corresponding to the above-described method, which can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above-described functions.

[0045] In one possible implementation, the communication device may include a processing module and an interface module. The processing module can be used to implement the processing functions in any of the above aspects and their possible implementations. The processing module may be, for example, a processor. The interface module, also called an interface unit, is used to implement the sending and / or receiving functions in any of the above aspects and their possible implementations. The interface module may consist of an interface circuit, a transceiver, a transceiver unit, or a communication interface.

[0046] In one possible implementation, the processing module is used to obtain a first time difference, which is a timing deviation between a first cell and a second cell, where the first cell is the target cell for the terminal to perform cell handover and the second cell is the source cell for the terminal to perform cell handover; the processing module is also used to determine a first uplink timing based on the first time difference, where the first uplink timing is the uplink timing of the terminal for the first cell; the processing module is also used to control the interface module to send uplink information to the first cell according to the first uplink timing.

[0047] In one possible implementation, the processing module is specifically used to control the interface module to receive information about the first time difference.

[0048] In one possible implementation, the information of the first time difference is carried in a system message, a radio resource control message, or a media access control-control element message.

[0049] In one possible implementation, the processing module is specifically configured to receive first information and second information, the first information indicating the timing of the first cell and the second information indicating the timing of the second cell; the processing module is also specifically configured to determine a first time difference based on the first information and the second information.

[0050] In one possible implementation, the interface module is also used to send third information, which is used to request at least one of the first or second information. The third information is a preamble, or the third information is sent using a wake-up signal.

[0051] In one possible implementation, the first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

[0052] In one possible implementation, the first transmission delay is determined based on a first transmission distance, which is the distance between the terminal and the first radio access network node managing the first cell.

[0053] In one possible implementation, the first transmission distance is determined based on a first time difference, a second transmission distance, a first downlink timing, and a second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

[0054] In one possible implementation, the radio access network node managing the first cell is different from the radio access network node managing the second cell.

[0055] In one possible implementation, the first time difference can be positive or negative.

[0056] Fourthly, a communication device is provided for implementing the above-described method. This communication device can be the first or second radio access network node described in the second aspect. The communication device includes modules, units, or means corresponding to the above-described method, which can be implemented in hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above-described functions.

[0057] In one possible implementation, the communication device may include a processing module and an interface module. The processing module can be used to implement the processing functions in any of the above aspects and their possible implementations. The processing module may be, for example, a processor. The interface module, also called an interface unit, is used to implement the sending and / or receiving functions in any of the above aspects and their possible implementations. The interface module may consist of an interface circuit, a transceiver, a transceiver unit, or a communication interface.

[0058] In one possible implementation, the interface module is used to send information about a first time difference to the terminal. The first time difference is the timing deviation between the first cell and the second cell. The first cell is the target cell for the terminal to perform cell handover, and the second cell is the source cell for the terminal to perform cell handover. The first time difference is used by the terminal to determine the first uplink timing, which is the uplink timing of the terminal for the first cell.

[0059] In one possible implementation, the first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

[0060] In one possible implementation, the first transmission delay is determined based on a first transmission distance, which is the distance between the terminal and the first radio access network node managing the first cell.

[0061] In one possible implementation, the first transmission distance is determined based on a first time difference, a second transmission distance, a first downlink timing, and a second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

[0062] In one possible implementation, the interface module is further configured to receive fourth information from a first access network node, which is an access network node that manages the first cell, and the fourth information indicates the timing of the first cell; the processing module is configured to determine a first time difference based on the fourth information and the timing of the second cell.

[0063] In one possible implementation, the radio access network node managing the first cell is different from the radio access network node managing the second cell.

[0064] In one possible implementation, the first time difference can be positive or negative.

[0065] In one possible implementation, the information of the first time difference is carried in a system message, a radio resource control message, or a media access control-control element message. In another possible implementation, the interface module is further configured to receive fifth information from a second access network node, which is an access network node managing the second cell, and the fifth information indicates the timing of the second cell; the processing module is further configured to determine the first time difference based on the fifth information and the timing of the first cell.

[0066] Fifthly, a communication device is provided, comprising: a processor; configured to cause the communication device to perform the method described in any of the preceding aspects by executing a computer program (or computer-executable instructions) stored in a memory, and / or by means of logic circuitry. The communication device may be a terminal as described in the first aspect; or, the communication device may be a first or second wireless access network node as described in the second aspect. Optionally, the number of processors may be one or more.

[0067] In one possible implementation, the communication device also includes a memory.

[0068] In one possible implementation, the processor and memory are integrated together; alternatively, the memory is independent of the processor.

[0069] In one possible implementation, the communication device further includes a communication interface for communicating with other devices, such as transmitting or receiving data and / or signals. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

[0070] In one possible implementation, the communication device is a chip or a chip system. Optionally, when the communication device is a chip system, it can be composed of chips or may include chips and other discrete components.

[0071] A sixth aspect provides a communication device, comprising: a processor and an interface circuit; the interface circuit being configured to receive a computer program or instructions and transmit them to the processor; the processor being configured to execute the computer program or instructions to cause the communication device to perform the method described in any of the preceding aspects. The communication device may be a terminal as described in the first aspect; or, the communication device may be a first wireless access network node or a second wireless access network node as described in the second aspect. Optionally, the number of processors may be one or more.

[0072] In one possible implementation, the communication device is a chip or a chip system. Optionally, when the communication device is a chip system, it can be composed of chips or may include chips and other discrete components.

[0073] In a seventh aspect, a computer-readable storage medium is provided, which stores instructions that, when executed on a computer, cause the computer to perform the methods described in any of the preceding aspects.

[0074] Eighthly, a computer program product containing instructions is provided, which, when run on a computer, enables the computer to perform the methods described in any of the preceding aspects.

[0075] A ninth aspect provides a communication system comprising a terminal for performing the method described in the first aspect, and a first or second wireless access network node for performing the method described in the second aspect.

[0076] In one possible implementation, the communication system further includes a first network device for performing the method described in the first aspect above.

[0077] The technical effects of any possible implementation of aspects three through nine can be found in the technical effects of any one of aspects one through two or different possible implementations of any one of aspects, and will not be repeated here.

[0078] Understandably, provided that the solutions do not contradict each other, the solutions in the above aspects can be combined. Attached Figure Description

[0079] Figure 1 is a schematic diagram of the communication system architecture provided in this application;

[0080] Figure 2 is a schematic diagram of the hardware structure of the communication device provided in this application;

[0081] Figure 3 is a flowchart illustrating the synchronization method provided in this application.

[0082] Figure 4 is a schematic diagram of the timing deviation between the first clock and the second clock provided in this application;

[0083] Figure 5A is a schematic diagram of the first uplink timing and the first downlink timing provided in this application;

[0084] Figure 5B is a schematic diagram of the first downlink timing and the second downlink timing provided in this application;

[0085] Figure 5C is a schematic diagram of the first uplink timing and the second uplink timing provided in this application;

[0086] Figure 6 is a flowchart of the synchronization method provided in this application (II).

[0087] Figure 7 is a schematic diagram of the medium access control-control element (MAC-CE) message format provided in this application;

[0088] Figure 8 is a flowchart illustrating the synchronization method provided in this application.

[0089] Figure 9 is a schematic diagram of the communication device provided in this application. Detailed Implementation

[0090] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0091] The method provided in this application can be used in various communication systems. For example, the communication system can be a Universal Mobile Telecommunications System (UMTS) system, a Long Term Evolution (LTE) system, a 5th generation (5G) communication system, a Wireless Fidelity (WiFi) system, a 3rd Generation Partnership Project (3GPP) related communication system, a communication system evolving after 5G (such as a 6th generation (6G) communication system), or a system integrating multiple systems, etc., without limitation. Among them, 5G can also be referred to as New Radio (NR). The method provided in this application is described below using the communication system 1000 shown in Figure 1 as an example. Figure 1 is only a schematic diagram and does not constitute a limitation on the applicable scenarios of the technical solution provided in this application.

[0092] Figure 1 shows a schematic diagram of the architecture of the communication system 1000 provided in this application. In Figure 1, the communication system 1000 includes a RAN 100. Optionally, the communication system 1000 also includes a core network (CN) 200 and an Internet 300. The RAN 100 includes at least one RAN node (as shown in Figure 1, 110a and 110b, collectively referred to as 110) and at least one terminal (as shown in Figure 1, 120a-120j, collectively referred to as 120). The RAN 100 may also include other RAN nodes, such as wireless relay devices and / or wireless backhaul devices (not shown in Figure 1). The terminal 120 is wirelessly connected to the RAN node 110. The RAN node 110 is wirelessly or wiredly connected to the core network 200. The core network equipment in the core network 200 and the RAN node 110 in the RAN 100 can be different physical devices, or they can be the same physical device integrating core network logical functions and wireless access network logical functions.

[0093] RAN 100 can be a 3GPP-related cellular system, such as a 4G or 5G mobile communication system, or a future-oriented evolution system (such as a 6G mobile communication system). RAN 100 can also be an open access network (open RAN, O-RAN, or ORAN), a cloud radio access network (CRAN), or a WiFi system. RAN 100 can also be a communication system that integrates two or more of the above systems.

[0094] RAN node 110, sometimes also referred to as access network equipment, RAN entity, or access node, constitutes part of the communication system and is used to help terminals achieve wireless access. Multiple RAN nodes 110 in the communication system 1000 can be of the same type or different types.

[0095] In one possible scenario, a RAN node can be a base station, an evolved NodeB (eNodeB), an access point (AP), a transmission reception point (TRP), a next-generation NodeB (gNB), a next-generation base station in a 6G mobile communication system, a base station in a future mobile communication system, or an access node in a WiFi system. A RAN node can be a macro base station (as shown in Figure 1, 110a), a micro base station or indoor station (as shown in Figure 1, 110b), a relay node or donor node, or a radio controller in a CRAN scenario. Optionally, a RAN node can also be a server, wearable device, vehicle, or in-vehicle equipment. For example, the access network equipment in vehicle-to-everything (V2X) technology can be a roadside unit (RSU). In some scenarios, the roles of RAN node 110 and terminal 120 are relative. For example, a helicopter or drone, typically configured as a terminal, can also be configured as a mobile base station, and devices accessing the RAN via the helicopter or drone are configured as terminals.

[0096] In another possible scenario, multiple RAN nodes collaborate to assist the terminal in achieving wireless access, with different RAN nodes each implementing some of the base station's functions. Specifically, RAN nodes can be central units (CUs), distributed units (DUs), or radio units (RUs), etc. For example, a CU can perform the functions of the base station's radio resource control (RRC) layer and packet data convergence protocol (PDCP) layer. A CU can also perform the functions of the service data adaptation protocol (SDAP) layer. A DU can perform the functions of the base station's radio link control (RLC) layer and medium access control (MAC) layer. A DU can also perform some or all of the physical layer functions. An RU can be used to implement radio frequency signal transmission and reception. CUs and DUs can be set up separately or included in the same network element, such as a baseband unit (BBU). The RU can be included in radio frequency equipment or radio frequency units, such as in a remote radio unit (RRU), an active antenna unit (AAU), or a remote radio head (RRH). Furthermore, the CU can be further divided into the CU-control plane (CP) and the CU-user plane (UP).

[0097] In different systems, CU (or CU-CP and CU-UP), DU, or RU may have different names, but those skilled in the art will understand their meaning. For example, in an ORAN system, CU can also be called O-CU (open CU), DU can also be called O-DU, CU-CP can also be called O-CU-CP, CU-UP can also be called O-CU-UP, and RU can also be called O-RU. For ease of description, this application uses CU, CU-CP, CU-UP, DU, and RU as examples. Any of the units among CU (or CU-CP, CU-UP), DU, and RU in this application can be implemented through software modules, hardware modules, or a combination of software and hardware modules.

[0098] In another possible scenario, the RAN node is a network device within a superstation architecture. For example, the RAN node could be a superstation or a capacity station. The frequency of the superstation can be lower than or equal to that of the capacity station. Cells managed by the superstation can be called anchor cells or coverage cells, while cells managed by the capacity station can be called capacity cells. Typically, anchor cells operate at low frequencies, have wide coverage, and can communicate with terminals using frequency division duplex (FDD). The frequency synchronization accuracy requirement for FDD between stations is ±0.05ppm, and there is no time synchronization requirement between FDD stations. Capacity cells operate at higher frequencies, and their coverage is less than that of anchor cells. Capacity cells can communicate with terminals using time division duplex (TDD). The frequency synchronization accuracy requirement for TDD between stations is ±0.05ppm, and the time synchronization requirement for TDD between stations is ±1.5µs. In a communication system, capacity layer cells can be flexibly turned on or off based on their load and service type. Consequently, terminals can switch between capacity layer cells and basic layer cells to ensure service continuity.

[0099] The terminal in this application, such as terminal 120, is a device with wireless transceiver capabilities. The terminal can be deployed on land, including indoors, outdoors, handheld, or vehicle-mounted; it can also be deployed on water (such as on ships); and it can be deployed in the air (such as on airplanes, balloons, and satellites). The terminal can also be referred to as a terminal device, which can be user equipment (UE), mobile station (MS), mobile terminal (MT), or a device used to provide voice or data connectivity to users. The UE includes handheld devices with wireless communication capabilities, vehicle-mounted devices (e.g., cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed trains, etc.), wearable devices (e.g., smartwatches, smart bracelets, pedometers, etc.), or computing devices. Exemplarily, the UE can be a mobile phone, tablet computer, laptop computer, PDA, mobile internet device (MID), satellite terminal, or computer with wireless transceiver capabilities. UE can also be a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless modem, a point-of-sale (POS) machine, customer-premises equipment (CPE), a smart robot, a robotic arm, workshop equipment, smart home devices (e.g., refrigerators, televisions, air conditioners, electricity meters, etc.), a wireless terminal in industrial control, a wireless terminal in autonomous driving, a wireless terminal in telemedicine, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in intelligent transportation, a wireless terminal in a smart city, a wireless terminal in a smart home, an in-vehicle terminal, a roadside unit (RSU) with terminal functionality, or a flying device (e.g., a smart robot, a hot air balloon, a drone, an airplane), etc. A terminal can also be other devices with terminal functionality; for example, a terminal can be a device that acts as a terminal in device-to-device (D2D) communication.

[0100] By way of example and not limitation, in this application, the terminal can be a wearable device. Wearable devices, also known as wearable smart devices, are a general term for devices that utilize wearable technology to intelligently design and develop everyday wearables, such as glasses, gloves, watches, clothing, and shoes. Wearable devices are portable devices that are worn directly on the body or integrated into a user's clothing or accessories. For example, wearable devices are not merely hardware devices, but also devices that achieve powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include devices that are feature-rich, large in size, and can achieve complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as devices that focus on only one type of application function and need to be used in conjunction with other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0101] In this application, the terminal can be a terminal in an Internet of Things (IoT) system. IoT is an important component of future information technology development, and its main technical feature is connecting objects to networks through communication technologies, thereby realizing an intelligent network of human-machine interconnection and machine-to-machine interconnection. The terminal in this application can be a terminal in machine-type communication (MTC).

[0102] The terminal in this application can be an on-board module, on-board component, on-board chip, on-board unit (OBU), or telematics box (T-BOX) built into a vehicle as one or more components or units. The vehicle can implement the methods of this application through the built-in on-board module, on-board component, on-board chip, on-board unit, or T-BOX. The terminal can also be a complete vehicle device. Therefore, this application can be applied to vehicle networking, such as vehicle-to-everything (V2X), long-term evolution vehicle (LTE-V), and vehicle-to-vehicle (V2V).

[0103] In one possible scenario, the terminal connects to a single RAN node, and both the RAN node to which the terminal connects and the core network to which the RAN node connects use the same network standard. For example, in Figure 1, terminal 120i is connected to RAN node 110a, and RAN node 110a is connected to core network 200. Here, RAN node 110a is a 5G base station, and core network 200 is a 5G core; alternatively, RAN node 110a can be a 6G base station, and core network 200 can be a 6G core.

[0104] In another possible scenario, the terminal connects to multiple RAN nodes, which can be of the same or different standards. Taking dual connectivity (DC) between terminal 120f and RAN nodes 110b and 110a as an example, RAN node 110b is a 5G base station, RAN node 110a is a 6G base station, and core network 200 is a 5G core. RAN node 110b can act as the primary station, and RAN node 110a as the secondary station. Alternatively, RAN node 110b and RAN node 110a can both be 5G and 6G base stations, and core network 200 is a 6G core. RAN node 110a can act as the primary station, and RAN node 110b as the secondary station. Or, both RAN nodes 110b and 110a can be 6G base stations, and core network 200 is a 6G core. One of RAN nodes 110b and 110a can act as the primary station, and the other as the secondary station.

[0105] In this application, based on the connection status between the terminal and the RAN node and core network, the communication system can support three terminal states: idle, connected, and inactive. The idle state can also be called the radio resource control idle (RRC-idle) state or RRC idle state; the connected state can also be called the radio resource control connected (RRC-connected) state or RRC connected state; and the inactive state can also be called the radio resource control inactive (RRC-inactive) state or RRC inactive state. A terminal in the RRC connected state has established an RRC connection with the RAN node. A terminal in the RRC idle state has not established an RRC connection with the RAN node. A terminal in the RRC inactive state suspends data processing, but the RAN node still maintains the terminal's context information. In short, the air interface state of a terminal in the RRC inactive state is similar to that of a terminal in the RRC idle state, but from the core network's perspective, the terminal in the RRC inactive state is still in the RRC connected state.

[0106] In this application, the mobility management of the terminal differs depending on its state. For example, a terminal in RRC connected state can perform cell handover. A terminal in RRC idle state can perform cell reselection or tracking area update. A terminal in RRC inactive state can perform cell reselection, RAN notification area (RNA) update, or tracking area update. Cell handover can take various forms, including layer 3 (L3) based cell handover, condition handover (CHO), or L1 / L2 triggered mobility (LTM) based cell handover.

[0107] In L3-based cell handover, the source RAN node can configure measurement objects (such as the synchronization signal block (SSB) or channel state information reference signal (CSI-RS) of a candidate cell) for the terminal via RRC Reconfiguration messages. The terminal can perform measurements on the measurement objects, obtain the measurement results of the candidate cell (such as L3 measurement results), and send the measurement results to the source RAN node via a measurement report. After receiving the measurement report, the source RAN node can determine whether there is a new serving cell suitable for the terminal. If so, the source RAN node can instruct the terminal to perform cell handover.

[0108] In the aforementioned process, if the radio environment between the terminal and the source RAN node deteriorates, the measurement report sent by the terminal may fail to reach the source RAN node, or the handover command sent by the source RAN node after receiving the measurement report may fail to reach the terminal, ultimately leading to handover failure. In this case, the terminal will recognize the radio link failure and initiate an RRC reconstruction process, impacting user experience. Therefore, to reduce the probability of handover failure and improve handover reliability, 3GPP R16 introduced conditional handover. Conditional handover allows the source RAN node to send a handover command to the terminal in advance, before the radio environment between the terminal and the source RAN node deteriorates. This handover command can carry the radio parameter configuration of the candidate target RAN node and the triggering conditions for handover execution. Therefore, after receiving the handover command, the terminal knows how to access the candidate target RAN node. When the terminal finds a RAN node among the candidate target RAN nodes that meets the handover triggering conditions, the terminal can autonomously decide to initiate handover execution, thus increasing the chance of successful message transmission and significantly improving the handover success rate.

[0109] In L3-based cell handover, both the measurement configuration information for configuring the measurement object and the measurement reports reported by the terminal are carried in RRC signaling. In conditional handover, the measurement configuration information for configuring the measurement object is also carried in RRC signaling. Since the effective time of RRC signaling is at least tens of milliseconds, this introduces a corresponding latency, resulting in a relatively large handover delay and a longer period of interrupted data transmission by the terminal. Furthermore, compared to Layer 1 (L1) or Layer 2 (L2) signaling, RRC signaling has a higher overhead. Therefore, 3GPP R18 introduced LTM-based cell handover. The core idea is that the source RAN node can pre-configure LTM candidate cells for the terminal via RRC signaling, allowing the terminal to perform downlink and uplink synchronization in advance within the LTM candidate cells. The terminal can also report the measurement results of the LTM candidate cells via L1 measurement reports. Subsequently, the source RAN node can use MAC-CE to carry handover commands to instruct the terminal to perform cell handover.

[0110] In communication systems, regardless of the type of cell handover, cell handover can be categorized into intra-site handover scenarios, inter-site Xn handover scenarios, and inter-site NG handover scenarios, depending on whether the serving cells before and after the handover belong to different RAN nodes, or whether there are corresponding Xn interfaces between RAN nodes when they cross sites. In intra-site handover scenarios, the serving cells before and after the handover belong to the same RAN node, so there is no issue of asynchrony between the serving cells. In inter-site handover scenarios (such as inter-site Xn handover or inter-site NG handover), the serving cells before and after the handover belong to different RAN nodes, so asynchrony may occur. To address this, the synchronization method provided in this application can be used to achieve fast uplink synchronization, thereby reducing cell handover latency and improving user experience. This synchronization method will be specifically described in Figures 3, 6, and 8 below.

[0111] It is understood that the communication system 1000 shown in Figure 1 is for illustrative purposes only and is not intended to limit the technical solutions of this application. Those skilled in the art should understand that in specific implementations, the communication system 1000 may also include other devices, and the number of RAN nodes and terminals may be determined according to specific needs without limitation.

[0112] Optionally, each network element or device (such as a RAN node or terminal) in Figure 1 of this application may also be referred to as a communication device, which may be a general-purpose device or a special-purpose device. This application does not make any specific limitation on this.

[0113] Optionally, the functions of each network element or device (e.g., RAN node or terminal) in Figure 1 of this application can be implemented by one device, multiple devices working together, or one or more functional modules within a single device. This application does not impose specific limitations on these functions. It is understood that the aforementioned functions can be network elements in hardware devices, software functions running on dedicated hardware, a combination of hardware and software, or virtualization functions instantiated on a platform (e.g., a cloud platform).

[0114] In practical implementation, each network element or device shown in Figure 1 (e.g., RAN node or terminal) can adopt the composition structure shown in Figure 2, or include the components shown in Figure 2. Figure 2 is a schematic diagram of the hardware structure of a communication device applicable to this application. It is understood that the communication device 20 includes means of necessary forms such as modules, units, elements, circuits, or interfaces, which are appropriately configured together to execute the solution provided in this application. For example, the communication device 20 includes one or more processors 201 for implementing the method provided in this application.

[0115] Processor 201 can be a general-purpose processor or a dedicated processor. For example, processor 201 can be a baseband processor or a central processing unit (CPU). The baseband processor can be used to process communication protocols and communication data, while the CPU can be used to control the communication device 20 (such as a RAN node, terminal, or chip), execute software programs, and process data from the software programs. Optionally, in one design, processor 201 may include program 205 (sometimes also referred to as code or instructions), which can be run on processor 201 to cause the communication device 20 to perform the methods described in the embodiments below. In yet another possible design, communication device 20 includes circuitry (not shown in FIG2) for implementing the functions of the RAN node or terminal in the embodiments below.

[0116] Optionally, the communication device 20 may include one or more memories 203. The memory 203 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM), cache, or other type of dynamic storage device capable of storing information and instructions. It may also be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media, or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory provided in this application may generally be non-volatile. Optionally, the memory 203 stores a program 206 (sometimes referred to as code or instructions), which can be run on the processor 201 to cause the communication device 20 to perform the methods described in the following method embodiments.

[0117] Optionally, data may also be stored in the processor 201 and / or the memory 203. The processor 201 and the memory 203 may be configured separately or integrated together.

[0118] Optionally, the communication device 20 may also include a transceiver 202 and / or an antenna 204. The processor 201, sometimes referred to as a processing unit, controls the communication device 20. The transceiver 202, sometimes referred to as a transceiver unit, transceiver, transceiver circuit, or transceiver, is used to realize the transmission and reception functions of the communication device 20 through the antenna 204.

[0119] It is understood that the composition shown in Figure 2 does not constitute a limitation on the communication device. In addition to the components shown in Figure 2, the communication device may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0120] The method provided in this application will now be described with reference to the accompanying drawings. Each network element in the following embodiments may include the components shown in Figure 2, which will not be elaborated upon further.

[0121] It is understood that the methods described below in this application use RAN nodes and terminals as examples to illustrate the interaction, but this application does not limit the execution entities of the interaction. For example, the RAN node in the methods provided in the embodiments of this application can also be a chip, chip system, or processor that supports the RAN node in implementing the method, or it can be a logical node, logical module, or software that can implement all or part of the RAN node's functions; similarly, the terminal in the methods provided below can also be a chip, chip system, or processor that supports the terminal in implementing the method, or it can be a logical node, logical module, or software that can implement all or part of the terminal's functions.

[0122] Figure 3 shows a synchronization method provided in this application, which may include the following steps:

[0123] S301: The terminal obtains the first time difference.

[0124] In this application, the terminal can be any one of the terminals in the communication system 1000 shown in Figure 1.

[0125] In this application, the first time difference is the timing deviation or absolute timing deviation between the first cell and the second cell. For example, the first time difference is equal to the timing of the first cell minus the timing of the second cell. That is, the first cell and the second cell may have different clock synchronizations. The first cell is the target cell or candidate target cell for cell handover by the terminal, and the second cell is the source cell for cell handover by the terminal. For example, the first cell is synchronized with a first clock, and the second cell is synchronized with a second clock. Synchronization of the first cell with the first clock can be understood as the first cell timing / counting based on the first clock, and synchronization of the second cell with the second clock can be understood as the second cell timing / counting based on the second clock. The first clock and the second clock are different. For example, the first clock is the clock of the RAN node (e.g., the first RAN node) managing the first cell, and the second clock is the clock of the RAN node (e.g., the second RAN node) managing the second cell.

[0126] In this application, there may be a timing deviation or an absolute timing deviation between the first clock and the second clock. For example, for the same time unit, if the first clock is used, the starting time of the time unit is t1; if the second clock is used, the starting time of the time unit is t2. Since t1 and t2 are different, the timing deviation can be positive or negative. Of course, in specific applications, the timing deviation can also be equal to 0, without limitation. It is understood that the time unit in this application is a segment of resources in the time domain. For example, a time unit includes at least one symbol, at least one slot, at least one subframe, or at least one radio frame, etc. It is understood that the unit of the time unit can also be a time unit, such as n milliseconds (ms), n microseconds (µm), or n nanoseconds (nm), etc., where n is a positive number. The starting time of the above-mentioned time unit can also be replaced with the ending time of the time unit.

[0127] For example, taking wireless frame 401 with index 0 as shown in Figure 4, if the start time of wireless frame 401 is T3 and the end time is T4 for the first clock, and the start time of wireless frame 401 is T1 and the end time is T2 for the second clock, then the timing deviation between the first clock and the second clock is equal to the difference between T3 and T1, or equal to the difference between T4 and T2. For example, the timing deviation between the first clock and the second clock is s as shown in Figure 4.

[0128] Understandably, since the first cell is synchronized with the first clock and the second cell is synchronized with the second clock, the timing deviation between the first and second clocks can be understood as the timing deviation between the first and second cells. Therefore, the above description of the timing deviation between the first and second clocks applies to the first time difference. It should also be understood that the timing deviation between the first and second clocks can be understood as the timing deviation between the first RAN node and the second RAN node.

[0129] Understandably, in some scenarios, there is no time synchronization requirement between base layer cells and capacity layer cells in a supercell architecture. Therefore, the first cell can be a base layer cell, and the second cell can be a capacity layer cell; or, the first cell can be a capacity layer cell, and the second cell can be a base layer cell. In other scenarios, there is no time synchronization requirement for cells communicating with the terminal using FDD. Therefore, both the first and second cells can communicate with the terminal using FDD, or the first cell can communicate with the terminal using TDD, and the second cell can communicate with the terminal using FDD.

[0130] In this application, the first RAN node and the second RAN node are different. For example, the first RAN node is the RAN node in the communication system 1000 that is connected to the terminal for communication, such as RAN node 110a, and the second RAN node is the RAN node in the communication system 1000 that the terminal may switch to or will switch to, such as RAN node 110b. It can be seen that the second RAN node can also be called the source RAN node, and the first RAN node can also be called the target RAN node.

[0131] S302: The terminal determines the first uplink timing based on the first time difference.

[0132] In this application, the first uplink timing is the uplink timing of the terminal for the first cell. The first uplink timing can be used by the terminal to determine the time or moment to send an uplink signal to the first RAN node. That is, the first time difference can be used to determine the uplink timing of the terminal for the first cell. It should be understood that the first time difference in this application can also be replaced by a second time difference. The second time difference is the timing deviation between the second cell and the first cell, or the timing deviation between the second clock and the first clock. For example, the second time difference is equal to the timing of the second cell minus the timing of the first cell. This application uses the first time difference as an example to describe the specific process of the terminal determining the uplink timing for the first cell. It is understood that the principle by which the terminal determines the above-mentioned uplink timing based on the second time difference is similar to the principle by which the terminal determines the above-mentioned uplink timing based on the first time difference, and will not be elaborated further.

[0133] In this application, the first uplink timing is also related to the first transmission delay. The first transmission delay is the transmission delay between the terminal and the first cell, or the transmission delay between the terminal and the first RAN node.

[0134] One possible design is that the first uplink timing is determined based on the first transmission delay (hereinafter referred to as td1) and the first downlink timing. The first downlink timing is the downlink timing of the terminal for the first cell, and can be used by the terminal to determine the time or moment to receive the downlink signal from the first RAN node.

[0135] Understandably, there is a distance between the terminal and the first RAN node. Therefore, after the first RAN node sends a downlink signal, the terminal will not receive it immediately, but will receive it after a time td1. Thus, the first downlink timing can be determined based on the timing of the first clock and td1. For example, the first downlink timing is achieved by delaying the timing of the first clock by td1. For example, in Figure 5A, a downlink signal sent by the first RAN node at time T1 can be received by the terminal at time (T1+td1). Furthermore, due to the distance between the first RAN node and the terminal, for an uplink signal sent by the terminal to reach the first RAN node at time T1, the terminal needs to send the uplink signal td1 earlier than time T1. Therefore, the first uplink timing can be determined based on the timing of the first clock and td1. For example, the first uplink timing is achieved by advancing the timing of the first clock by td1. For example, in Figure 5A, an uplink signal sent by the terminal at time T2 can be received by the first RAN node at time T1, where T2+td1=T1.

[0136] Understandably, in practical applications, the terminal may not be able to obtain the timing of the first clock. For example, when the first clock is the clock of the first RAN node, the terminal cannot obtain the timing of the first clock and therefore cannot determine the first uplink timing based on the timing of the first clock. In this case, the terminal can use the first downlink timing as a timing reference to determine the first uplink timing. Specifically, since the first downlink timing delays the timing of the first clock by td1, and the first uplink timing advances the timing of the first clock by td1, if the first downlink timing is used as a timing reference, the first uplink timing advances the first downlink timing by (2×td1). See Figure 5A for details. Here, (2×td1) represents 2 multiplied by td1.

[0137] In summary, once the terminal determines the first transmission delay and the first downlink timing, it can determine the first uplink timing. The following describes how the terminal determines the first transmission delay and the first downlink timing.

[0138] 1. The method by which the terminal determines the first transmission delay

[0139] This application uses the following three methods as examples to illustrate how a terminal determines the first transmission delay.

[0140] Method 1.1: The first RAN node sends (or broadcasts) the absolute time information of the agreed-upon signal to the terminal. This absolute time information indicates the absolute time at which the first RAN node sends the agreed-upon signal. The agreed-upon signal can be a signal defined in the protocol or a pre-agreed signal. For example, the agreed-upon signal could be the first SSB on the radio frame with index 0, the first system information block (SIB) on that radio frame, or SIB 1 in the system information (SI) window. After receiving this absolute time information, the terminal can determine a first transmission delay by combining it with the actual absolute time the terminal receives the agreed-upon signal. For example, the first transmission delay can be equal to the difference between the absolute time the terminal receives the agreed-upon signal and the absolute time the first RAN node sends the agreed-upon signal.

[0141] As an example, the first RAN node determines the absolute time for transmitting the agreed signal as t1 based on a non-terrestrial network clock (such as a Global Navigation Satellite System (GNSS) clock) and sends (or broadcasts) t1 to the terminal. The terminal determines the time for receiving the agreed signal as t2 based on a non-terrestrial network clock (such as a GNSS clock), then the first transmission delay is equal to (t2-t1).

[0142] Method 1.2: The first RAN node sends (or broadcasts) the absolute time information of the agreed-upon time to the terminal. This absolute time information indicates the absolute time of the agreed-upon time. The agreed-upon time can be a time defined in the protocol or a pre-agreed time; for example, the agreed-upon time might be the time corresponding to the start symbol of the first SSB sent by the first RAN node. After receiving this absolute time information, the terminal can determine the first transmission delay by combining it with the absolute time of receiving the first SSB. For example, the first transmission delay is equal to the difference between the absolute time of receiving the first SSB and the absolute time indicated by the first RAN node. It should be understood that the agreed-upon time can also have other designs; for example, the agreed-upon time could be the start time of the radio frame with index 0.

[0143] As an example, the first RAN node determines the time corresponding to the start symbol of the first SSB to be transmitted as t3 based on the clock of a non-terrestrial network (such as a GNSS clock), and transmits (or broadcasts) t3 to the terminal. The terminal determines the start time of receiving the first SSB as t4 based on the clock of the non-terrestrial network (such as a GNSS clock), then the first transmission delay is equal to (t4-t3).

[0144] Optionally, the absolute time of the agreed signal transmitted by the first RAN node or the absolute time of the agreed moment can be directly indicated by information cells. For example, the absolute time information of the agreed signal can carry the information cell ReferenceTime shown in Table 1, which indicates the absolute time of the agreed signal. Similarly, the absolute time information of the agreed moment can carry the information cell ReferenceTime shown in Table 1, which indicates the absolute time of the agreed moment. Here, refDays represents days, refSeconds represents seconds, refMilliSeconds represents milliseconds, and refTenNanoSeconds represents nanoseconds. Therefore, the terminal can determine that the absolute time indicated by the above absolute time information is equal to: refDays*86400*1000*100000+refSeconds*1000*100000+refMilliSeconds*100000+refTenNanoSeconds. Alternatively, the above absolute time information can indicate the absolute time of the agreed signal transmitted by the first RAN node or the absolute time of the agreed moment by carrying a reference point and a time delay. This delay is either the absolute time between the first RAN node sending the agreed signal and the reference point, or the absolute time between the agreed moment and the reference point.

[0145] Table 1

[0146] Method 1.3: The first transmission delay is determined based on the first transmission distance. The first transmission distance is the distance between the terminal and the first RAN node. For example, the first transmission delay equals the first transmission distance (hereinafter denoted as D1) divided by the speed of light (c), such as: td1 = D1 / c. The process by which the terminal determines the first transmission distance is described below.

[0147] Optionally, the first transmission distance is determined based on a first time difference, a second transmission distance, a first downlink timing, and a second downlink timing. The second transmission distance is the distance between the terminal and the second RAN node. The second downlink timing is the downlink timing of the terminal for the second cell, and can be used by the terminal to determine the time or moment to receive downlink signals from the second RAN node.

[0148] Understandably, due to the timing deviation between the first RAN node and the second RAN node (such as the first time difference mentioned above), and the different first and second transmission distances, the first downlink timing and the second downlink timing are not aligned in absolute time. In other words, there is a deviation between the first and second downlink timings, which will be denoted as f1 below. For example, as shown in Figure 5B, f1, the first transmission distance, the first time difference (hereinafter referred to as f2), and the second transmission distance (hereinafter referred to as D2) can satisfy the following relationship: f1=[(D1-D2) / c]+f2 (Formula 1)

[0149] Where f1 = first downlink timing - second downlink timing, f2 = timing of the first cell - timing of the second cell, " / " represents division, and c represents the speed of light. (D1 / c) is the first transmission delay, and (D2 / c) is the second transmission delay. That is, the first transmission distance in this application can be reflected by the first transmission delay, and the second transmission distance can be reflected by the second transmission delay. The second transmission delay is the transmission delay between the terminal and the second cell, or the transmission delay between the terminal and the second RAN node. It can be understood that [(D1-D2) / c] can represent the difference in transmission delay between the terminal for the first cell and the second cell.

[0150] It is understandable that Formula 1 is merely an example of the relationship satisfied by f1, D1, f2, and D2. In specific applications, Formula 1 can also be transformed in various ways. For example, after transforming Formula 1, we can obtain Formula 2: f1 + (D2 / c) = f2 + (D1 / c). As another example, since (D2 / c) is the second transmission delay, Formula 1 can be transformed into Formula 3: f1 = [(D1 / c) - td2] + f2, where td2 is the second transmission delay. As yet another example, since (D1 / c) is the first transmission delay, Formula 1 can also be transformed into Formula 4: f1 = [td1 - (D2 / c)] + f2, or into Formula 5: f1 = td1 - td2 + f2. Furthermore, Figure 5B is drawn with f1 and f2 both being positive numbers, but in specific applications, f1 and f2 can also be negative numbers without restriction.

[0151] Understandably, for formulas 1 and 2, given f1, f2, and D2, the terminal can determine D1, and then determine td1 based on D1. For formula 3, given f1, f2, and td2, the terminal can determine D1, and then determine td1 based on D1. For formula 4, given f1, f2, and D2, the terminal can determine td1. For formula 5, given f1, f2, and td2, the terminal can determine td1. Here, f1 = first downlink timing - second downlink timing. Therefore, the terminal also needs to determine the second transmission distance (or second transmission delay), the second downlink timing, the first downlink timing, and the first time difference. The method by which the terminal determines the first time difference will be explained in S3011 to S3015 below, and will not be repeated here. The following describes the method by which the terminal determines the second transmission distance, the second transmission delay, the second downlink timing, and the first downlink timing.

[0152] Optionally, the terminal can determine the second transmission distance based on a timing advance command sent by the second RAN node. For example, the timing advance command can instruct the second RAN to determine a timing advance (TA) for the terminal, which is related to D2. For example, TA and D2 satisfy the following relationship: TA = 2 × (D2 / c), where "×" represents a multiplication sign.

[0153] Optionally, the terminal can determine the second transmission delay based on the timing advance command sent by the second RAN node. For example, the timing advance command can instruct the second RAN to determine a timing advance amount for the terminal, which is related to td2. For example, TA and td2 satisfy the following relationship: TA = 2 × td2.

[0154] Optionally, the terminal can determine the second downlink timing based on the timing of the second clock and the second transmission delay. For example, if the second clock is a GNSS clock, the second downlink timing is the GNSS timing delayed by td2. Alternatively, the terminal can determine the second downlink timing based on the SSB sent by the second RAN node.

[0155] 2. The terminal determines the timing method for the first downlink.

[0156] One possible implementation is that the terminal determines the first downlink timing based on the timing of a first clock and a first transmission delay. For example, the first clock is a GNSS clock, and the first downlink timing is the GNSS timing delayed by td1.

[0157] Another possible implementation is that the terminal can determine the first downlink timing based on the SSB sent by the first RAN node. Optionally, to reduce handover latency, before the terminal hands over to the first RAN node, the second RAN node can obtain configuration information for configuring the SSB of the first RAN node from the first RAN node and send this configuration information to the terminal. Subsequently, the terminal can receive the SSB based on this configuration information to obtain the first downlink timing.

[0158] Understandably, besides the aforementioned determined first uplink timing method, the first uplink timing can also be determined based on the first time difference, the second transmission distance (or the second transmission delay), and the second uplink timing. The second uplink timing is the terminal's uplink timing for the second cell, and it can be used by the terminal to determine the time or moment to send an uplink signal to the second RAN node. The second uplink timing can be determined based on the second downlink timing and the second transmission delay; for example, the second uplink timing can be advanced by (2×td2). Alternatively, the second uplink timing can be determined based on the second downlink timing and the TA determined by the second RAN for the terminal. For example, the terminal can receive a TA command from the second RAN node, which instructs on the TA. Subsequently, the terminal can determine that the second uplink timing is advanced by the second downlink timing.

[0159] For example, as shown in Figure 5C, the deviation between the first and second uplink timings (hereinafter referred to as f3), D1, f2, and D2 can satisfy the following relationship: f3 = f2 - (D1 / c) + (D2 / c). It is understood that the above relationship can also have various variations similar to Formulas 1 to 5, which will not be elaborated further.

[0160] S303: The terminal communicates with the first RAN node based on the first uplink timing.

[0161] One possible implementation is that the terminal sends uplink information to the first cell or the first RAN node according to the first uplink timing.

[0162] Based on the method shown in Figure 3, the terminal can quickly determine the uplink timing for the first cell, thus skipping the random access procedure in the first cell. In related technologies, a four-step random access procedure requires four interactions between the terminal and the first RAN node, and a two-step random access procedure also requires two interactions between the terminal and the first RAN node. Therefore, the method shown in Figure 3 can effectively reduce the uplink synchronization latency of the terminal for the first cell, thereby reducing the cell handover latency.

[0163] Optionally, in one possible implementation of the method shown in Figure 3, the terminal can directly obtain the first time difference from the network side (such as the first RAN node or the second RAN node). Alternatively, the terminal can also obtain information for determining the first time difference from the first RAN node and / or the second RAN node, and determine the first time difference based on this information. For example, as shown in Figure 6, the above S301 may include S3011, or S3012, or S3013 to S3015. The above steps are described in detail below.

[0164] S301 Implementation Method 1:

[0165] S3011: The second RAN node sends the first time difference information to the terminal. Correspondingly, the terminal receives the first time difference information from the second RAN node.

[0166] In this application, the information about the first time difference can indicate the first time difference. For example, the information about the first time difference includes the first time difference itself. Another example is that the information about the first time difference includes the absolute value of the first time difference and first indication information. The first indication information is used to indicate whether the first time difference is positive or negative. Taking a 1-bit first indication information as an example, when the value of this 1-bit is "0", it indicates that the first time difference is negative; when the value of this 1-bit is "1", it indicates that the first time difference is positive, and vice versa.

[0167] Optionally, the information about the first time difference can be carried in a system message, an RRC message, or a MAC-CE message.

[0168] For example, the system message is an SIB. The SIB may include the identifier of at least one candidate cell, and the absolute timing offset between each candidate cell and the second cell. The at least one candidate cell includes the first cell.

[0169] For example, the RRC message is an RRC reconfiguration message. The RRC reconfiguration message may include the identifier of at least one candidate cell, and the timing offset between each candidate cell and a second cell. The at least one candidate cell includes a first cell. Optionally, to save signaling overhead, the RRC reconfiguration message may also include configuration information for configuring all or some of the candidate cells in the at least one candidate cell. This configuration information can be used by the terminal to measure all or some of the aforementioned candidate cells and report a measurement report.

[0170] For example, MAC-CE messages can be sent via unicast, multicast, or broadcast, without restriction. The MAC-CE message can be a dedicated message or a general message, without limitation. The MAC-CE message may include the identifier of at least one candidate cell, and the timing offset between each candidate cell and a second cell. The at least one candidate cell includes the first cell. For example, the format of the MAC-CE message can be as shown in Figure 7. In Figure 7, the MAC-CE message includes N bytes (octet, oct), each byte may include the identifier of a candidate cell (e.g., it can occupy 3 bits), and the timing offset between that candidate cell and the second cell (e.g., it can occupy 4 bits). Optionally, each byte may also include reserve bits (e.g., it can occupy 1 bit). Figure 7 shows the case where N is greater than 1; it should be understood that in specific applications, N can also be equal to 1.

[0171] Optionally, in one possible implementation of the method shown in Figure 3, the second RAN node can obtain the timing of the first cell from the first RAN node and determine the first time difference by combining it with the timing of the second cell. For example, as shown in Figure 6, the method shown in Figure 3 may further include the following steps:

[0172] S300a: The first RAN node sends the fourth information to the second RAN node. Correspondingly, the second RAN node receives the fourth information from the first RAN node.

[0173] In this application, the fourth information can indicate the timing of the first cell. For example, the fourth information includes the absolute time information of the agreed signal or the absolute time information of the agreed moment. The absolute time information of the agreed signal can be referred to the corresponding description in Method 1.1 above, and the absolute time information of the agreed moment can be referred to the corresponding description in Method 1.2 above, and will not be repeated here.

[0174] Optionally, the first RAN node may send fourth information to the second RAN node when the inter-site interface (such as the Xn interface) is established. For example, the fourth information may be carried in an Xn Setup Request message or an Xn Setup Response message. It should be understood that the Xn interface is merely an example of an interface name between RAN nodes; in specific applications, it may have other names, such as X2 in 4G networks or a new name in 6G networks, without limitation.

[0175] Optionally, the first RAN node may send fourth information to the second RAN node based on a request from the second RAN node. For example, the second RAN node sends sixth information to the first RAN node, which is used to request the fourth information. After receiving the sixth information, the first RAN node sends the fourth information to the second RAN node. For instance, the second RAN node may include the sixth information when requesting the configuration of the first cell from the first RAN node. The first RAN node includes the fourth information when sending the configuration of the first cell to the second RAN node.

[0176] S300b: The second RAN node determines the first time difference based on the fourth information and the timing of the second cell.

[0177] Understandably, after receiving the fourth information, the second RAN node can determine the first time difference based on the received absolute time information and the timing of the second cell.

[0178] For example, taking the fourth information as including the absolute time information of the agreed signal, where the agreed signal is the first SSB on the radio frame with index 0, if the absolute time information of the agreed signal indicates an absolute time of t1, and the second RAN node determines the absolute time of the first SSB on the radio frame with index 0 that it transmits based on the clock of a non-terrestrial network (such as a GNSS clock) as t2, then the second RAN node determines the first time difference as (t1-t2).

[0179] For example, if the fourth information includes the absolute time information of the agreed time, which is the start time of the radio frame with index 0, and the absolute time information of the agreed time indicates an absolute time of t3, and the second RAN node determines the start time of the radio frame with index 0 as t4 based on the clock of a non-terrestrial network (such as a GNSS clock), then the second RAN node determines the first time difference as (t3-t4).

[0180] Understandably, in Method 1 described above, the second RAN node can determine the first time difference and send this information to the terminal. However, in practical applications, the first RAN node can also determine the first time difference and send this information to the terminal. This will be explained in detail below.

[0181] Implementation method two of S301:

[0182] S3012: The first RAN node sends the first time difference information to the terminal. Correspondingly, the terminal receives the first time difference information from the first RAN node.

[0183] In this application, the information about the first time difference can indicate the first time difference. Optionally, the information about the first time difference can be carried in a system message. Specifically, please refer to the corresponding description in S3011 above.

[0184] Optionally, in one possible implementation of the method shown in Figure 3, the first RAN node can obtain the timing of the second cell from the second RAN node and determine the first time difference by combining it with the timing of the first cell. For example, as shown in Figure 6, the method shown in Figure 3 may further include the following steps:

[0185] S300c: The second RAN node sends the fifth message to the first RAN node. Correspondingly, the first RAN node receives the fifth message from the second RAN node.

[0186] In this application, the fifth information can indicate the timing of the second cell. For example, the fifth information includes the absolute time information of the agreed signal or the absolute time information of the agreed moment. The absolute time information of the agreed signal can be referred to the corresponding description in Method 1.1 above, and the absolute time information of the agreed moment can be referred to the corresponding description in Method 1.2 above, and will not be repeated here.

[0187] Optionally, the second RAN node may send the fifth information to the first RAN node when establishing an inter-site interface (such as the Xn interface). For example, the fifth information may be carried in an Xn establishment request message or an Xn establishment response message. Alternatively, the second RAN node may carry the fifth information when requesting configuration of the first cell from the first RAN node.

[0188] Optionally, the second RAN node may send a fifth message to the first RAN node based on a request from the first RAN node. For example, the first RAN node sends an eighth message to the second RAN node, which requests the fifth message. After receiving the eighth message, the second RAN node sends the fifth message back to the first RAN node.

[0189] S300d: The first RAN node determines the first time difference based on the fifth information and the timing of the first cell.

[0190] Understandably, after receiving the fifth information, the first RAN node can determine the first time difference based on the received absolute time information and the timing of the first cell. Specifically, the process in S300d is similar to the process in S300b where the second RAN node determines the first time difference; please refer to the corresponding description in S300b for details, which will not be elaborated upon here.

[0191] Understandably, in either Method 1 or Method 2 above, the first RAN node or the second RAN node can directly indicate the first time difference to the terminal. In specific applications, the first RAN node or the second RAN node can also indicate information to the terminal for determining the first time difference, and the terminal can determine the first time difference based on this information. For details, please refer to the description in Method 3 below.

[0192] S301 Implementation Method 3:

[0193] S3013: The first RAN node sends the first information to the terminal. Correspondingly, the terminal receives the first information from the first RAN node.

[0194] In this application, the first information indicates the timing of the first cell. It is understood that the content of the first information is similar to that of the fourth information; please refer to the description of the fourth information in this application.

[0195] One possible implementation is that the first RAN node can directly send the first information to the terminal. For example, the first information is carried in a system message sent by the first RAN node.

[0196] Optionally, the first RAN node may send first information to the terminal based on the terminal's request. For example, the terminal sends third information to the first RAN node, the third information being used to request the first information. After receiving the third information, the first RAN node sends the first information to the terminal.

[0197] As an example, the third information can be a preamble. For instance, the protocol can predefine at least one preamble, the purpose of which is to trigger the network side to provide absolute timing information (timing reference point). The terminal can carry one of these preambles in the third information. After receiving the third information, the first RAN node can determine to provide the terminal with absolute timing information, such as the timing of the first cell. It should be understood that the aforementioned preamble may not be defined by the protocol, but rather configured by the first RAN node. For example, the first RAN node can configure a dedicated preamble to trigger the network side to provide absolute timing information when sending the configuration of the first cell to the terminal.

[0198] As another example, the third information is sent using a wake-up signal (WUS). For instance, the protocol may predefine some time-frequency resources, and a wake-up signal occupying these resources can trigger the network side to provide absolute timing information (timing reference point). Therefore, after receiving the third information, the first RAN node can determine to provide absolute timing information to the terminal, such as the timing of the first cell. It should be understood that the purpose of the aforementioned time-frequency resources may not be defined by the protocol, but rather configured by the first RAN node. For example, the first RAN node may configure these time-frequency resources when sending the configuration of the first cell to the terminal. It is understood that, in addition to the above methods, the wake-up signal can directly carry indication information to instruct the network side to provide absolute timing information. This indication information can be included in existing fields of the wake-up signal, or in reserved fields, or in new fields, without limitation. The aforementioned "fields" can also be replaced with "domains".

[0199] Another possible implementation is that the first RAN node first sends the first information to the second RAN node, and the second RAN node then sends the first information to the terminal.

[0200] As an example, the first RAN node can send first information to the second RAN node when the inter-site interface is established. For example, the first information is carried in an Xn establishment request message or an Xn establishment response message.

[0201] Optionally, the first RAN node may send first information to the second RAN node based on a request from the second RAN node. For example, the second RAN node sends ninth information to the first RAN node, whereby the ninth information is used to request the first information. After receiving the ninth information, the first RAN node sends the first information to the second RAN node. For instance, the second RAN node may include the ninth information when requesting the configuration of the first cell from the first RAN node. The first RAN node includes the first information when sending the configuration of the first cell to the second RAN node.

[0202] S3014: The second RAN node sends the second information to the terminal. Correspondingly, the terminal receives the second information from the second RAN node.

[0203] In this application, the second information indicates the timing of the second cell. It is understood that the content of the second information is similar to that of the fifth information, and reference can be made to the description of the fifth information in this application.

[0204] One possible implementation is that the second RAN node can directly send the second information to the terminal. For example, the second information is carried within a system message sent by the second RAN node.

[0205] Optionally, the second RAN node can send second information to the terminal based on the terminal's request. For example, the terminal sends third information to the second RAN node, which is used to request the second information. After receiving the third information, the second RAN node sends the second information to the terminal. For example, the third information is a preamble, or the third information is sent using a wake-up signal. A detailed description of the third information can be found in the corresponding description in S3013, and will not be repeated here.

[0206] Another possible implementation is that the second RAN node first sends the second information to the first RAN node, and the first RAN node then sends the second information to the terminal.

[0207] As an example, the second RAN node can send second information to the first RAN node when the inter-site interface is established. For example, the second information is carried in an Xn establishment request message or an Xn establishment response message.

[0208] Optionally, the second RAN node may send second information to the first RAN node based on a request from the first RAN node. For example, the first RAN node sends tenth information to the second RAN node, which is used to request the second information. After receiving the tenth information, the second RAN node sends the second information back to the first RAN node. For instance, the second RAN node may include the second information when requesting the configuration of the first cell from the first RAN node.

[0209] Understandably, when the second RAN node sends the second information to the first RAN node first, the first RAN node can send the first and second information to the terminal. Optionally, the first RAN node can send the first and second information to the terminal based on a request from the terminal. For example, if the terminal sends the third information to the first RAN node, the first RAN node, after receiving the third information, will send the first and second information to the terminal. Similarly, when the first RAN node sends the first information to the second RAN node first, the second RAN node can send the first and second information to the terminal. Optionally, the second RAN node can send the first and second information to the terminal based on a request from the terminal. For example, if the terminal sends the third information to the second RAN node, the second RAN node, after receiving the third information, will send the first and second information to the terminal. Here, the third information can be used to request the first and second information. For example, the third information may be a preamble, or it may be sent using a wake-up signal. A detailed description of the third information can be found in the corresponding description in S3013, and will not be repeated here.

[0210] S3015: The terminal determines the first time difference based on the first information and the second information.

[0211] Understandably, the process by which the terminal determines the first time difference based on the first and second information is similar to the process in S300b where the second RAN node determines the first time difference based on the fourth information and the timing of the second cell. You can refer to the corresponding description in S300b, which will not be repeated here.

[0212] It is understandable that the methods shown in Figure 3 or Figure 6 above can be applied to various inter-site cell handover scenarios. To better understand the synchronization method provided in this application, the complete process of the synchronization method provided in this application will be introduced below using the LTM-based cell handover process as an example.

[0213] As shown in Figure 8, another synchronization method provided in this application may include the following steps:

[0214] S801: The terminal sends a measurement report to the second RAN node. Correspondingly, the second RAN node receives the measurement report from the terminal.

[0215] In this system, the second RAN node can be any RAN node in the communication system 1000 shown in Figure 1, and the terminal can be any terminal in the communication system 1000 that is connected to the second RAN node. The area covered by the first RAN node can be divided into multiple cells, and the terminal communicates with the second RAN node through one of the cells, such as the second cell. The description of the second cell can be found in the corresponding descriptions in the methods shown in Figures 3 and 6 above.

[0216] One possible design is that the measurement report includes the terminal's measurement results of the neighboring cells of the second cell, which may be L3 measurement results. The method provided in this application is illustrated below using a first cell whose neighboring cells include a first RAN node as an example. The first RAN node may be a different RAN node from the second RAN node in the communication system 1000 shown in Figure 1. In this case, the measurement report includes the signal quality of the first cell measured by the terminal. The description of the first cell can be found in the corresponding descriptions in the methods shown in Figures 3 and 6 above.

[0217] S802: The second RAN node obtains LTM configuration information.

[0218] For example, taking a measurement report that includes the signal quality of a first cell measured by the terminal as an example, if the signal quality of the first cell measured by the terminal is greater than or equal to a threshold, the second RAN node determines to initiate the acquisition of the LTM configuration of the first cell. For example, the second RAN node may request the configuration of the first cell for handover from the first RAN node.

[0219] Understandably, the second RAN node can obtain LTM configuration information from the first RAN node. This LTM configuration information may include the terminal's configuration in the first cell. It may also include measurement signal information from the first cell, such as the SSB index or CSI-RS information. It should be understood that if the second RAN node also determines to initiate LTM configuration retrieval from a cell other than the first cell, such as a third cell, then the second RAN node will also need to obtain the LTM configuration of the third cell.

[0220] Optionally, during the above process, the second RAN node may send at least one of the sixth, fifth, ninth, or second information from the method shown in Figure 6 to the first RAN node. Optionally, during the above process, the first RAN node may send the fourth or first information from the method shown in Figure 6 to the second RAN node.

[0221] S803: The second RAN node sends an RRC reconfiguration message to the terminal. Correspondingly, the terminal receives the RRC reconfiguration message from the second RAN node.

[0222] One possible design is that the RRC reconfiguration message includes the terminal's configuration in the first cell and information about the measurement signals in the first cell. Optionally, the RRC reconfiguration message can also configure certain preambles or certain time-frequency resources used to carry wake-up signals to trigger the network side to provide absolute timing information.

[0223] Optionally, the RRC reconfiguration message may also include information about the first time difference. Alternatively, the second RAN node may send the first time difference information to the terminal after S803, and this first time difference information may be carried in a MAC-CE message.

[0224] Optionally, in response to the RRC reconfiguration message, the terminal sends an RRC reconfiguration complete message to the second RAN node. Correspondingly, the second RAN node receives the RRC reconfiguration complete message from the terminal. After receiving the RRC reconfiguration complete message, the second RAN node can determine the content configured in the RRC reconfiguration message.

[0225] S804: The terminal measures all or part of the measurement signals in the measurement signals of the first cell.

[0226] Understandably, if the measurement signal of the first cell is SSB, the terminal can determine the first downlink timing based on the SSB. Alternatively, the terminal can determine the first transmission delay before S808, and determine the first downlink timing based on the first transmission delay and the timing of the first clock. The process by which the terminal determines the first transmission delay can be referred to the corresponding description in S302 above, and will not be repeated here.

[0227] S805: The terminal determines the first uplink timing based on the first time difference.

[0228] Understandably, the method by which the terminal determines the first uplink timing can be referred to the corresponding description in S302 above, and will not be repeated here.

[0229] Understandably, S805 can be executed before S808. For example, if the terminal receives the first time difference information in S803, the terminal can determine the first uplink timing before S806 or S807; if the terminal receives the first time difference information in S807, the terminal can determine the first uplink timing before S808.

[0230] S806: The terminal sends a measurement report to the second RAN node. Correspondingly, the second RAN node receives the measurement report from the terminal.

[0231] The aforementioned measurement report includes the measurement results of the measurement signal of the first cell, which are L1 measurement results.

[0232] S807: The second RAN node sends a cell switch command to the terminal. Correspondingly, the terminal receives the cell switch command from the second RAN node.

[0233] In one possible implementation, in response to an S806 measurement report, the second RAN node sends a handover command to the terminal. This handover command indicates a handover to the first cell. The handover command can be carried in an L2 message, such as a MAC-CE message. The MAC-CE message can also include an index of the first cell's configuration. Optionally, the MAC-CE message may also include information about the first time difference.

[0234] S808: The terminal switches to the first cell.

[0235] Understandably, after receiving the handover command, the terminal can switch to the first cell.

[0236] Understandably, since the terminal determines the first uplink timing in S805, the terminal does not need to initiate random access and can directly communicate with the first cell. When the terminal determines that the first RAN node has received the uplink data sent by the terminal, such as when the terminal receives an indication message sent by the first RAN node indicating that uplink data has been received, the terminal determines that the cell handover is complete.

[0237] Based on the method shown in Figure 8, the second RAN node can request the configuration of the first cell for handover from the first RAN node for LTM. The terminal can measure the signal quality of the first cell based on the configuration of the first cell. The terminal can also determine the uplink timing for the first cell based on the timing deviation between the first and second cells before handover, so the terminal can skip the random access process in the first cell to reduce the handover latency.

[0238] It is understood that the actions of the terminal, the first RAN node, or the second RAN node in the above steps can be executed by the processor 201 in the communication device 20 shown in Figure 2, which calls the application code stored in the memory 203. This application does not impose any restrictions on this.

[0239] The various embodiments mentioned above in this application can be combined without contradiction, and no limitation is imposed.

[0240] It should be understood that the applicable scenarios of the method provided in this application are not limited to terrestrial cellular communication scenarios, but may also include non-terrestrial communication scenarios, satellite communication scenarios, high altitude platform station (HAPS) communication scenarios, V2X communication scenarios, integrated access and backhaul (IAB) communication scenarios, reconfigurable intelligent surface (RIS) communication scenarios, etc.

[0241] The above mainly describes the solution provided in this application from the perspective of interaction between various network elements. Correspondingly, this application also provides a communication device, which can be a terminal in the above method embodiments, or a device containing the above terminal, or a component usable in a terminal; or, the communication device can be a RAN node (such as a first RAN node or a second RAN node) in the above method embodiments, or a device containing the above RAN node, or a component usable in a RAN node. It is understood that the above-mentioned terminal or RAN node, etc., includes hardware structures and / or software modules corresponding to the execution of each function in order to achieve the above functions. Those skilled in the art should readily recognize that, based on the unit and algorithm operations of the various examples described in conjunction with the embodiments disclosed herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed by hardware or by computer software driving hardware 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.

[0242] This application can divide the terminal or RAN node into functional modules based on the above method examples. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It is understood that the module division in this application is illustrative and only represents one logical functional division; other division methods may be used in actual implementation.

[0243] For example, when functional modules are integrated, Figure 9 shows a schematic diagram of a communication device 90. The communication device 90 includes an interface module 901 and a processing module 902. The interface module 901, also called an interface unit, is used to perform transmit and receive operations; for example, it can be an interface circuit, transceiver, or communication interface. The processing module 902, also called a processing unit, is used to perform operations other than transmit and receive operations; for example, it can be a processing circuit or a processor.

[0244] In some embodiments, the communication device 90 may further include a storage module (not shown in FIG9) for storing program instructions and data.

[0245] For example, the communication device 90 is used to implement the functions of a terminal. The communication device 90 is, for example, the terminal described in the embodiment shown in FIG3, the embodiment shown in FIG6, or the embodiment shown in FIG8.

[0246] The processing module 902 is used to obtain a first time difference. The first time difference is the timing deviation between a first cell and a second cell, where the first cell is the target cell for cell handover by the communication device 90, and the second cell is the source cell for cell handover by the communication device 90. For example, the processing module 902 can be used to execute S301.

[0247] The processing module 902 is further configured to determine a first uplink timing based on a first time difference. The first uplink timing is the uplink timing of the communication device 90 for the first cell. For example, the processing module 902 can be configured to execute S302.

[0248] The processing module 902 is also used to send uplink information to the first cell according to the first uplink timing control interface module 901. For example, the processing module 902 can also be used to execute S303.

[0249] When used to implement the functions of a terminal, for other functions that the communication device 90 can implement, please refer to the relevant descriptions of the embodiments shown in FIG3, FIG6, or FIG8, which will not be elaborated further.

[0250] Alternatively, by way of example, the communication device 90 is used to implement the functions of a first RAN node / second RAN node. The communication device 90 is, for example, the first RAN node described in the embodiment shown in FIG3, the first RAN node / second RAN node described in the embodiment shown in FIG6, or the first RAN node / second RAN node described in the embodiment shown in FIG8.

[0251] Interface module 901 is used to send information about a first time difference to the terminal. The first time difference is the timing deviation between a first cell and a second cell. The first cell is the target cell for the terminal's cell handover, and the second cell is the source cell for the handover. The first time difference is used by the terminal to determine a first uplink timing, which is the uplink timing for the terminal relative to the first cell. For example, interface module 901 can be used to execute S3011 or S3012.

[0252] When used to implement the functions of the first RAN node / second RAN node, for other functions that the communication device 90 can implement, please refer to the relevant descriptions of the embodiments shown in FIG3, FIG6, or FIG8, which will not be elaborated further.

[0253] In a simplified embodiment, those skilled in the art will recognize that the communication device 90 can take the form shown in FIG2. For example, the processor 201 in FIG2 can invoke computer execution instructions stored in memory 203 to cause the communication device 90 to execute the method described in the above-described method embodiment.

[0254] For example, the functions / implementation processes of the interface module 901 and processing module 902 in Figure 9 can be implemented by the processor 201 in Figure 2 calling computer execution instructions stored in memory 203. Alternatively, the functions / implementation processes of the processing module 902 in Figure 9 can be implemented by the processor 201 in Figure 2 calling computer execution instructions stored in memory 203, and the functions / implementation processes of the interface module 901 in Figure 9 can be implemented by the transceiver 202 in Figure 2.

[0255] It is understood that one or more of the above modules or units can be implemented by software, hardware, or a combination of both. When any of the above modules or units are implemented by software, the software exists as computer program instructions and is stored in memory. The processor can be used to execute the program instructions and implement the above method flow. The processor can be built into a system-on-a-chip (SoC) or ASIC, or it can be a separate semiconductor chip. In addition to the core that executes the software instructions for computation or processing, the processor may further include necessary hardware accelerators, such as field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), or logic circuits that implement dedicated logic operations.

[0256] When the above modules or units are implemented in hardware, the hardware can be any one or any combination of a CPU, microprocessor, digital signal processing (DSP) chip, microcontroller unit (MCU), artificial intelligence processor, ASIC, SoC, FPGA, PLD, application-specific digital circuit, hardware accelerator, or non-integrated discrete device, which can run the necessary software or perform the above method flow independently of software.

[0257] Optionally, this application also provides a chip system, including: at least one processor and an interface, wherein the at least one processor is coupled to a memory via the interface, and when the at least one processor executes a computer program or instructions in the memory, the method in any of the above method embodiments is executed. In one possible implementation, the chip system further includes a memory. Optionally, the chip system may be composed of chips or may include chips and other discrete devices; this application does not specifically limit this.

[0258] Optionally, this application also provides a computer-readable storage medium. All or part of the processes in the above method embodiments can be implemented by a computer program instructing related hardware. This program can be stored in the aforementioned computer-readable storage medium. When executed, the program can include the processes described in the above method embodiments. The computer-readable storage medium can be an internal storage unit of the communication device in any of the foregoing embodiments, such as the hard disk or memory of the communication device. The aforementioned computer-readable storage medium can also be an external storage device of the communication device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the communication device. Further, the aforementioned computer-readable storage medium can include both internal storage units and external storage devices of the communication device. The aforementioned computer-readable storage medium is used to store the aforementioned computer program and other programs and data required by the communication device. The aforementioned computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0259] Optionally, this application also provides a computer program product. All or part of the processes in the above method embodiments can be executed by a computer program instructing related hardware. This program can be stored in the above computer program product, and when executed, it can include the processes described in the above method embodiments.

[0260] Optionally, this application also provides computer instructions. All or part of the processes in the above method embodiments can be executed by computer instructions instructing related hardware (such as a computer, processor, terminal, or RAN node). The program can be stored in the aforementioned computer-readable storage medium or the aforementioned computer program product.

[0261] Optionally, this application also provides a communication system, including: a first RAN node and a terminal in the embodiment shown in FIG3.

[0262] Optionally, this application also provides a communication system, including: a first RAN node, a second RAN node, and a terminal in the embodiment shown in FIG6.

[0263] Optionally, this application also provides a communication system, including: a first RAN node, a second RAN node, and a terminal in the embodiment shown in FIG8.

[0264] Through the above description of the embodiments, those skilled in the art can clearly understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0265] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules or 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 device, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0266] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0267] Furthermore, 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. The integrated unit can be implemented in hardware or as a software functional unit.

[0268] It is understood that the message names or parameter names in the messages between various network elements in the above embodiments of this application are just examples, and other names may be used in the specific implementation. This application does not make any specific limitations on this.

[0269] It is understood that in this application, " / " can indicate that the objects before and after it are in an "or" relationship. For example, A / B can mean A or B. "And / or" can be used to describe three relationships between the related objects. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. Here, A and B can be singular or plural. Furthermore, expressions like "at least one of A, B, and C" or "at least one of A, B, or C" are generally used to indicate any of the following: A exists alone; B exists alone; C exists alone; A and B exist simultaneously; A and C exist simultaneously; B and C exist simultaneously; A, B, and C exist simultaneously. The above examples using three elements (A, B, and C) illustrate the optional entries for this item. When the expression contains more elements, its meaning can be obtained according to the aforementioned rules.

[0270] To facilitate the description of the technical solutions of this application, the terms "first" and "second" may be used to distinguish technical features with the same or similar functions. The terms "first" and "second" do not limit the number or execution order, nor do they imply that they are necessarily different. In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" should not be construed as being more preferred or advantageous than other embodiments or design schemes. The use of "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner for ease of understanding.

[0271] It is understood that the term "embodiment" used throughout the specification means that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, various embodiments throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It is understood that in the various embodiments of this application, the sequence number of each process does not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this application.

[0272] It is understood that in this application, "when," "under the circumstances," "if," and "if" all refer to the corresponding processing that will be carried out under certain objective circumstances, and are not time-limited, nor do they require that there must be a judgment action when implemented, nor do they imply any other limitations.

[0273] It is understood that some optional features in this application can be implemented independently in certain scenarios without relying on other features, such as the current solution upon which they are based, to solve the corresponding technical problems and achieve the corresponding effects. Alternatively, they can be combined with other features as needed in certain scenarios. Correspondingly, the apparatus provided in this application can also implement these features or functions, which will not be elaborated here.

[0274] It is understood that the same step or step with the same function or technical feature in this application can be referenced and learned from each other in different embodiments.

[0275] It is understood that in this application, the first RAN node, and / or the second RAN node, and / or the terminal may perform some or all of the steps in this application. These steps are merely examples, and this application may also perform other steps or variations thereof. Furthermore, the steps may be performed in different orders as presented in this application, and it is possible that not all steps in this application need to be performed.

[0276] The above is only a specific embodiment of the present application, but the scope of protection of this application is not limited to this. Any changes or substitutions within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A synchronization method, characterized in that, The method includes: Obtain a first time difference, which is the timing deviation between the first cell and the second cell. The first cell is the target cell for the terminal to perform cell handover, and the second cell is the source cell for the terminal to perform cell handover. The first uplink timing is determined based on the first time difference, and the first uplink timing is the uplink timing of the terminal for the first cell; Uplink information is sent to the first cell according to the first uplink timing.

2. The method according to claim 1, characterized in that, The acquisition of the first time difference includes: Receive information about the first time difference.

3. The method according to claim 2, characterized in that, The information of the first time difference is carried in system messages, radio resource control messages, or media access control-control element messages.

4. The method according to claim 1, characterized in that, The acquisition of the first time difference includes: Receive first information and second information, wherein the first information indicates the timing of the first cell and the second information indicates the timing of the second cell; The first time difference is determined based on the first information and the second information.

5. The method according to claim 4, characterized in that, The method further includes: Send a third message, which is used to request at least one of the first message or the second message, wherein the third message is a preamble, or the third message is sent using a wake-up signal.

6. The method according to any one of claims 1-5, characterized in that, The first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

7. The method according to claim 6, characterized in that, The first transmission delay is determined based on the first transmission distance, which is the distance between the terminal and the first wireless access network node managing the first cell.

8. The method according to claim 7, characterized in that, The first transmission distance is determined based on the first time difference, the second transmission distance, the first downlink timing, and the second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

9. The method according to any one of claims 1-8, characterized in that, The wireless access network node that manages the first cell is different from the wireless access network node that manages the second cell.

10. The method according to any one of claims 1-9, characterized in that, The first time difference can be positive or negative.

11. A synchronization method, characterized in that, The method includes: Send information about a first time difference to the terminal. The first time difference is the timing deviation between the first cell and the second cell. The first cell is the target cell for the terminal to perform cell handover, and the second cell is the source cell for the terminal to perform cell handover. The first time difference is used by the terminal to determine the first uplink timing, which is the uplink timing of the terminal for the first cell.

12. The method according to claim 11, characterized in that, The first uplink timing is also related to the first transmission delay, which is the transmission delay between the terminal and the first cell.

13. The method according to claim 12, characterized in that, The first transmission delay is determined based on the first transmission distance, which is the distance between the terminal and the first wireless access network node managing the first cell.

14. The method according to claim 13, characterized in that, The first transmission distance is determined based on the first time difference, the second transmission distance, the first downlink timing, and the second downlink timing, wherein the second transmission distance is the distance between the terminal and the second radio access network node that manages the second cell, the first downlink timing is the downlink timing of the terminal for the first cell, and the second downlink timing is the downlink timing of the terminal for the second cell.

15. The method according to any one of claims 11-14, characterized in that, The method further includes: Receive fourth information from a first access network node, the first access network node being the access network node that manages the first cell, the fourth information indicating the timing of the first cell; The first time difference is determined based on the fourth information and the timing of the second cell.

16. The method according to any one of claims 11-15, characterized in that, The wireless access network node that manages the first cell is different from the wireless access network node that manages the second cell.

17. The method according to any one of claims 11-16, characterized in that, The first time difference can be positive or negative.

18. The method according to any one of claims 11-17, characterized in that, The information of the first time difference is carried in system messages, radio resource control messages, or media access control-control element messages.

19. A communication device, characterized in that, It includes units or modules for performing the method as described in any one of claims 1 to 10, or units or modules for performing the method as described in any one of claims 11 to 18.

20. A communication device, characterized in that, include: A processor coupled to a memory for storing a program or instructions which, when executed by the processor, cause the apparatus to perform the method as claimed in any one of claims 1 to 10, or the method as claimed in any one of claims 11 to 18.

21. A chip, characterized in that, include: A processor and an interface circuit, the interface circuit being configured to receive a computer program or instructions and transmit them to the processor, the processor being configured to execute the computer program or instructions, causing the chip to perform the method as claimed in any one of claims 1 to 10, or the method as claimed in any one of claims 11 to 18.

22. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed, they cause the computer to perform the method as described in any one of claims 1 to 10, or the method as described in any one of claims 11 to 18.

23. A computer program product, said computer program product comprising computer program code, characterized in that, When the computer program code is run on a computer, it causes the computer to implement the method of any one of claims 1 to 10, or the method of any one of claims 11 to 18.

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