A synchronization method and a communication device

Abstract

The present application provides a synchronization method and a communication device. The method includes: the first terminal uses other terminals as candidate synchronization reference sources with the highest synchronization priority. Since the terminal is relatively easy to deploy as a synchronization source, the first terminal can be synchronized to a certain terminal relatively easily, and there is no need to continuously search for other synchronization sources after synchronization, thereby reducing the power consumption of the terminal searching for the synchronization source. Compared with the method of giving priority to GNSS as the synchronization source or giving priority to the base station as the synchronization source, the synchronization method of the first synchronization type provided in the embodiment of the present application can complete synchronization more quickly and reduce the power consumption overhead caused by continuously searching for the synchronization source.

Description

[0001] This application claims the priority of a Chinese patent application with the application number 202110251216.5 and the invention title "A Sidelink Synchronization Method, Terminal and Network Device", which was filed with the State Intellectual Property Office of the People's Republic of China on March 8, 2021. The entire content of which is incorporated herein by reference. Technical Field

[0002] This application relates to the field of wireless communication technologies, and in particular, to a synchronization method and a communication device. Background Art

[0003] Before communication, a terminal needs to first search for a synchronization source and synchronize with the synchronization source.

[0004] Currently, one synchronization method is to perform synchronization based on the synchronization type of the global navigation satellite system (GNSS), that is, the terminal first searches for GNSS signals. If reliable GNSS signals can be found, synchronization is performed according to the GNSS signals. If reliable GNSS signals cannot be found, synchronization is first performed with a base station or other terminals. Subsequently, GNSS signals are still continuously searched until reliable GNSS signals are found and synchronized to the GNSS.

[0005] Another synchronization method is to perform synchronization based on the synchronization type of a base station, that is, the terminal first searches for base station signals. If reliable base station signals can be found, synchronization is performed according to the base station signals. If reliable base station signals cannot be found, synchronization is first performed with the GNSS or other terminals. Subsequently, base station signals are still continuously searched until reliable base station signals are found and synchronized to the base station.

[0006] However, in some scenarios, such as indoor scenarios, the terminal can never find base station signals or GNSS signals, resulting in the terminal continuously searching for a synchronization source, causing high power consumption of the terminal. Summary of the Invention

[0007] This application provides a synchronization method and a communication device to reduce the power consumption during terminal synchronization.

[0008] In a first aspect, an embodiment of the present application provides a synchronization method, which can be executed by a first terminal or a module applied in the first terminal. The method includes: detecting synchronization information from at least one candidate synchronization reference source, where the first terminal is a terminal that synchronizes based on a first synchronization type, and the first synchronization type uses a terminal as the candidate synchronization reference source with the highest synchronization priority. The at least one candidate synchronization reference source includes a second terminal, and the synchronization information of the at least one candidate synchronization reference source includes first synchronization information corresponding to the second terminal. The first synchronization information includes a first synchronization signal and a first indication information, and the first indication information indicates that the second terminal is the candidate synchronization reference source with the highest synchronization priority; synchronizing with the second terminal according to the first indication information and the first synchronization signal.

[0009] Based on the above solution, the first terminal uses other terminals as the candidate synchronization reference source with the highest synchronization priority. Since it is relatively easy to deploy terminals as synchronization sources, the first terminal can relatively easily synchronize to a certain terminal, thereby reducing the power consumption of the terminal searching for a synchronization source. Compared with the method of preferentially using GNSS as the synchronization source or preferentially using the base station as the synchronization source, the synchronization method of the first synchronization type provided by the embodiment of the present application can complete synchronization more quickly and reduce the power consumption overhead caused by continuously searching for a synchronization source.

[0010] In a possible implementation method, the at least one candidate synchronization reference source further includes at least one third terminal, and the synchronization information of the at least one candidate synchronization reference source further includes second synchronization information corresponding to the at least one third terminal respectively. The second synchronization information includes a second synchronization signal and a second indication information, and the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority; selecting the second terminal as the synchronization source from the second terminal and the at least one third terminal.

[0011] In a possible implementation method, the second terminal is selected as the synchronization source according to an upper layer indication of the first terminal. Here, the upper layer can also be understood as the high layer, such as the application layer. For example, the first terminal selects the second terminal as the synchronization source according to an indication of the application layer (which can be triggered by the user through an application or automatically triggered by the application layer).

[0012] In a possible implementation method, the second terminal is selected as the synchronization source according to the reference signal reception power between the first terminal and the second terminal, and the reference reception power between the first terminal and the at least one third terminal respectively. For example, if the reference signal reception power between the first terminal and the second terminal is the largest, the second terminal is selected as the synchronization source.

[0013] In a possible implementation method, if it is determined that a communication link can be successfully established between the first terminal and the second terminal, then the second terminal is selected as the synchronization source. For example, after the first terminal sends a communication link establishment request message to the second terminal, a communication link establishment request feedback message from the second terminal can be received, and then the first terminal determines that a communication link can be successfully established between the first terminal and the second terminal. For another example, the first terminal can receive a communication link establishment request message from the second terminal, and then the first terminal determines that a communication link can be successfully established between the first terminal and the second terminal.

[0014] In a possible implementation method, the detection of the synchronization information of other candidate synchronization reference sources except the second terminal is stopped.

[0015] Based on this solution, after the first terminal synchronizes with the second terminal, stopping the detection of the synchronization information of other candidate synchronization reference sources except the second terminal can reduce the power consumption of the first terminal.

[0016] In a possible implementation method, when the first condition is met, the first terminal re-detects the synchronization information of other candidate synchronization reference sources except the second terminal.

[0017] Based on the above solution, after the first terminal synchronizes with the second terminal, it does not need to continuously search for a synchronization source, but re-searches for a synchronization source only after the first condition is met, that is, re-detects the synchronization information of other candidate synchronization reference sources except the second terminal. Therefore, the power consumption of the terminal can be reduced.

[0018] In a possible implementation method, the at least one candidate synchronization reference source further includes at least one third terminal, the synchronization information of the at least one candidate synchronization reference source includes second synchronization information corresponding to the at least one third terminal respectively, the second synchronization information includes a second synchronization signal and second indication information, and the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority; based on the second indication information and the second synchronization signal, synchronization is performed with some or all of the at least one third terminal respectively.

[0019] In a possible implementation method, the first terminal stops detecting the synchronization information of other candidate synchronization reference sources except some or all of the second terminal and the at least one third terminal.

[0020] Based on this solution, after the first terminal synchronizes with the second terminal and the at least one third terminal, stopping the detection of the synchronization information of other candidate synchronization reference sources except some or all of the second terminal and the at least one third terminal can reduce the power consumption of the first terminal.

[0021] In a possible implementation method, when the first condition is satisfied, the first terminal re-detects the synchronization information of other candidate synchronization reference sources except for some or all of the second terminal and the at least one third terminal.

[0022] Based on the above solution, after the first terminal synchronizes with the second terminal and the at least one third terminal, it does not need to continuously search for a synchronization source, but re-searches for a synchronization source only after the first condition is satisfied, that is, re-detects the synchronization information of other candidate synchronization reference sources except for some or all of the second terminal and the at least one third terminal. Therefore, the power consumption of the terminal can be reduced.

[0023] In a possible implementation method, the first condition includes any one or more of the following: the received reference signal power between the first terminal and the second terminal is lower than a first threshold; or, the received reference signal power between the first terminal and the third terminal is lower than a first threshold; or, an upper layer of the first terminal indicates to re-search for a synchronization source; or, the establishment of a communication link between the first terminal and a fourth terminal fails; or, the first terminal receives information indicating to re-search for a synchronization source from the second terminal or the third terminal. Optionally, the information indicating to re-search for a synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source, and the synchronization deviation includes a time deviation and / or a frequency deviation.

[0024] In a possible implementation method, before synchronizing with the second terminal according to the first indication information and the first synchronization signal, it is determined that the received reference signal power between the first terminal and the second terminal is greater than a second threshold.

[0025] In a possible implementation method, after synchronizing with the second terminal according to the first indication information and the first synchronization signal, the third synchronization information is periodically sent, and the third synchronization information includes a third synchronization signal.

[0026] In a possible implementation method, the first indication information is carried on a broadcast channel.

[0027] In a possible implementation method, the first synchronization signal comes from a predefined set of synchronization signals.

[0028] The set of synchronization signals here is a set composed of synchronization signals predefined by the protocol, and this set of synchronization signals does not include newly added or custom synchronization signals. The synchronization signals in this set of synchronization signals can be detected and recognized not only by the first terminal in the embodiments of the present application, but also by terminals that are preferentially synchronized based on GNSS or base stations. Since the first terminal in the embodiments of the present application is configured to synchronize based on the first synchronization type, when the first terminal detects the first synchronization information, it can synchronize with the second terminal according to the first synchronization signal and the first indication information in the first synchronization signal. However, since the terminals that are preferentially synchronized based on GNSS or base stations are not preconfigured to synchronize based on the first synchronization type, when the terminals that are preferentially synchronized based on GNSS or base stations detect the first synchronization information, they may synchronize with the second terminal according to the first synchronization signal in the first synchronization information, but they may also synchronize with GNSS, base stations or other terminals.

[0029] Alternatively, the set of synchronization signals here contains both synchronization signals predefined by the protocol and newly added or custom synchronization signals. In this case, the synchronization signals predefined by the protocol in this set of synchronization signals can be detected and recognized by terminals that are preferentially synchronized based on GNSS or base stations, while the newly added or custom synchronization signals cannot be detected and recognized by terminals that are preferentially synchronized based on GNSS or base stations. Any synchronization signal in this set of synchronization signals can be detected and recognized by the first terminal.

[0030] Alternatively, the synchronization signal base station here only contains newly added or custom synchronization signals. In this case, the synchronization signals in this set of synchronization signals cannot be detected and recognized by terminals that are preferentially synchronized based on GNSS or base stations. Any synchronization signal in this set of synchronization signals can be detected and recognized by the first terminal.

[0031] Among them, in the embodiments of the present application, the protocol-predefined synchronization signal, which can also be referred to as the first type of synchronization signal, each first type of synchronization signal corresponds to a sidelink primary synchronization signal (SPSS) sequence and a sidelink secondary synchronization signal (SSSS) sequence. Among them, the combination of an SPSS sequence and an SSSS sequence corresponding to a synchronization signal can also be referred to as a synchronization identity (SSID). Therefore, it can also be understood that each first type of synchronization signal corresponds to an SSID. For example, the synchronization signal set includes 672 synchronization signals, each first type of synchronization signal corresponds to an SSID, and different first type of synchronization signals correspond to different SSIDs. Therefore, this synchronization signal set corresponds to 672 different SSIDs, such as the indexes are sequentially from 0 to 671, or sequentially from 1 to 672. Among them, the "newly added or user-defined synchronization signal" refers to the synchronization signal obtained by those skilled in the art or users by modifying the protocol-predefined synchronization signal or the synchronization signal generated according to a specific algorithm. The SSID corresponding to the newly added or user-defined synchronization signal is different from the SSID corresponding to the protocol-predefined synchronization signal. The newly added or user-defined synchronization signal, which can also be referred to as the second type of synchronization signal, the SSID corresponding to this second type of synchronization signal is different from the 672 SSIDs corresponding to the above first type of synchronization signal. Among them, the SSID corresponding to the second type of synchronization signal is different from the SSID corresponding to the first type of synchronization signal, which means that the PSSS in the two SSIDs is completely different or partially different, and / or the SSSS is completely different or partially different.

[0032] In a second aspect, embodiments of the present application provide a synchronization method, which can be executed by a second terminal or a module applied in the second terminal. The method includes: generating first indication information, where the first indication information indicates that the second terminal is the candidate synchronization reference source with the highest synchronization priority; periodically sending first synchronization information, where the first synchronization information includes a first synchronization signal and the first indication information.

[0033] Based on the above solution, the second terminal periodically sends the first synchronization information, so that the terminal with the second terminal as the candidate synchronization reference source with the highest synchronization priority can synchronize to the second terminal. Since it is relatively easy to deploy the second terminal as a synchronization source, the power consumption of other terminals searching for a synchronization source can be reduced.

[0034] In a possible implementation method, information indicating to re-search for a synchronization source is sent to a first terminal. Optionally, the information indicating to re-search for a synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source. The synchronization deviation includes a time and / or frequency deviation. The first terminal is a terminal that is synchronized with the second terminal.

[0035] In a possible implementation method, the first terminal is a terminal based on a first synchronization type, and the first synchronization type uses the terminal as the candidate synchronization reference source with the highest synchronization priority.

[0036] In a possible implementation method, the first indication information is carried on a broadcast channel.

[0037] In a possible implementation method, the first synchronization signal comes from a predefined set of synchronization signals.

[0038] In a third aspect, an embodiment of the present application provides a synchronization method, which can be executed by a second terminal or a module applied to the second terminal. The method includes: selecting a first synchronization signal from a first set of synchronization signals and periodically sending first-type synchronization information that includes the first synchronization signal; selecting a second synchronization signal from a second set of synchronization signals and periodically sending second-type synchronization information that includes the second synchronization signal; where the first set of synchronization signals includes one or more newly added or custom synchronization signals; the second set of synchronization signals includes one or more protocol-predefined synchronization signals.

[0039] Regarding the meanings of "newly added or custom synchronization signals" and "protocol-predefined synchronization signals", reference may be made to the foregoing description and will not be elaborated here.

[0040] Among them, a terminal that preferentially synchronizes based on GNSS or a base station cannot recognize the synchronization signals in the first set of synchronization signals, but can recognize the synchronization signals in the second set of synchronization signals. A terminal pre-configured to synchronize based on the first synchronization type can recognize both the synchronization signals in the first set of synchronization signals and the synchronization signals in the second set of synchronization signals. The meaning of a terminal that synchronizes based on the first synchronization type can be referred to the description in the foregoing first aspect. The terminal that synchronizes based on the first synchronization type can be, for example, the first terminal described in the foregoing first aspect.

[0041] Based on this solution, the second terminal can send a custom first synchronization signal and a predefined second synchronization signal simultaneously or alternately. Therefore, a terminal that gives priority to synchronizing based on GNSS or a base station can synchronize with the second terminal according to the second synchronization signal, while a terminal that synchronizes based on the first synchronization type can synchronize with the second terminal either according to the first synchronization signal or according to the second synchronization signal. This solution ensures that a terminal that synchronizes based on the first synchronization type can synchronize with the second terminal, while also being compatible with a terminal that gives priority to synchronizing based on GNSS or a base station to synchronize with the second terminal.

[0042] As an implementation method, the length of the transmission period of the first type of synchronization information is the same as the length of the transmission period of the second type of synchronization information, but the transmission time of the first type of synchronization information is different from the transmission time of the second type of synchronization information. Based on this solution, the second terminal alternately sends the first type of synchronization information and the second type of synchronization information according to the same transmission period length.

[0043] As another implementation method, the length of the transmission period of the first type of synchronization information is different from the length of the transmission period of the second type of synchronization information, and the transmission time of the first type of synchronization information is different from the transmission time of the second type of synchronization information. For example, the length of the transmission period of the first type of synchronization information is equal to twice the length of the transmission period of the second type of synchronization information. In this way, it can be achieved that within a certain period of time, the number of the second type of synchronization information sent is twice the number of the first type of synchronization information sent.

[0044] In a fourth aspect, an embodiment of the present application provides a synchronization method, which can be executed by a first terminal or a module applied in the first terminal. The method includes: detecting a first type of synchronization information from a second terminal, where the first type of synchronization information includes a first synchronization signal, and the first synchronization signal comes from a first synchronization signal set; determining that the first type of synchronization information cannot be recognized; detecting a second type of synchronization information from the second terminal, where the second type of synchronization information includes a second synchronization signal, and the second synchronization signal comes from a second synchronization signal set; synchronizing with the second terminal according to the second type of synchronization information; where the first synchronization signal set includes one or more newly added or custom synchronization signals; and the second synchronization signal set includes one or more protocol-predefined synchronization signals.

[0045] Among them, for the meanings of "newly added or custom synchronization signals" and "protocol-predefined synchronization signals", reference can be made to the foregoing description and will not be elaborated here.

[0046] The first terminal is a terminal that gives priority to synchronizing based on GNSS or a base station.

[0047] Based on this solution, if the first terminal cannot recognize the first synchronization signal, it continues to detect other synchronization signals. For example, when it detects a recognizable second synchronization signal, it synchronizes with the second terminal according to this second synchronization signal.

[0048] In a fifth aspect, an embodiment of the present application provides a synchronization method, which can be executed by a terminal or a module applied in the terminal. The method includes: searching for synchronization information from the terminal; when the synchronization information from the terminal is found, synchronizing according to the found synchronization information and stopping searching for the synchronization information from the terminal; or, when the synchronization information from the terminal is not found, continuously searching for the synchronization information from the terminal.

[0049] Based on this solution, the terminal continuously searches for synchronization information from other terminals until the synchronization information is found and synchronized with the terminal, which can achieve synchronization with the terminal as the synchronization source. Compared with the synchronization method that preferentially uses the base station or GNSS as the synchronization source, in the method of the embodiment of the present application, it is sometimes difficult for the terminal to search for a reliable base station signal or GNSS signal, but it is relatively easy to search for a reliable terminal signal, thereby reducing the power consumption caused by the terminal continuously searching for the synchronization source.

[0050] In a possible implementation method, when multiple synchronization information from multiple terminals is found, synchronize according to the multiple synchronization information.

[0051] In a possible implementation method, when multiple synchronization information from multiple terminals is found, select one synchronization information from the multiple synchronization information; synchronize according to the selected synchronization information.

[0052] In a possible implementation method, select the first synchronization information from the multiple synchronization information, and the reference signal receiving power of the terminal corresponding to the first synchronization information is the largest.

[0053] In a possible implementation method, after synchronizing according to the found synchronization information, the synchronization information is periodically sent.

[0054] In a possible implementation method, after stopping searching for the synchronization information from the terminal, when the trigger condition for re-searching the synchronization source is met, re-search for the synchronization information from the terminal.

[0055] In a possible implementation method, the trigger condition for re-searching the synchronization source includes any one or more of the following:

[0056] The reference signal receiving power of the synchronized terminal is lower than a preset threshold;

[0057] Receiving indication information from the synchronized terminal, and the indication information indicates re-searching the synchronization source; or,

[0058] It is determined that the establishment of the communication link with other terminals has failed.

[0059] In a fifth aspect, an embodiment of the present application provides a communication device, including a processor and an interface circuit. The interface circuit is configured to receive signals from other communication devices outside the communication device and transmit them to the processor, or send signals from the processor to other communication devices outside the communication device. The processor is configured to implement any of the implementation methods in the first aspect to the third aspect through logic circuits or by executing code instructions.

[0060] In a sixth aspect, an embodiment of the present application provides a communication device, including a processor coupled to a memory. The processor is configured to call a program stored in the memory to execute any of the implementation methods in the first aspect to the third aspect. The memory may be located inside the device or outside the device. And the processor may be one or more.

[0061] In a seventh aspect, an embodiment of the present application provides a communication device, including a processor and a memory; the memory stores computer instructions. When the communication device runs, the processor executes the computer instructions stored in the memory, so that the communication device executes any of the implementation methods in the first aspect to the third aspect.

[0062] In an eighth aspect, an embodiment of the present application provides a communication device, which may be a terminal or a module applied to a terminal. The device has the function of implementing any of the implementation methods in the first aspect to the third aspect. This function may be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0063] In a ninth aspect, an embodiment of the present application provides a communication device, including a module for executing any of the implementation methods in the first aspect to the third aspect.

[0064] In a tenth aspect, an embodiment of the present application provides a communication device for executing any of the implementation methods in the first aspect to the third aspect. The communication device is, for example, a terminal or a chip.

[0065] In an eleventh aspect, an embodiment of the present application provides a terminal for executing any of the implementation methods in the first aspect to the third aspect.

[0066] In a twelfth aspect, an embodiment of the present application further provides a computer program product, which includes a computer program. When the computer program is run by a processor, it implements any of the implementation methods in the first aspect to the third aspect.

[0067] In a thirteenth aspect, an embodiment of the present application further provides a computer-readable storage medium storing a computer program or instruction, which, when executed by a processor, implements any of the implementation methods in the first to third aspects described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 is a schematic diagram of the architecture of a communication system to which an embodiment of the present application is applied;

[0069] FIG. 2(a) is a schematic diagram of a synchronization method provided by an embodiment of the present application;

[0070] FIG. 2(b) is a schematic diagram of the relationship between the transmission period of the first type of synchronization information and the transmission period of the second type of synchronization information;

[0071] FIG. 2(c) is a schematic diagram of the comparison of the transmission periods of transmitting two types of synchronization information and only transmitting one type of synchronization information;

[0072] FIG. 2(d) is a schematic diagram of the comparison of the transmission periods of transmitting two types of synchronization information and only transmitting one type of synchronization information;

[0073] Figure 3 is a schematic diagram of a synchronization method provided by an embodiment of the present application;

[0074] Figure 4 is a schematic diagram of a first type of terminal transmitting synchronization information;

[0075] FIG. 5(a) is a schematic diagram of the synchronization result of a second type of terminal;

[0076] FIG. 5(b) is a schematic diagram of the result of re-searching for a synchronization source;

[0077] Figure 6 is a schematic diagram of the structure of a communication device provided by an embodiment of the present application;

[0078] Figure 7 is a schematic diagram of the structure of a communication device provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0079] Figure 1 is a schematic diagram of the architecture of a communication system to which an embodiment of the present application is applied. As Figure 1 shown, the communication system 1000 includes a radio access network 100 and a core network 200. Optionally, the communication system 1000 may further include the Internet 300. Among them, the radio access network 100 may include at least one radio access network device (such as Figure 1 110a and 110b in Figure 1among 120a - 120j). The terminal is connected to the radio access network device wirelessly, and the radio access network device is connected to the core network by wireless or wired means. The core network device and the radio access network device can be independent different physical devices, or the functions of the core network device and the logical functions of the radio access network device can be integrated on the same physical device, or the functions of part of the core network device and part of the radio access network device can be integrated on a physical device. Terminals can be connected to each other, and radio access network devices can be connected to each other, either by wire or wirelessly. Figure 1 It is only a schematic diagram, and other network devices may also be included in this communication system, such as wireless relay devices and wireless backhaul devices, which are not drawn in Figure 1 it.

[0080] The radio access network device can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next generation NodeB (gNB) in a 5th generation (5G) mobile communication system, a next generation NodeB in a 6th generation (6G) mobile communication system, a base station in a future mobile communication system, or an access node in a wireless fidelity (WiFi) system, etc.; it can also be a module or unit that completes part of the base station functions. For example, it can be a central unit (CU) or a distributed unit (DU). The radio access network device can be a macro base station (such as Figure 1 110a in Figure 1 ), or a micro base station or an indoor station (such as

[0081] A terminal can also be referred to as a terminal device, user equipment (UE), mobile station, mobile terminal, etc. Terminals can be widely applied in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearables, smart transportation, smart city, etc. A terminal can be a mobile phone, a tablet computer, a computer with wireless transceiver function, a wearable device, a vehicle, a drone, a helicopter, an airplane, a ship, a robot, a robotic arm, a smart home device, etc. Embodiments of this application do not limit the specific technologies and specific device forms adopted by the terminal.

[0082] The base station and the terminal can be fixed or movable. The base station and the terminal can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; and can also be deployed on airplanes, balloons, and artificial satellites in the air. Embodiments of this application do not limit the application scenarios of the base station and the terminal.

[0083] The roles of the base station and the terminal can be relative. For example, Figure 1 the helicopter or drone 120i in [reference] can be configured as a mobile base station. For the terminals 120j that access the radio access network 100 through 120i, the terminal 120i is a base station; but for the base station 110a, 120i is a terminal, that is, the communication between 110a and 120i is through the radio air interface protocol. Of course, the communication between 110a and 120i can also be through the interface protocol between base stations. At this time, relative to 110a, 120i is also a base station. Therefore, both the base station and the terminal can be uniformly referred to as communication devices. Figure 1 The 110a and 110b in [reference] can be referred to as communication devices with base station functions. Figure 1 The 120a - 120j in [reference] can be referred to as communication devices with terminal functions.

[0084] Communication can be carried out between a base station and a terminal, between base stations, or between terminals through licensed spectrum, unlicensed spectrum, or both simultaneously; it can be carried out through spectrum below 6 gigahertz (GHz), through spectrum above 6 GHz, or through both simultaneously. Embodiments of this application do not limit the spectrum resources used for wireless communication.

[0085] In embodiments of this application, the functions of a base station can also be performed by a module (such as a chip) in the base station or by a control subsystem that includes base station functions. The control subsystem that includes base station functions here can be a control center in application scenarios such as smart grids, industrial control, intelligent transportation, and smart cities. The functions of a terminal can also be performed by a module (such as a chip or modem) in the terminal or by a device that includes terminal functions.

[0086] Different from downlink (DL) communication and uplink (UL) communication in a cellular network, sidelink (SL) communication can support direct communication between terminals, that is, user data is directly transmitted between terminals, avoiding the transfer of user data through the network in cellular communication, thereby reducing transmission delay and alleviating network load. Among them, the sidelink can also be called a sidelink.

[0087] Synchronization is the basis for effective communication between terminals or between a terminal and a base station. There are two synchronization types in sidelink communication, namely, base station-based synchronization type and GNSS-based synchronization type. For terminals within the cellular coverage area (In-coverage), they can be configured with either the base station-based synchronization type or the GNSS-based synchronization type; for terminals outside the cellular coverage area (Out-of-coverage) or terminals without cellular communication capabilities, they can be configured with the GNSS-based synchronization type.

[0088] The synchronization process of a terminal includes the process of sending synchronization information and the process of selecting / reselecting a synchronization source.

[0089] The synchronization information here can be the Sidelink synchronization signal / physical sidelink broadcast channel block (S-SSB). The S-SSB consists of the SPSS, SSSS, and the physical sidelink broadcast channel (PSBCH). For example, the transmission period of the S-SSB is 160 milliseconds (ms), and multiple S-SSBs can be repeatedly transmitted within each period. 2 different PSSS sequences and 336 different SSSS sequences can form 672 different SSIDs, and the terminal can identify the SL SSID of other terminals by detecting the PSSS / SSSS transmitted by other terminals.

[0090] Among them, the process of the terminal transmitting synchronization information includes:

[0091] 1) If a terminal is within the coverage of the base station and is synchronized with the GNSS or the base station as the synchronization source, if the base station instructs the terminal to transmit synchronization information, or the base station does not instruct the terminal to transmit synchronization information but the terminal receives the Reference signal received power (RSRP) of the base station lower than the pre-configured threshold, then the terminal periodically transmits synchronization information.

[0092] 2) If a terminal is outside the coverage of the base station and is synchronized with the GNSS as the synchronization source, then the terminal periodically transmits synchronization information.

[0093] The terminal periodically transmits synchronization information so that other terminals can synchronize with the terminal.

[0094] 3) If a terminal is outside the coverage of the base station, not synchronized to the GNSS, not synchronized to the synchronization reference terminal, or the PSBCH-reference signal received power (PSBCH-RSRP) of the synchronization reference terminal is lower than the pre-configured threshold, then the terminal periodically transmits synchronization information.

[0095] This terminal is generally a terminal that is relatively far from the synchronization reference terminal. In order to enable more distant terminals to synchronize, this terminal can periodically transmit synchronization information so that more distant terminals can synchronize with this terminal.

[0096] Among them, for synchronization based on the GNSS synchronization type, the process of the terminal selecting / reselecting the synchronization source includes:

[0097] 1) If a terminal is configured for GNSS-based synchronization type, the terminal preferentially searches for GNSS signals. If GNSS is reliable, GNSS is selected as the synchronization source; if GNSS is unreliable, the synchronization source is reselected.

[0098] 2) If no reliable GNSS is found as the synchronization source, the terminal performs a full search to find the synchronization source, that is, searches all possible SL SSIDs in the synchronization information sent by other terminals, and / or searches the synchronization information sent by the base station. When one or more candidate synchronization reference sources are found, one candidate synchronization reference source is selected from the one or more candidate synchronization reference sources as the synchronization source according to the synchronization priority. Among them, the candidate synchronization reference source can be a terminal (also called a candidate synchronization reference terminal), or a base station.

[0099] In a possible implementation, the synchronization priorities of candidate synchronization reference sources are as follows:

[0100] a) Candidate synchronization reference sources with priority 1 (P1): Terminals directly synchronized to GNSS, that is, terminals that directly use GNSS as the synchronization source.

[0101] If there is only one terminal with P1, select this terminal as the synchronization source. If there are multiple terminals with P1, select the terminal with the largest PSBCH-RSRP from the multiple terminals with P1 as the synchronization source.

[0102] If there is no terminal with P1, perform the following b).

[0103] b) Candidate synchronization reference sources with priority 2 (P2): Terminals indirectly synchronized to GNSS, that is, terminals with P2 are synchronized with the terminal with P1 as the synchronization source.

[0104] If there is only one terminal with P2, select this terminal as the synchronization source. If there are multiple terminals with P2, select the terminal with the largest PSBCH-RSRP from the multiple terminals with P2 as the synchronization source.

[0105] If there is no terminal with P2, perform the following c).

[0106] c) Candidate synchronization reference sources with priority 3 (P3): Base stations.

[0107] If the synchronization signal of the base station can be detected, select this base station as the synchronization source.

[0108] If there is no candidate synchronization reference source with P3, perform the following d).

[0109] d) Candidate synchronization reference sources with priority 4 (P4): Terminals directly synchronized to the base station, i.e., terminals that directly use the base station as the synchronization source.

[0110] If there is only one P4 terminal, select this terminal as the synchronization source. If there are multiple P4 terminals, select the terminal with the largest PSBCH-RSRP from these multiple P4 terminals as the synchronization source.

[0111] If there is no P4 terminal, execute the following e).

[0112] e) Candidate synchronization reference sources with priority 5 (P5): Terminals indirectly synchronized to the base station, i.e., P5 terminals are synchronized using P4 terminals as the synchronization source.

[0113] If there is only one P5 terminal, select this terminal as the synchronization source. If there are multiple P5 terminals, select the terminal with the largest PSBCH-RSRP from these multiple P5 terminals as the synchronization source.

[0114] If there is no P5 terminal, execute the following f).

[0115] f) Candidate synchronization reference sources with priority 6 (P6): Terminals that can be used as synchronization sources other than P1 terminals, P2 terminals, P4 terminals, and P5 terminals.

[0116] If there is only one P6 terminal, select this terminal as the synchronization source. If there are multiple P6 terminals, select the terminal with the largest PSBCH-RSRP from these multiple P6 terminals as the synchronization source.

[0117] After synchronizing to a synchronization reference source, continuously perform exhaustive search. If a candidate synchronization reference source with a higher priority than the current synchronization reference source, or the same priority but a higher PSBCH-RSRP is found, reselect the synchronization source.

[0118] In another possible implementation, the synchronization priorities of candidate synchronization reference sources are as follows:

[0119] a) Candidate synchronization reference sources with priority 1 (P1): Terminals directly synchronized to GNSS, i.e., terminals that directly use GNSS as the synchronization source.

[0120] If there is only one P1 terminal, select this terminal as the synchronization source. If there are multiple P1 terminals, select the terminal with the largest PSBCH-RSRP from these multiple P1 terminals as the synchronization source.

[0121] If there is no terminal of P1, then perform the following b).

[0122] b) Candidate synchronization reference sources of priority 2 (P2): Terminals indirectly synchronized to GNSS, that is, the terminals of P2 are synchronized using the terminals of P1 as the synchronization source.

[0123] If there is only one terminal of P2, then select this terminal as the synchronization source. If there are multiple terminals of P2, then select the terminal with the largest PSBCH-RSRP from these multiple terminals of P2 as the synchronization source.

[0124] If there is no terminal of P2, then perform the following c).

[0125] c) Candidate synchronization reference sources of priority 3 (P3): Terminals other than the terminals of P1 and the terminals of P2 that can be used as synchronization sources.

[0126] If there is only one terminal of P3, then select this terminal as the synchronization source. If there are multiple terminals of P3, then select the terminal with the largest PSBCH-RSRP from these multiple terminals of P3 as the synchronization source.

[0127] After synchronizing to a synchronization reference terminal, continuously perform exhaustive search. If a candidate synchronization reference terminal with a higher priority than the current synchronization reference terminal, or the same priority but a higher PSBCH-RSRP is found, then reselect the synchronization source.

[0128] 3) If no reliable GNSS signal is found as the synchronization source, and no reliable synchronization reference terminal is found as the synchronization source, then the terminal uses itself as the synchronization source and continuously performs exhaustive search to find if there are other synchronization sources. If a candidate synchronization reference terminal is found, then reselect the synchronization source.

[0129] Among them, for synchronization based on the synchronization type of the base station, the process of the terminal selecting / reslecting the synchronization source includes:

[0130] 1) If a terminal is configured with the synchronization type based on the base station, then this terminal preferentially searches for the synchronization signal of the base station. If the synchronization signal of the base station can be searched, then select the base station as the synchronization source; if the synchronization signal of the base station cannot be detected, then reselect the synchronization source.

[0131] 2) If no base station is found as the synchronization source, the terminal performs a full search to find the synchronization source, that is, searches for all possible SL SSIDs in the synchronization information sent by other terminals, and / or searches for GNSS signals. When one or more candidate synchronization reference sources are found, one candidate synchronization reference source is selected from the one or more candidate synchronization reference sources as the synchronization source according to the synchronization priority. Among them, the candidate synchronization reference source can be a terminal (also known as a candidate synchronization reference terminal), or GNSS.

[0132] The synchronization priorities of the candidate synchronization reference sources are as follows:

[0133] a) Candidate synchronization reference sources with priority 1 (P1): Terminals directly synchronized to the base station, that is, terminals directly using the base station as the synchronization source.

[0134] If there is only one P1 terminal, select this terminal as the synchronization source. If there are multiple P1 terminals, select the terminal with the largest PSBCH-RSRP from the multiple P1 terminals as the synchronization source.

[0135] If there is no P1 terminal, execute the following b).

[0136] b) Candidate synchronization reference sources with priority 2 (P2): Terminals indirectly synchronized to the base station, that is, P2 terminals are synchronized using P1 terminals as the synchronization source.

[0137] If there is only one P2 terminal, select this terminal as the synchronization source. If there are multiple P2 terminals, select the terminal with the largest PSBCH-RSRP from the multiple P2 terminals as the synchronization source.

[0138] If there is no P2 terminal, execute the following c).

[0139] c) Candidate synchronization reference sources with priority 3 (P3): GNSS.

[0140] If a reliable GNSS signal can be detected, select GNSS as the synchronization source.

[0141] If there is no P3 candidate synchronization reference source, execute the following d).

[0142] d) Candidate synchronization reference sources with priority 4 (P4): Terminals directly synchronized to GNSS, that is, terminals directly using GNSS as the synchronization source.

[0143] If there is only one terminal of P4, select this terminal as the synchronization source. If there are multiple terminals of P4, select the terminal with the largest PSBCH-RSRP from these multiple terminals of P4 as the synchronization source.

[0144] If there is no terminal of P4, perform the following e).

[0145] e) Candidate synchronization reference source of priority 5 (P5): A terminal indirectly synchronized to GNSS, that is, a terminal of P5 is synchronized with a terminal of P4 as the synchronization source.

[0146] If there is only one terminal of P5, select this terminal as the synchronization source. If there are multiple terminals of P5, select the terminal with the largest PSBCH-RSRP from these multiple terminals of P5 as the synchronization source.

[0147] If there is no terminal of P5, perform the following f).

[0148] f) Candidate synchronization reference source of priority 6 (P6): Terminals other than terminals of P1, P2, P4, and P5 that can be used as synchronization sources.

[0149] If there is only one terminal of P6, select this terminal as the synchronization source. If there are multiple terminals of P6, select the terminal with the largest PSBCH-RSRP from these multiple terminals of P6 as the synchronization source.

[0150] After synchronizing to a synchronization reference source, continuously perform exhaustive search. If a candidate synchronization reference source with a higher priority than the current synchronization reference source, or the same priority but a higher PSBCH-RSRP is found, reselect the synchronization source.

[0151] In the GNSS-based synchronization type, as long as the terminal is not synchronized to GNSS, exhaustive search is required to find a synchronization source; in the base station-based synchronization type, as long as the terminal is not synchronized to the base station, exhaustive search is required to find a synchronization source. For scenarios such as indoors where GNSS signals are weak and there is no cellular network assistance (such as commercial scenarios like wearables and smart homes), the terminal will probably need to perform exhaustive search, resulting in high power consumption. Especially for power-constrained terminals such as watches and glasses, the power consumption generated during the synchronization process will account for a relatively large proportion of the total power consumption. Therefore, a more effective sidelink synchronization mechanism needs to be designed to reduce the power consumption generated during the synchronization process.

[0152] To solve the above problems, in the embodiments of the present application, terminals are divided into terminals of the first type and terminals of the second type. Among them, the terminals of the first type can also be referred to as group headers (GHs) or head terminals, and the terminals of the second type can also be referred to as group members (GMs) or member terminals. Among them, the terminals of the first type can be terminals with relatively large battery capacity or unrestricted power, such as terminals with relatively strong capabilities (such as mobile phones) or terminals powered by wire (such as large screens). The terminals of the second type can be terminals with power limitations, such as wearable devices (such as smart glasses and smart watches).

[0153] The terminals of the first type can be synchronized to the base station, GNSS, or other terminals according to the synchronization methods described above (i.e., synchronization based on the synchronization type of the base station or synchronization based on the GNSS synchronization type). The terminals of the first type can be used as synchronization sources and periodically broadcast synchronization information, so that the terminals of the second type are synchronized to the terminals of the first type. That is, the terminals of the second type are synchronized with the terminals of the first type as the synchronization source. The second terminal and at least one third terminal described later in this application are examples of the terminals of the first type.

[0154] The terminals of the second type are preconfigured to be synchronized based on the first synchronization type, where the first synchronization type uses the terminal as the candidate synchronization reference source with the highest synchronization priority. In the embodiments of the present application, the terminals of the second type use the terminals of the first type as the candidate synchronization reference source with the highest synchronization priority. Based on the synchronization method of the first synchronization type, if the terminals of the second type have been synchronized to a certain terminal of the first type, they will no longer continuously search for a synchronization source. If they have not been synchronized to a certain terminal of the first type, they need to continuously search for a synchronization source. The synchronization methods based on GNSS or the base station described above give priority to GNSS or the base station as the synchronization source. If synchronized to GNSS or the base station, they will no longer continuously search for a synchronization source. If not synchronized to GNSS or the base station, they need to continuously search for a synchronization source. Compared with the synchronization methods based on GNSS or the base station, the synchronization method of the first synchronization type provided in the embodiments of the present application can complete the synchronization of terminals more quickly when the coverage of GNSS or the base station is limited, and thus can reduce the power consumption overhead caused by continuously searching for a synchronization source. The first terminal described later in this application is an example of the terminals of the second type.

[0155] Referring to Fig. 2(a), the embodiments of the present application provide a synchronization method, which includes the following steps:

[0156] Step 201, the first terminal detects synchronization information from at least one candidate synchronization reference source.

[0157] The detection in the embodiments of the present application can also be understood as searching, and the two have the same meaning.

[0158] The first terminal here is a terminal of the second type. That is, the first terminal is a terminal based on the first synchronization type.

[0159] The candidate synchronization reference source can be GNSS, a base station, a terminal, etc. The terminal can be a terminal of the first type, a terminal of the second type, or a terminal that preferentially synchronizes based on GNSS or a base station.

[0160] The at least one candidate synchronization reference source includes a second terminal, and the second terminal is a terminal of the first type. The synchronization information of the at least one candidate synchronization reference source includes first synchronization information corresponding to the second terminal. The first synchronization information includes a first synchronization signal and first indication information. The first indication information indicates that the second terminal is the candidate synchronization reference source with the highest synchronization priority, or the first indication information indicates that the second terminal is a terminal of the first type, or the first indication information indicates that the second terminal is a head terminal, or the first indication information indicates that the second terminal is a terminal with unrestricted power.

[0161] Step 202, the first terminal synchronizes with the second terminal according to the first indication information and the first synchronization signal.

[0162] The first terminal learns, according to the first indication information, that the second terminal is a terminal of the first type. Or, the first terminal determines, according to the second indication information, that the second terminal is the candidate synchronization reference source with the highest synchronization priority. And since the first terminal is pre-configured to synchronize based on the first synchronization type, the first terminal can synchronize with the second terminal.

[0163] As an implementation method, after the first terminal obtains the first synchronization information sent by the second terminal, it can synchronize with the second terminal according to the first synchronization signal carried in the first synchronization information. Optionally, the first indication information is carried on a broadcast channel. Wherein, when the first synchronization information is S-SSB, the S-SSB is composed of SSSS, PSSS, and PSBCH. The combination of SSSS and PSSS is the first synchronization signal, and the first indication information is carried in the PSBCH. The PSBCH is an example of the above-mentioned broadcast channel.

[0164] Through the above solution, the first terminal uses other terminals as the candidate synchronization reference source with the highest synchronization priority. Since it is relatively easy to deploy terminals as synchronization sources, the first terminal can relatively easily synchronize to a certain terminal, thereby reducing the power consumption of the terminal searching for a synchronization source. Compared with the method of preferentially using GNSS as the synchronization source or preferentially using a base station as the synchronization source, the synchronization method of the first synchronization type provided by the embodiments of the present application can complete synchronization more quickly and reduce the power consumption overhead caused by continuously searching for a synchronization source.

[0165] For example, in an indoor application scenario, the first terminal is a low-power device such as a wearable device, and the second terminal is a mobile phone. Since there is a high possibility that a mobile phone is deployed around the wearable device in an indoor environment, the wearable device can easily search for a mobile phone signal and select a certain mobile phone signal as a synchronization source for synchronization. However, if synchronization is performed based on the GNSS or base station synchronization type, it is very likely that the wearable device cannot search for a reliable GNSS signal or base station signal, resulting in the wearable device continuously searching for GNSS signals or base station signals, causing relatively high power consumption.

[0166] Taking the first type of terminal as the second terminal described above as an example, the synchronization process of the first type of terminal will be introduced, mainly including the process of sending synchronization information and the process of selecting / reselecting a synchronization source.

[0167] Among them, the process of the second terminal sending synchronization information includes:

[0168] The second terminal periodically sends synchronization information (also referred to as the first synchronization information in the embodiments of the present application). This synchronization information can be S-SSB. Figure 4 Schematic diagram of sending synchronization information for the first type of terminal. Terminal 1, Terminal 2, and Terminal 3 are all the first type of terminals (i.e., group heads). The first type of terminal periodically sends synchronization information. Among them, the first terminal can be Terminal 1, Terminal 2, or Terminal 3 here. And, Terminal 4, Terminal 5, Terminal 6, Terminal 7, Terminal 8, Terminal 9, and Terminal 10 are the second type of terminals (i.e., group members) respectively. Among them, the second type of terminal is pre-configured to synchronize based on the first type of terminal or synchronize according to the first synchronization type.

[0169] As an implementation method, to ensure compatibility with terminals that prioritize synchronization based on GNSS or base stations, the second terminal periodically sends the first type of synchronization information and periodically sends the second type of synchronization information. Among them, the synchronization signals in the first type of synchronization information come from the first synchronization signal set, which is a set composed of synchronization signals newly added or customized based on the synchronization signals predefined in the protocol. The synchronization signals in the first synchronization signal set cannot be recognized by terminals that prioritize synchronization based on GNSS or base stations, but can be recognized by the second type of terminals. The synchronization signals in the second type of synchronization information come from the second synchronization signal set, and the synchronization signals in the second synchronization signal set come from the synchronization signals predefined in the protocol. The synchronization signals in the second synchronization signal set can be recognized by terminals that prioritize synchronization based on GNSS or base stations and can also be recognized by the second type of terminals. Therefore, the second type of terminals can synchronize with the first type of terminals according to the first type of synchronization information or the second type of synchronization information. Terminals that prioritize synchronization based on GNSS or base stations can synchronize with the first type of terminals according to the second type of synchronization information. Among them, the meanings of "newly added or customized synchronization signals" and "synchronization signals predefined in the protocol" can refer to the foregoing descriptions and will not be elaborated here.

[0170] As an implementation method, the length of the transmission period of the first type of synchronization information is the same as the length of the transmission period of the second type of synchronization information, but the transmission time of the first type of synchronization information is different from the transmission time of the second type of synchronization information. Based on this scheme, the second terminal alternately sends the first type of synchronization information and the second type of synchronization information at the same transmission period length.

[0171] As another implementation method, the length of the transmission period of the first type of synchronization information is different from the length of the transmission period of the second type of synchronization information, and the transmission time of the first type of synchronization information is different from the transmission time of the second type of synchronization information. For example, the length of the transmission period of the first type of synchronization information is equal to twice the length of the transmission period of the second type of synchronization information. In this way, it can be achieved that within a certain period of time, the number of the second type of synchronization information sent is twice the number of the first type of synchronization information sent.

[0172] The following uses an example to illustrate the transmission periods of the above-mentioned first type of synchronization information and the second type of synchronization information. Fig. 2(b) is a schematic diagram showing the relationship between the transmission periods of the first type of synchronization information and the second type of synchronization information. In this example, the length of the transmission period of the first type of synchronization information (denoted as S1 in the figure) is equal to the length of the transmission period of the second type of synchronization information (denoted as S2 in the figure), both being T. Moreover, the first type of synchronization information and the second type of synchronization information are transmitted alternately, and the transmission time interval between two adjacent first type of synchronization information and the second type of synchronization information is T / 2. Therefore, when the first type of synchronization information and the second type of synchronization information are regarded as a whole, the transmission period is T / 2, that is, every T / 2, a first type of synchronization information or a second type of synchronization information will be transmitted.

[0173] As an implementation method, referring to Fig. 2(c), it is a schematic diagram comparing the transmission periods of transmitting two types of synchronization information and transmitting only one type of synchronization information. When the second terminal only transmits the first type of synchronization information and does not transmit the second type of synchronization information, the transmission period of the first type of synchronization information can be set to T. Similarly, when the second terminal only transmits the second type of synchronization information and does not transmit the first type of synchronization information, the transmission period of the second type of synchronization information can be set to T. Through this scheme, regardless of whether the second terminal transmits two types of synchronization information or only one type of synchronization information, the transmission period of the transmitted synchronization information can be kept unchanged, that is, both are T.

[0174] As another implementation method, referring to Fig. 2(d), it is a schematic diagram comparing the transmission periods of transmitting two types of synchronization information and transmitting only one type of synchronization information. When the second terminal only transmits the first type of synchronization information and does not transmit the second type of synchronization information, the transmission period of the first type of synchronization information can be set to T / 2. Similarly, when the second terminal only transmits the second type of synchronization information and does not transmit the first type of synchronization information, the transmission period of the second type of synchronization information can be set to T / 2. Through this scheme, when transmitting two types of synchronization information, if the first type of synchronization information and the second type of synchronization information are regarded as a whole, the transmission period is T / 2, that is, every T / 2, a first type of synchronization information or a second type of synchronization information will be transmitted, which is the same as the transmission period of transmitting only the first type of synchronization information or only the second type of synchronization information.

[0175] As another implementation method, to ensure compatibility with terminals that give priority to synchronizing based on GNSS or base stations, the synchronization signal (also referred to as the first synchronization signal in the embodiments of this application) in the synchronization information sent by the second terminal (also referred to as the first synchronization information in the embodiments of this application) is the same as the synchronization signal predefined by the protocol, or it can be stated as: the synchronization signal in the synchronization information sent by the second terminal comes from a predefined set of synchronization signals, and this set of synchronization signals is composed of the synchronization signals predefined by the protocol. Since the synchronization signal in the synchronization information sent by the second terminal is the same as the synchronization signal in the synchronization information sent by terminals that give priority to synchronizing based on GNSS or base stations, in order to enable the second type of terminal to identify whether the received synchronization information is sent by the first type of terminal or by terminals that give priority to synchronizing based on GNSS or base stations, an indication information (also referred to as the first indication information in the embodiments of this application) can be carried in the synchronization information sent by the second terminal, and the function of this first indication information refers to the relevant description in step 201 above.

[0176] Reference Figure 3 , a synchronization method provided by the embodiments of this application, the method includes the following steps:

[0177] Step 301, the second terminal generates the first indication information.

[0178] The function of this first indication information refers to the relevant description in step 201 above.

[0179] Step 302, the second terminal periodically sends the first synchronization information, and this first synchronization information includes the first synchronization signal and the first indication information.

[0180] Through the above solution, the second terminal periodically sends the first synchronization information, so that the terminal with the highest synchronization priority as the candidate synchronization reference source can be synchronized to the second terminal. Since it is relatively easy to deploy the second terminal as a synchronization source, the power consumption of other terminals searching for a synchronization source can be reduced.

[0181] Among them, the process of the second terminal selecting / reslecting a synchronization source includes:

[0182] The second terminal can synchronize based on the synchronization type of GNSS, that is, it preferentially selects GNSS as the synchronization source. If it fails to synchronize to GNSS, it can select a synchronization reference terminal or a base station for synchronization. Or, the second terminal synchronizes based on the synchronization type of the base station, that is, it preferentially selects the base station as the synchronization source. If it fails to synchronize to the base station, it can select a synchronization reference terminal or GNSS for synchronization.

[0183] When the second terminal meets the conditions for reselection of the synchronization source, the second terminal performs the reselection operation of the synchronization source. Moreover, after reselecting the synchronization source and before switching the synchronization source, the second terminal also sends information indicating to re-search for the synchronization source to the terminals synchronized to the second terminal. Optionally, the information indicating to re-search for the synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after switching the synchronization source, and the synchronization deviation includes time deviation and / or frequency deviation. The information indicating to re-search for the synchronization source is used to indicate the terminals synchronized to the second terminal to re-perform synchronization.

[0184] For example, when the information indicating to re-search for the synchronization source includes the synchronization signal after the second terminal switches the synchronization source, the terminals synchronized to the second terminal re-search for the synchronization information corresponding to the synchronization signal to achieve re-synchronization to the second terminal. For another example, when the information indicating to re-search for the synchronization source includes the synchronization deviation before and after switching the synchronization source, the terminals synchronized to the second terminal determine new synchronization parameters according to the synchronization parameters of the currently synchronized synchronization source and the synchronization deviation before and after switching, and perform synchronization according to the new synchronization parameters.

[0185] The following describes the synchronization process of the second type of terminal, mainly including the process of sending synchronization information and the process of selecting / reselecting the synchronization source.

[0186] In the embodiments of the present application, the second type of terminal can be divided into a terminal with a first capability specification and a terminal with a second capability specification. Among them, the first capability specification is greater than the second capability specification. The terminal with the first capability specification can also be used as a synchronization source to send synchronization information when meeting certain conditions. The terminal with the second capability specification does not act as a synchronization source to send synchronization information.

[0187] The following takes the second type of terminal as the above-mentioned first terminal as an example for illustration.

[0188] Among them, the process of the first terminal sending synchronization information includes:

[0189] 1) If the first terminal is a terminal with a first capability specification, when the first terminal has synchronized to a first type of terminal (such as the second terminal mentioned above) and there is a communication requirement between the first terminal and other terminals but they are not synchronized, resulting in the failure of establishing a communication link, the upper layer (also known as the high layer, such as the application layer of the first terminal) of the first terminal can trigger re - synchronization. For example, according to the indication of the upper layer, the first terminal periodically sends synchronization information (in the embodiments of this application, this synchronization information is also referred to as the third synchronization information, and the third synchronization information includes a third synchronization signal) until a communication link is successfully established between the first terminal and the other terminal. For example, when the other terminal successfully receives the communication link establishment request message sent by the first terminal, it indicates that the communication link is successfully established. Another example is that when the first terminal successfully receives the communication link establishment request feedback message sent by the other terminal, it indicates that the communication link is successfully established.

[0190] Based on this solution, the terminal with the first capability specification does not continuously send synchronization information periodically, but sends synchronization information only when certain conditions are met, thus reducing the power consumption of the terminal.

[0191] 2) If the first terminal is a terminal with a second capability specification, the first terminal does not act as a synchronization source to send synchronization information.

[0192] Based on this solution, the terminal with the second capability specification does not need to send synchronization information, thus reducing the power consumption of the terminal.

[0193] Among them, the process of the first terminal selecting / reslecting a synchronization source includes:

[0194] The process of the first terminal selecting a synchronization source can refer to the aforementioned steps 201 to 202. A more detailed description is as follows.

[0195] The first terminal is pre - configured to synchronize based on the first type of terminal or pre - configured to synchronize according to the first synchronization type. The first terminal searches for the synchronization information sent by the first type of terminal. If it searches for the synchronization information sent by multiple different first - type terminals, it maintains multiple synchronization sources according to the multiple synchronization information, or selects one synchronization information from the multiple synchronization information and synchronizes according to this synchronization information.

[0196] Exemplarily, in the above step 201, the first terminal detects the synchronization information of multiple candidate synchronization reference sources, where the multiple candidate synchronization reference sources include a second terminal and at least one third terminal, and the third terminal is also a terminal of the first type. The synchronization information sent by each third terminal includes the second synchronization information corresponding to the third terminal, and the second synchronization information includes a second synchronization signal and second indication information, where the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority, or the second indication information indicates that the third terminal is a terminal of the first type, or the second indication information indicates that the third terminal is a head terminal, or the second indication information indicates that the third terminal is a power-unconstrained terminal.

[0197] As an implementation method, the first terminal only selects one terminal of the first type as the synchronization source. For example, the first terminal selects the second terminal as the synchronization source from the second terminal and at least one third terminal. Among them, the method for the first terminal to select one terminal of the first type can be any of the following methods:

[0198] Method A: The first terminal selects one from multiple terminals of the first type according to the upper-layer indication.

[0199] For example, the first terminal selects the second terminal as the synchronization source from the second terminal and at least one third terminal according to the upper-layer indication.

[0200] Method B: Select one from multiple terminals of the first type according to the communication requirements (such as whether a communication link can be successfully established or the communication quality requirements).

[0201] For example, if the first terminal determines that a communication link can be successfully established with the second terminal, it selects the second terminal as the synchronization source from the second terminal and at least one third terminal. For example, after the first terminal sends a communication link establishment request message to the second terminal, it can receive a communication link establishment request feedback message from the second terminal, then the first terminal determines that a communication link can be successfully established between the first terminal and the second terminal. For another example, the first terminal can receive a communication link establishment request message from the second terminal, then the first terminal determines that a communication link can be successfully established between the first terminal and the second terminal.

[0202] For another example, if the first terminal determines that the communication quality with the second terminal meets the requirements, it selects the second terminal as the synchronization source from the second terminal and at least one third terminal.

[0203] Method C: Select one from multiple terminals of the first type according to the reference signal received power (such as PSBCH-RSRP) between the first terminal and multiple terminals of the first type.

[0204] For example, the first terminal compares the reference signal reception power between the first terminal and multiple terminals of the first type, and selects the terminal of the first type with the maximum reference signal reception power. For example, the first terminal selects the second terminal as the synchronization source according to the reference signal reception power between the first terminal and the second terminal, and the reference reception power between the first terminal and each of the at least one third terminal. Specifically, if the first terminal determines that the reference signal reception power between the first terminal and the second terminal is the maximum, then the first terminal selects the second terminal as the synchronization source from the second terminal and the at least one third terminal.

[0205] Optionally, after synchronizing with the second terminal, the first terminal stops detecting the synchronization information of other candidate synchronization reference sources except the second terminal.

[0206] Suppose Figure 4 Each terminal of the second type synchronizes to only one terminal of the first type. FIG. 5(a) is a schematic diagram of the synchronization result of the terminals of the second type. Among them, terminal 4 and terminal 5 synchronize with terminal 1 as the synchronization source, terminal 6, terminal 7, terminal 8, and terminal 9 synchronize with terminal 2 as the synchronization source, and terminal 10 synchronizes with terminal 3 as the synchronization source. Among them, if multiple terminals of the second type synchronize to the same terminal of the first type, since the same synchronization source is adopted, these terminals of the second type can communicate with each other. Moreover, the terminals of the second type and the terminals of the first type can also communicate with each other. For example, terminal 4 can communicate with terminal 5, terminal 4 can communicate with terminal 1, and terminal 5 can communicate with terminal 1. If multiple terminals of the second type synchronize to different terminals of the first type, then these terminals of the second type may or may not be able to communicate with each other. For example, when terminal 1 and terminal 2 synchronize with the same synchronization source, terminal 4 (or terminal 5) can communicate with any one of terminals 6 to 9. For another example, when terminal 1 and terminal 2 synchronize with different synchronization sources, terminal 4 or terminal 5 cannot communicate with any one of terminals 6 to 9.

[0207] As another implementation method, the first terminal can also select multiple terminals of the first type as the synchronization source. For example, on the one hand, the first terminal synchronizes with the second terminal according to the above step 202, and on the other hand, the first terminal synchronizes with some or all of the at least one third terminal according to the second indication information and the second synchronization signal in the second synchronization information sent by the at least one third terminal. For example, if the first terminal detects the first synchronization information of the second terminal and the second synchronization information of five third terminals, then on the one hand, the first terminal synchronizes with the second terminal, and on the other hand, the first terminal can also synchronize with one or more of the five third terminals.

[0208] Optionally, after the first terminal synchronizes with some or all of the second terminal and at least one third terminal, the first terminal stops detecting the synchronization information of other candidate synchronization reference sources other than some or all of the second terminal and at least one third terminal.

[0209] If the first terminal does not search for a reliable terminal of the first type as the synchronization source, and when the first terminal is a terminal with the first capability specification, the first terminal continuously searches for the synchronization information sent by the terminal of the first type until it searches for the synchronization information sent by the terminal of the first type, or selects itself as the terminal of the first type for synchronization source selection. Among them, the specific implementation method for the first terminal to select itself as the terminal of the first type for synchronization source selection can refer to the implementation method for the terminal of the first type to select the synchronization source described above, and will not be elaborated here. If the first terminal does not search for a reliable terminal of the first type as the synchronization source, and when the first terminal is a terminal with the second capability specification, the first terminal continuously searches for the synchronization information sent by the terminal of the first type until it searches for the synchronization information sent by the terminal of the first type.

[0210] Based on the above solution, the first terminal uses the terminal of the first type as the synchronization source. If it synchronizes to a certain terminal of the first type, it will no longer continuously search for the synchronization source. If it does not synchronize to a certain terminal of the first type, it needs to continuously search for the synchronization source. Since the deployment of the terminal of the first type is relatively easy, the first terminal can relatively easily synchronize to a certain terminal of the first type, thereby reducing the power consumption of the terminal continuously searching for the synchronization source. Compared with the method of preferentially using GNSS as the synchronization source or preferentially using the base station as the synchronization source, the synchronization method provided by the embodiments of the present application can complete synchronization more quickly, and thus can reduce the power consumption overhead caused by continuously searching for the synchronization source.

[0211] It should be noted that before the first terminal searches for the synchronization information sent by the terminal of the first type, if it detects the GNSS signal or the synchronization signal of the base station, or the synchronization information sent by the terminal that preferentially synchronizes based on GNSS or the base station, the first terminal can first synchronize to GNSS, the base station, or the terminal that preferentially synchronizes based on GNSS or the base station. Then, the first terminal can continuously search for the terminal of the first type subsequently until it re-synchronizes to the terminal of the first type.

[0212] After the first terminal synchronizes to one or more first - type first terminals, when the trigger condition for re - searching the synchronization source (hereinafter referred to as the first condition) is met, the first terminal re - searches the synchronization source; otherwise, there is no need to re - search the synchronization source. For example, when the first terminal only synchronizes to the second terminal, when the first condition is met, the first terminal re - detects the synchronization information of other candidate synchronization reference sources except the second terminal. Another example is that when the first terminal synchronizes to some or all of the second terminal and at least one third terminal, when the first condition is met, the first terminal re - detects the synchronization information of other candidate synchronization reference sources except some or all of the second terminal and at least one third terminal.

[0213] Among them, the first condition includes any one or more combinations of the following:

[0214] a) The upper layer of the first terminal instructs to re - search the synchronization source;

[0215] b) The communication link between the first terminal and the fourth terminal fails to be established;

[0216] c) The reference signal receiving power (such as PSBCH - RSRP) between the first terminal and the second terminal is lower than the first threshold;

[0217] d) The reference signal receiving power (such as PSBCH - RSRP) between the first terminal and the third terminal is lower than the first threshold;

[0218] e) The first terminal receives information indicating to re - search the synchronization source from the second terminal. Optionally, the information indicating to re - search the synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source. The synchronization deviation includes time deviation and / or frequency deviation;

[0219] f) The first terminal receives information indicating to re - search the synchronization source from the third terminal. Optionally, the information indicating to re - search the synchronization source includes the synchronization signal after the third terminal switches the synchronization source and / or the synchronization deviation before and after the third terminal switches the synchronization source. The synchronization deviation includes time deviation and / or frequency deviation.

[0220] It should be noted that when the first terminal synchronizes with multiple terminals of the first type simultaneously, in the first implementation method, if the received reference signal power between one of the multiple terminals of the first type and the first terminal is lower than the first threshold, the first terminal is triggered to re-search for a synchronization source. In the second implementation method, when the received reference signal power between more than a preset number of terminals of the first type and the first terminal is lower than the first threshold, the first terminal is triggered to re-search for a synchronization source. In the third implementation method, when the received reference signal power between each of the multiple terminals of the first type and the first terminal is lower than the first threshold, the first terminal is triggered to re-search for a synchronization source.

[0221] Referring to FIG. 5(b), it is a schematic diagram of the result of re-searching for a synchronization source. In FIG. 5(a), terminal 9 synchronizes with terminal 2 as the synchronization source. When terminal 2 determines that the trigger condition for re-searching for a synchronization source is met, it re-searches for a synchronization source. For example, if it is determined that terminal 3 is the synchronization source, then terminal 9 switches from synchronizing with terminal 2 to synchronizing with terminal 3.

[0222] Based on the above solution, after the first terminal synchronizes with the terminals of the first type, it does not need to continuously search for a synchronization source, but only re-searches for a synchronization source when the trigger condition for re-searching for a synchronization source is met. Therefore, the power consumption of the terminal can be reduced.

[0223] As an implementation method, before the first terminal synchronizes with the second terminal according to the first indication information and the first synchronization signal, it also determines that the received reference signal power between the first terminal and the second terminal is greater than the second threshold. Before the first terminal synchronizes with the third terminal according to the second indication information and the second synchronization signal, it also determines that the received reference signal power between the first terminal and the third terminal is greater than the second threshold. That is, before the first terminal synchronizes with a certain terminal of the first type, it first determines that the received reference signal power of the terminal of the first type is greater than the second threshold. If the received reference signal power of a certain terminal of the first type is less than or equal to the second threshold, the first terminal does not synchronize with the terminal of the first type.

[0224] It can be understood that in order to implement the functions in the above embodiments, the base station and the terminal include the corresponding hardware structures and / or software modules for performing each function. Those skilled in the art should easily realize that, combining the units and method steps of each example described in the embodiments disclosed in the present application, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in the form of hardware or computer software driving hardware depends on the specific application scenario and design constraint conditions of the technical solution.

[0225] Figure 6 and Figure 7Schematic diagram of a possible communication device provided by an embodiment of the present application. These communication devices can be used to implement the functions of the terminal or the base station in the above method embodiments, and thus can also achieve the beneficial effects possessed by the above method embodiments. In the embodiments of the present application, the communication device may be one of the terminals 120a to 120j as shown in Figure 1 or may be the base station 110a or 110b as shown in Figure 1 , or may also be a module (such as a chip) applied to the terminal or the base station.

[0226] As shown in Figure 6 , the communication device 600 includes a processing unit 610 and a transceiver unit 620. The communication device 600 is used to implement the functions of the terminal or the base station in the above method embodiments.

[0227] When the communication device 600 is used to implement the function of the first terminal in the above method embodiments, the transceiver unit 620 is configured to receive synchronization information from at least one candidate synchronization reference source. The first terminal is a terminal that synchronizes based on a first synchronization type, and the first synchronization type uses the terminal as the candidate synchronization reference source with the highest synchronization priority. The at least one candidate synchronization reference source includes a second terminal. The synchronization information includes first synchronization information corresponding to the second terminal. The first synchronization information includes a first synchronization signal and a first indication information. The first indication information indicates that the second terminal is the candidate synchronization reference source with the highest synchronization priority. The processing unit 610 is configured to detect the synchronization information of the at least one candidate synchronization reference source, and synchronize with the second terminal according to the first indication information and the first synchronization signal.

[0228] In a possible implementation method, the at least one candidate synchronization reference source further includes at least one third terminal. The synchronization information of the at least one candidate synchronization reference source includes second synchronization information respectively corresponding to the at least one third terminal. The second synchronization information includes a second synchronization signal and a second indication information. The second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority. The processing unit 610 is further configured to select the second terminal as the synchronization source from the second terminal and the at least one third terminal.

[0229] In a possible implementation method, the processing unit 610 is specifically configured to select the second terminal as the synchronization source according to an upper layer indication; or select the second terminal as the synchronization source according to the reference signal received power between the first terminal and the second terminal, and the reference received power between the first terminal and the at least one third terminal respectively; or determine that a communication link can be successfully established between the first terminal and the second terminal, and then select the second terminal as the synchronization source.

[0230] In a possible implementation method, the transceiver unit 620 is further configured to stop detecting the synchronization information of other candidate synchronization reference sources except the second terminal.

[0231] In a possible implementation method, the transceiver unit 620 is further configured to, when a first condition is satisfied, re-detect the synchronization information of other candidate synchronization reference sources except the second terminal.

[0232] In a possible implementation method, the at least one candidate synchronization reference source further includes at least one third terminal, the synchronization information of the at least one candidate synchronization reference source includes second synchronization information corresponding to the at least one third terminal respectively, the second synchronization information includes a second synchronization signal and second indication information, and the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority; the processing unit 610 is further configured to perform synchronization with some or all of the at least one third terminal respectively according to the second indication information and the second synchronization signal.

[0233] In a possible implementation method, the transceiver unit 620 is further configured to stop detecting the synchronization information of other candidate synchronization reference sources except some or all of the second terminal and the at least one third terminal.

[0234] In a possible implementation method, the transceiver unit 620 is further configured to, when a first condition is satisfied, re-detect the synchronization information of other candidate synchronization reference sources except some or all of the second terminal and the at least one third terminal.

[0235] In a possible implementation method, the first condition includes any one or more of the following: the received signal power of the reference signal between the first terminal and the second terminal is lower than a first threshold; or, the received signal power of the reference signal between the first terminal and the third terminal is lower than the first threshold; or, the upper layer of the first terminal indicates to re-search for a synchronization source; or, the communication link establishment between the first terminal and the fourth terminal fails; or, the first terminal receives information indicating to re-search for a synchronization source from the second terminal or the third terminal. Optionally, the information indicating to re-search for a synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source, and the synchronization deviation includes a time deviation and / or a frequency deviation.

[0236] In a possible implementation method, the processing unit 610 is further configured to determine that the received signal power of the reference signal between the first terminal and the second terminal is greater than a second threshold before performing synchronization with the second terminal according to the first indication information and the first synchronization signal.

[0237] In a possible implementation method, the transceiver unit 620 is further configured to periodically send third synchronization information after the processing unit 610 synchronizes with the second terminal according to the first indication information and the first synchronization signal, where the third synchronization information includes a third synchronization signal.

[0238] In a possible implementation method, the first indication information is carried on a broadcast channel.

[0239] In a possible implementation method, the first synchronization signal is from a predefined set of synchronization signals.

[0240] When the communication device 600 is used for the function of the second terminal in the above method embodiment: The processing unit 610 is configured to generate first indication information, where the first indication information indicates that the second terminal is a candidate synchronization reference source with the highest synchronization priority; the transceiver unit 620 is configured to periodically send first synchronization information, where the first synchronization information includes a first synchronization signal and the first indication information.

[0241] In a possible implementation method, the transceiver unit 620 is further configured to send information indicating to re-search for a synchronization source to the first terminal. Optionally, the information indicating to re-search for a synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source, where the synchronization deviation includes a time and / or frequency deviation, and the first terminal is a terminal that is synchronized with the second terminal.

[0242] In a possible implementation method, the first terminal is a terminal based on a first synchronization type, and the first synchronization type uses the terminal as a candidate synchronization reference source with the highest synchronization priority.

[0243] In a possible implementation method, the first indication information is carried on a broadcast channel.

[0244] In a possible implementation method, the first synchronization signal is from a predefined set of synchronization signals.

[0245] When the communication device 600 is used for the function of the second terminal in the above method embodiment: The processing unit 610 is configured to select a first synchronization signal from a first set of synchronization signals, and the transceiver unit 620 is configured to periodically send the first synchronization signal; the processing unit 610 is further configured to select a second synchronization signal from a second set of synchronization signals, and the transceiver unit 620 is further configured to periodically send the second synchronization signal; where the first set of synchronization signals includes one or more newly added or custom synchronization signals; the second set of synchronization signals includes one or more predefined synchronization signals.

[0246] A more detailed description of the above-mentioned processing unit 610 and transceiver unit 620 can be directly obtained from the relevant descriptions in the above method embodiments, and will not be elaborated here.

[0247] As Figure 7 shown, the communication device 700 includes a processor 710 and an interface circuit 720. The processor 710 and the interface circuit 720 are coupled to each other. It can be understood that the interface circuit 720 can be a transceiver or an input / output interface. Optionally, the communication device 700 may further include a memory 730 for storing instructions executed by the processor 710 or storing input data required for the processor 710 to run instructions or storing data generated after the processor 710 runs instructions.

[0248] When the communication device 700 is used to implement the above method embodiments, the processor 710 is used to implement the functions of the above-mentioned processing unit 610, and the interface circuit 720 is used to implement the functions of the above-mentioned transceiver unit 620.

[0249] When the above communication device is a chip applied to a terminal, the terminal chip implements the functions of the terminal (i.e., the first terminal or the second terminal) in the above method embodiments. The terminal chip receives information from other modules (such as a radio frequency module or an antenna) in the terminal, and the information is sent to the terminal by a base station or other terminals; or, the terminal chip sends information to other modules (such as a radio frequency module or an antenna) in the terminal, and the information is sent by the terminal to a base station or other terminals.

[0250] It can be understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0251] The method steps in the embodiments of the present application can be implemented in a hardware manner or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in a random access memory, flash memory, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, register, hard disk, removable hard disk, CD-ROM, or any other form of storage medium well-known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC. Additionally, the ASIC can be located in a base station or a terminal. Of course, the processor and the storage medium can also exist as discrete components in a base station or a terminal.

[0252] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are executed in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, a base station, a user equipment, or other programmable devices. The computer program or instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer program or instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center in a wired or wireless manner. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center integrating one or more available media. The available medium can be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; it can also be an optical medium, such as a digital video disc; or it can be a semiconductor medium, such as a solid-state drive. The computer-readable storage medium can be a volatile or non-volatile storage medium, or can include both volatile and non-volatile types of storage media.

[0253] In various embodiments of the present application, if there is no special indication and logical conflict, the terms and / or descriptions between different embodiments are consistent and can be cross-referenced. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0254] In this application, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the relationship between associated objects and indicates that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. In the textual description of this application, the character " / " generally indicates an "or" relationship between the associated objects before and after; in the formulas of this application, the character " / " indicates a "division" relationship between the associated objects before and after.

[0255] It can be understood that the various numerical numbers involved in the embodiments of this application are only for convenience of description and are not used to limit the scope of the embodiments of this application. The magnitudes of the sequence numbers of the above processes do not mean the order of execution, and the execution order of each process should be determined by its function and internal logic.

Claims

1. A synchronization method, applied to a first terminal, characterized in that: The method comprises: Detecting synchronization information from at least one candidate synchronization reference source, wherein the first terminal is a terminal that performs synchronization based on a first synchronization type, the first synchronization type uses the terminal as a candidate synchronization reference source with the highest synchronization priority, the at least one candidate synchronization reference source includes a second terminal, the at least one candidate synchronization reference source also includes a global navigation satellite system GNSS and / or a base station, the synchronization information of the at least one candidate synchronization reference source includes first synchronization information corresponding to the second terminal, the first synchronization information includes a first synchronization signal and first indication information, the first synchronization signal is from a predefined synchronization signal set, and the first indication information indicates that the second terminal is the candidate synchronization reference source with the highest synchronization priority; Synchronize with the second terminal according to the first indication information and the first synchronization signal.

2. The method according to claim 1, characterized in that The at least one candidate synchronization reference source further includes at least one third terminal, and the synchronization information of the at least one candidate synchronization reference source further includes second synchronization information corresponding to the at least one third terminal, the second synchronization information includes a second synchronization signal and second indication information, and the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority; The method further comprises: selecting the second terminal as a synchronization source from the second terminal and the at least one third terminal according to an upper layer instruction of the first terminal; or selecting the second terminal as a synchronization source from the second terminal and the at least one third terminal according to the reference signal received power between the first terminal and the second terminal and the reference received power between the first terminal and the at least one third terminal; or If it is determined that a communication link can be successfully established between the first terminal and the second terminal, the second terminal is selected as a synchronization source from among the second terminal and the at least one third terminal.

3. The method according to claim 1, characterized in that Also includes: Stop detecting synchronization information of other candidate synchronization reference sources except the second terminal.

4. The method according to claim 3, characterized in that Also includes: When the first condition is met, synchronization information of other candidate synchronization reference sources except the second terminal is re-detected.

5. The method according to claim 1, characterized in that The at least one candidate synchronization reference source also includes at least one third terminal, the synchronization information of the at least one candidate synchronization reference source includes second synchronization information corresponding to the at least one third terminal respectively, the second synchronization information includes a second synchronization signal and second indication information, and the second indication information indicates that the third terminal is the candidate synchronization reference source with the highest synchronization priority; The method further comprises: According to the second indication information and the second synchronization signal, synchronization is performed with part or all of the at least one third terminal respectively.

6. The method according to claim 5, characterized in that Also includes: Stop detecting synchronization information of other candidate synchronization reference sources except the second terminal and part or all of the at least one third terminal.

7. The method according to claim 6, characterized in that Also includes: When the first condition is met, synchronization information of other candidate synchronization reference sources except the second terminal and part or all of the at least one third terminal is re-detected.

8. The method according to claim 4 or 7, characterized in that The first condition includes any one or more of the following: The reference signal received power between the first terminal and the second terminal is lower than a first threshold; or, The reference signal received power between the first terminal and the third terminal is lower than a first threshold; or, The upper layer of the first terminal instructs to re-search the synchronization source; or, The communication link between the first terminal and the fourth terminal fails to be established; or, The first terminal receives information from the second terminal or the third terminal instructing to re-search the synchronization source, and the information instructing to re-search the synchronization source includes the synchronization signal after the second terminal switches the synchronization source and / or the synchronization deviation before and after the second terminal switches the synchronization source, and the synchronization deviation includes time deviation and / or frequency deviation.

9. The method according to any one of claims 1 to 7, characterized in that Before synchronizing with the second terminal according to the first indication information and the first synchronization signal, the method further includes: It is determined that a reference signal received power between the first terminal and the second terminal is greater than a second threshold.

10. The method according to any one of claims 1 to 7, characterized in that After synchronizing with the second terminal according to the first indication information and the first synchronization signal, the method further includes: The third synchronization information is sent periodically, and the third synchronization information includes a third synchronization signal.

11. The method according to any one of claims 1 to 7, characterized in that The first indication information is carried in a broadcast channel.

12. A synchronization method, applied to a second terminal, characterized in that: include: generating first indication information, wherein the first indication information indicates that the second terminal is a candidate synchronization reference source with the highest synchronization priority; First synchronization information is sent periodically, where the first synchronization information includes a first synchronization signal and first indication information, and the first synchronization signal comes from a predefined synchronization signal set.

13. The method according to claim 12, characterized in that Also includes: Information indicating a re-search for a synchronization source is sent to a first terminal, wherein the information indicating a re-search for a synchronization source includes a synchronization signal after the second terminal switches the synchronization source and / or a synchronization deviation before and after the second terminal switches the synchronization source, wherein the synchronization deviation includes a time and / or frequency deviation, and the first terminal is a terminal that maintains synchronization with the second terminal.

14. The method according to claim 13, characterized in that The first terminal is a terminal that performs synchronization based on a first synchronization type, and the first synchronization type uses the terminal as a candidate synchronization reference source with the highest synchronization priority.

15. The method according to any one of claims 12 to 14, characterized in that The first indication information is carried in a broadcast channel.

16. A communication device, characterized in that: The invention comprises a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method as described in any one of claims 1 to 11 or to implement the method as described in any one of claims 12 to 15 through a logic circuit or by executing code instructions.

17. A computer-readable storage medium, characterized in that: The storage medium stores a computer program or instruction, and when the computer program or instruction is executed by a processor, the method according to any one of claims 1 to 15 is implemented.

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