Wireless ad hoc network time synchronization method, device and system and communication equipment

Abstract

The invention provides a wireless ad hoc network time synchronization method, device and system and communication equipment, and relates to the technical field of communication. The wireless ad hoc network time synchronization method comprises the following steps: generating a reference clock signal based on a GNSS (Global Navigation Satellite System) signal of a global navigation satellite system; generating a local clock signal synchronized with the reference clock signal; determining a sending window of the wireless frame according to preset sending time slot configuration; wherein the starting moment of the sending window is set to be deviated from a specified edge of the reference clock signal by a preset time delay; generating and sending the wireless frame in the sending window; wherein the wireless frame at least comprises equipment identification information and time synchronization identification information, and the initial sending time of the wireless frame is consistent with the initial time of the sending window.

Description

Technical Field

[0001] This specification relates to the field of communication technology, and in particular to a method, apparatus, system, computer program product, and computer communication equipment for time synchronization in wireless ad hoc networks. Background Technology

[0002] A wireless ad hoc network is a multi-hop wireless network that does not rely on fixed infrastructure and is autonomously composed of several mobile or fixed nodes. This type of network is widely used in military communications, emergency rescue, intelligent transportation, and the Internet of Things (IoT). Wireless mesh networks are a typical example of wireless ad hoc networks. The core characteristic of this type of network is "no central node, multi-device cooperative communication." However, because its nodes lack a unified clock source, time synchronization between nodes becomes a key technology for ensuring network coordination, time slot scheduling, positioning, and ranging functions. Traditional time synchronization methods mostly rely on message exchange between nodes within the network (such as IEEE 1588, NTP, etc.), achieving synchronization through multiple round-trip delay measurements and clock offset compensation. These methods require dedicated wireless resources for the synchronization process, and their overhead increases significantly with network size, objectively limiting the maximum number of nodes and scalability the network can support.

[0003] Therefore, some embodiments of this specification provide a time synchronization method, apparatus, system, computer program product, and computer communication device for wireless ad hoc networks with lower resource overhead and greater scalability. Summary of the Invention

[0004] This specification provides one or more embodiments of a wireless ad hoc network time synchronization method, the method comprising: generating a reference clock signal based on GNSS signals from a Global Navigation Satellite System; generating a local clock signal synchronized with the reference clock signal; determining a transmission window for a wireless frame according to a preset transmission time slot configuration; wherein the start time of the transmission window is set to be offset from a specified edge of the reference clock signal by a preset time delay; generating and transmitting a wireless frame within the transmission window; wherein the wireless frame contains at least device identification information and time synchronization identification information, and the start time of the wireless frame is consistent with the start time of the transmission window.

[0005] According to one or more embodiments of this specification, a method for generating a reference clock signal based on GNSS signals of a Global Navigation Satellite System includes: acquiring GNSS signals of a Global Navigation Satellite System; and generating a pulse signal with a preset frequency as a reference clock signal based on the GNSS signals.

[0006] The method provided according to one or more embodiments of this specification further includes: synchronizing a local clock signal based on a reference clock signal at a preset period to maintain the synchronization state between the local clock signal and the reference clock signal.

[0007] According to one or more embodiments of this specification, a method for synchronizing a local clock signal based on a reference clock signal includes: adjusting the phase and frequency of the local clock signal through a digital phase-locked loop control circuit so that a specified edge of the local clock signal is continuously aligned in time with a specified edge of the reference clock signal.

[0008] According to one or more embodiments of this specification, the specified edge is set as a fixed phase feature point in the period of the reference clock signal; the wireless frame is set to a preset duration; the preset delay is set to a non-negative integer multiple of the preset duration; and different devices in the wireless ad hoc network have preset different transmission windows within the period of the reference clock signal.

[0009] One or more embodiments of this specification also provide a time synchronization method for a wireless ad hoc network. The method includes: generating a reference clock signal based on GNSS signals from a Global Navigation Satellite System; generating a local clock signal synchronized with the reference clock signal; determining a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration; wherein the start time of the listening window is aligned with the start time of the sending window of the target communication device; receiving a radio frame from the target communication device within the listening window, and determining the receiving time of the radio frame based on the local clock signal; wherein the radio frame contains device identification information of the target communication device; comparing the receiving time with the start time of the listening window to determine a transmission delay; determining a preset feedback arrival time of the target communication device based on the device identification information contained in the radio frame; determining a sending time of a feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device; wherein the sending time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time; and sending the feedback signal to the target communication device at the sending time.

[0010] The method provided according to one or more embodiments of this specification further includes: obtaining the distance to a target communication device based on transmission delay and the propagation speed of wireless frames in a wireless ad hoc network.

[0011] According to one or more embodiments of this specification, the propagation speed of wireless signals in a wireless ad hoc network is the speed of light, or a speed of light value corrected according to current environmental parameters.

[0012] According to one or more embodiments of this specification, the feedback arrival time is earlier than the start time of the next listening window.

[0013] According to one or more embodiments of this specification, the wireless frame further includes time synchronization identification information; the method further includes: determining whether the local clock signal of the target communication device is synchronized with the reference clock signal based on the time synchronization identification information; if it is determined that they are not synchronized, initiating bidirectional message exchange to synchronize the clock with the target communication device.

[0014] According to one or more embodiments of this specification, a method for initiating bidirectional message exchange includes: determining, based on time synchronization identification information, the historical moment when the target communication device last synchronized with a reference clock signal; calculating the time interval between the received moment and the historical moment; and if the time interval is greater than a preset out-of-synchronization tolerance threshold, initiating bidirectional message exchange with the target communication device.

[0015] One or more embodiments of this specification also provide a wireless network device, comprising: a first clock module, configured to generate a reference clock signal based on GNSS signals from a Global Navigation Satellite System, and to generate a local clock signal synchronized with the reference clock signal; a transmission window determination module, configured to determine a transmission window for a wireless frame according to a preset transmission time slot configuration, wherein the start time of the transmission window is set to be offset from a specified edge of the reference clock signal by a preset time delay, and the start transmission time of the wireless frame is consistent with the start time of the transmission window; a wireless frame generation module, configured to generate a wireless frame, wherein the wireless frame includes at least device identification information and time synchronization identification information; and a first transmission module, configured to transmit the wireless frame within the transmission window.

[0016] One or more embodiments of this specification also provide a wireless network device, comprising: a second clock module, configured to generate a reference clock signal based on GNSS signals from a Global Navigation Satellite System, and generate a local clock signal synchronized with the reference clock signal; a listening window determination module, configured to determine a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration, wherein the start time of the listening window is aligned with the start time of the sending window of the target communication device; a second receiving module, configured to receive a wireless frame from the target communication device within the listening window, and determine the receiving time of the wireless frame based on the local clock signal, wherein the wireless frame contains device identification information of the target communication device; a delay determination module, configured to compare the receiving time with the start time of the listening window to determine the transmission delay; a feedback time determination module, configured to determine a preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame, and determine a transmission time of a feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device, wherein the transmission time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time; and a second sending module, configured to send the feedback signal to the target communication device at the transmission time.

[0017] One or more embodiments of this specification also provide a wireless ad hoc network time synchronization system, the system including a first terminal and a second terminal; wherein, the first terminal is used to generate a reference clock signal based on GNSS signals of a Global Navigation Satellite System; generate a local clock signal synchronized with the reference clock signal; determine a transmission window for a wireless frame according to a preset transmission time slot configuration; wherein the start time of the transmission window is set to be offset from a specified edge of the reference clock signal by a preset time delay; generate and transmit a wireless frame within the transmission window; wherein the wireless frame contains at least device identification information and time synchronization identification information, and the start time of the wireless frame is consistent with the start time of the transmission window; the second terminal is used to generate a reference clock signal based on GNSS signals of a Global Navigation Satellite System; generate a local clock signal, and synchronize the local clock signal with the reference clock signal. Signal synchronization; determining a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration; wherein the start time of the listening window is aligned with the start time of the sending window of the target communication device; receiving a wireless frame from the target communication device within the listening window, and determining the receiving time of the wireless frame based on a local clock signal; wherein the wireless frame contains device identification information of the target communication device; comparing the receiving time with the start time of the listening window to determine the transmission delay; determining a preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame; determining the sending time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device; wherein the sending time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time; sending the feedback signal to the target communication device at the sending time.

[0018] One or more embodiments of this specification also provide a computer program product, including computer instructions or a computer program, which, when executed by a processor, enables the implementation of the wireless ad hoc network time synchronization method described in some embodiments of this specification.

[0019] One or more embodiments of this specification also provide a computer communication device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it can implement the wireless ad hoc network time synchronization method described in some embodiments of this specification. Attached Figure Description

[0020] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. The same numbers in the drawings denote the same structures or steps.

[0021] Figure 1 This is a schematic diagram illustrating a time synchronization application scenario in a wireless ad hoc network, based on some embodiments of this specification.

[0022] Figure 2 This is an exemplary flowchart illustrating a time synchronization method for a wireless ad hoc network according to some embodiments of this specification.

[0023] Figure 3 This is an exemplary flowchart illustrating another wireless ad hoc network time synchronization method according to some embodiments of this specification.

[0024] Figure 4 This is an exemplary flowchart illustrating another wireless ad hoc network time synchronization method according to some embodiments of this specification.

[0025] Figure 5 This is an exemplary block diagram of a first wireless network device according to some embodiments of this specification.

[0026] Figure 6 This is an exemplary block diagram of a second wireless network device according to some embodiments of this specification. Detailed Implementation

[0027] To more clearly illustrate the technical solutions of the embodiments in this specification, the embodiments will be described in detail below with reference to the accompanying drawings. Obviously, the content described below are some examples or embodiments of this specification. For those skilled in the art, without creative effort, the technical solutions or means disclosed in this specification can be applied to other scenarios based on this technical content.

[0028] It should be understood that the terms "system," "device," "unit," and / or "module" used in this specification are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0029] Unless otherwise specified, the technical terms used to describe components, elements, etc. in this specification are not singular but may include plural. Generally speaking, terms such as "comprising" or "including" only indicate that explicitly identified steps, elements, or components are included, and these steps, elements, and components do not constitute an exclusive list, as the described method or apparatus may also include other steps or components.

[0030] This specification uses flowcharts to illustrate the operational steps performed by the apparatus or system of related embodiments. However, unless otherwise specified, the order in which these steps are described should not be construed as a limitation on the order of execution. Those skilled in the art can adjust the order of these steps based on the knowledge and information conveyed by the embodiments in this specification. Such adjustments include, but are not limited to, reversing the order of steps, merging multiple steps, and splitting a step.

[0031] A wireless ad hoc network is a distributed wireless network that does not rely on any pre-existing infrastructure. Its nodes (such as mobile devices or sensors) can autonomously discover each other, dynamically establish connections, and collaboratively forward data, forming a temporary, multi-hop communication system. Each node actively listens to its environment upon power-on, discovers neighbors by exchanging beacon messages, and negotiates routes and topology based on distributed protocols—the entire process requires no manual intervention. This type of network is suitable for scenarios without infrastructure or requiring temporary collaboration, such as military communications, emergency disaster relief, the Internet of Things (IoT), and vehicular networks. Because the nodes in this network lack a unified clock source, time synchronization between nodes becomes a key technology for ensuring network coordination, communication, time slot scheduling, positioning, and ranging functions.

[0032] GNSS (Global Navigation Satellite System) refers to all satellite systems that provide global positioning, navigation, and timing services. Examples of GNSS systems include the US GPS, China's BeiDou (BDS), Russia's GLONASS, or the European Union's Galileo. GNSS signals are radio signals transmitted by global navigation satellite systems.

[0033] In some related embodiments, wireless ad hoc networks rely on message exchange between nodes within the network (such as IEEE 1588, NTP, etc.) to achieve time synchronization through multiple round-trip delay measurements and clock skew compensation. However, this requires dedicated wireless resources for the synchronization process, and its overhead increases significantly with network size, limiting the maximum number of nodes and scalability that the wireless ad hoc network can support. In other related embodiments, the wireless ad hoc network can achieve time synchronization between nodes by independently aligning GNSS signals using the local clocks of each node in the network, but this still requires performing bidirectional ranging procedures, resulting in resource waste.

[0034] To this end, some embodiments of this specification provide a time synchronization method, apparatus, system, and computer communication device for wireless ad hoc networks. Each node in the wireless ad hoc network (including a first terminal and a second terminal) generates a reference clock signal based on GNSS signals from a Global Navigation Satellite System, and then generates a local clock signal synchronized with the reference clock signal. Further, the first terminal determines the transmission window of a wireless frame according to a preset transmission time slot configuration. The start time of the transmission window is set to be offset by a preset time delay from a specified edge of the reference clock signal. Within the transmission window, the first terminal generates and transmits a wireless frame; the start time of the wireless frame is consistent with the start time of the transmission window. Correspondingly, the second terminal determines a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration. The start time of this listening window is aligned with the start time of the target communication device's transmitting window. Within the listening window, the terminal receives radio frames from the target communication device and determines the receiving time of the radio frames based on a local clock signal. The receiving time is compared with the start time of the listening window to determine the transmission delay. Then, based on the transmission delay and the preset feedback arrival time of the target communication device, the terminal determines the transmission time of the feedback signal. This transmission time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time. By utilizing GNSS signals to provide a high-precision and stable reference clock signal, combined with a time-slotted frame transmission and reception mechanism, the second terminal can determine the transmission delay based on the difference between the receiving time and the start time of the listening window. This solves the problem of excessive radio resource consumption due to time synchronization, which limits the maximum number of nodes and scalability that a wireless ad hoc network can support.

[0035] Figure 1 This is a schematic diagram illustrating a time synchronization application scenario in a wireless ad hoc network, based on some embodiments of this specification. For example... Figure 1 As shown, in some embodiments, a wireless ad hoc network can consist of multiple node devices (e.g., Figure 1The network is composed of nodes 0 to 4. These nodes can communicate directly or via multi-hop communication, forming a flexible and dynamic network structure. In this wireless ad hoc network, each node can not only participate in data transmission as a terminal but also act as a relay node, assisting other nodes in forwarding data. Exemplarily, in some embodiments of this specification, the multiple node devices in the wireless ad hoc network can be any possible communication devices, including user terminal devices (such as smartphones, tablets, etc.), dedicated communication devices (such as vehicle-mounted / shipborne / drone-borne communication devices, portable communication boxes, etc.), IoT terminals and sensors (such as IoT cameras, environmental sensors, smart meters, or water meters, etc.). In some embodiments, the node devices in this wireless ad hoc network can be fixed or mobile. When at least one node device in the wireless ad hoc network is in a mobile state, node access or exit may occur as the node device's location changes. In this case, the current network topology can be automatically updated based on the current access status of the node device.

[0036] In some embodiments of this specification, the wireless ad hoc network time synchronization system 100 may include a first terminal 110 and a second terminal 120. The first terminal 110 and the second terminal 120, as node devices in the wireless ad hoc network, can transmit data with each other. In some embodiments, the first terminal 110 and the second terminal 120 may be the same computer communication device, which has wireless transmission and relay functions and can be deployed and run on various nodes in a distributed mesh network (wireless ad hoc network). This communication device can support access to and comply with a wireless ad hoc network protocol stack, which can be a software-hardware collaborative platform capable of supporting multi-hop routing, neighbor discovery, and dynamic topology maintenance. For example, the protocol stack may be based on standards such as IEEE 802.11s, OLSR, or AODV, and can support autonomous networking and data forwarding in various network scenarios. In some embodiments, the communication device may be a handheld communication terminal, a vehicle-mounted radio, an unmanned aerial vehicle (UAV) node, or a fixed relay station. The operator can configure the communication device as either a first terminal 110 or a second terminal 120 through its management interface, and configure the device's parameters to enable it to continuously monitor wireless signals and send and receive data frames from other nodes in the network according to preset channels, demodulation methods, and routing tables. The first terminal 110 can encapsulate, store, or prioritize data according to network conditions and service requirements, and transmit data with other communication devices (such as the second terminal 120) in the wireless ad hoc network. The second terminal 120 can verify, parse, or store received data according to network protocols and service types, and interact with other communication devices (such as the first terminal 110) in the wireless ad hoc network. In some embodiments, both the first terminal 110 and the second terminal 120 can generate a reference clock signal based on GNSS signals from the Global Navigation Satellite System, and then generate a local clock signal synchronized with the reference clock signal. The first terminal 110 can also determine the transmission window for wireless frames according to preset transmission time slot configurations, and generate and transmit wireless frames within the transmission window. The second terminal 120 can also determine a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration, receive wireless frames from the target communication device within the listening window, determine the receiving time of the wireless frame based on the local clock signal, compare the receiving time with the start time of the listening window to determine the transmission delay, determine the preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame, determine the sending time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device, and send the feedback signal to the target communication device at the sending time.

[0037] It should be noted that, Figure 1The schematic diagram illustrating a time synchronization application scenario in a wireless ad hoc network is merely an example. The time synchronization application scenario in a wireless ad hoc network described in the embodiments of this specification is intended to more clearly illustrate the technical solutions of the embodiments in this specification and does not constitute a limitation on the technical solutions provided in the embodiments of this specification. For example, Figure 1 The number of the first terminal 110 and the second terminal 120 is merely illustrative and is not intended to limit the scope of patent protection of this application. Depending on the actual situation, there can be any number of first terminals 110 and second terminals 120. In some embodiments, the first terminal 110 and the second terminal 120 can be integrated into a single communication device, which can switch operating modes to perform the functions of the first terminal 110 and / or the second terminal 120. Those skilled in the art will understand that with the development of communication technology and the emergence of new business scenarios, the technical solutions provided in the embodiments of this specification are also applicable to similar technical problems.

[0038] Figure 2 This is an exemplary flowchart illustrating a time synchronization method for a wireless ad hoc network according to some embodiments of this specification. In some embodiments, Figure 2 The illustrated process 200 can be implemented by multiple execution devices. In some embodiments, process 200 can be implemented by a wireless ad hoc network time synchronization system, for example, by... Figure 1 The wireless ad hoc network time synchronization system 100 is implemented in the example. The wireless ad hoc network time synchronization system may include a first terminal and a second terminal, for example, Figure 1 The first terminal 110 and the second terminal 120 are described. In some embodiments, the first terminal may be implemented by a first wireless network device 500 deployed on the processing device, and the second terminal may be implemented by a second wireless network device 600 deployed on the processing device. Figure 2 As shown, in some embodiments, process 200 may include the following steps.

[0039] Step 210: The first terminal and the second terminal generate reference clock signals based on the GNSS signals of the Global Navigation Satellite System, and generate their respective local clock signals synchronized with the reference clock signals.

[0040] In some embodiments, the first terminal and the second terminal can be any communication device in the wireless ad hoc network that possesses full communication capabilities (both transmitting and receiving). Depending on its role in the wireless ad hoc network, the communication device can switch between the first terminal and the second terminal. For example, the device can be a mesh device, each with transmitting and receiving capabilities. The transmitting and receiving functions of the mesh device can automatically switch according to its role as a receiver or transmitter in the wireless ad hoc network. For instance, when acting as a transmitter in the wireless ad hoc network, the mesh device switches to the role of the first terminal; while when acting as a receiver in the wireless ad hoc network, the mesh device switches to the role of the second terminal.

[0041] In some embodiments, the first and second terminals can acquire GNSS signals from global navigation satellite systems (such as GPS, BeiDou, GLONASS, etc.) through a GNSS receiving module. Based on the GNSS signal, a pulse signal with a preset frequency is generated as a reference clock signal. For example, many mesh devices themselves have a GNSS receiving module that can receive GNSS signals. Based on the time reference in the GNSS signal, a pulse signal with a preset frequency (e.g., 1 Hz, 10 Hz, etc.) is generated as a reference clock signal, providing a unified time reference for the entire network. This saves the time of bidirectional message exchange in traditional synchronization processes and avoids the cumulative errors caused by multiple forwardings in traditional synchronization processes.

[0042] In some embodiments, the first terminal and the second terminal can also synchronize their local clock signals based on a reference clock signal at preset intervals (e.g., 30 seconds, 2 minutes, etc.) to maintain the synchronization between the local clock signal and the reference clock signal. This can overcome the frequency drift (even if it is very small) of the device's local crystal oscillator, continuously correct the deviation caused by this drift, and keep the clock deviation of all communication devices in the network within a very small range, thereby ensuring the long-term stable operation of key functions such as time slot configuration and accurate ranging.

[0043] In some embodiments, the local clock signal can be used to drive various timing operations within the communication device, including wireless frame transmission and time slot switching. The first terminal and the second terminal can use a digital phase-locked loop (PLL) control circuit to adjust the phase and frequency of the local clock signal so that a specified edge of the local clock signal is continuously or substantially continuously aligned with a specified edge of the reference clock signal in time, thereby achieving synchronization between the local clock signal and the reference clock signal. For example, the reference clock signal can be a square wave, and the local clock signal, derived from the reference clock signal, can also be a square wave. Within one waveform period, by adjusting the phase and frequency of the local clock signal, the starting points of the rising or falling edges of the two square waves are aligned, thus achieving synchronization between the local clock signal and the reference clock signal.

[0044] Step 220: The first terminal determines the transmission window of the wireless frame according to the preset transmission time slot configuration, and generates and sends the wireless frame to the second terminal within the transmission window.

[0045] In some embodiments, a transmission slot is a time unit with boundaries, pre-allocated to a specific node (e.g., a first terminal) for transmitting wireless data, based on time synchronization. Within a reference clock cycle, multiple transmission slots can be divided, and each transmitting device (e.g., the first terminal) can exclusively occupy one or more transmission slots as its transmission window. In some embodiments, taking two devices A and B in a MESH network acting as the first terminal to transmit wireless frames as an example, assuming a transmission slot is 5 milliseconds, a wireless channel usage period is opened to one of devices A or B every 5 milliseconds. Transmission slot configuration can refer to configuring a set of transmission rules or parameters for the transmission window based on pre-determined transmission slots. These rules or parameters may include transmission duration, transmission window period, and transmission window allocation rules. Transmission slot configuration can be pre-set or dynamically set based on the composition of the wireless ad hoc network. For example, the logical center of the MESH network can dynamically set the transmission slot configuration for the next reference clock cycle based on broadcast information from each node device and send it to each node device, including the first terminal. The first terminal can determine the transmission window for the wireless frame based on the preset transmission slot configuration. For example, the wireless channel usage rights period corresponding to the first and second 5-millisecond intervals (e.g., 3 milliseconds) can be sequentially allocated to devices A and B. The preset transmission time slot configuration may include: transmission duration (3 milliseconds), transmission window period (every 5 milliseconds), and transmission window allocation rules (e.g., allocating the first transmission window to device A and the second transmission window to device B). The first terminal can determine its own wireless frame transmission window according to the preset transmission time slot configuration.

[0046] In some embodiments, the start time of the transmission window can be set to a preset delay offset from a specified edge of the reference clock signal. For example, the reference clock signal can be a square pulse signal with a frequency of 1Hz, and the specified edge can be the rising edge or falling edge of the square pulse. If a first terminal in the network has a preset delay of 5 milliseconds, then within each 1-second cycle, the transmission window corresponding to the second 5-millisecond interval starting from the starting point of the rising edge or falling edge of the square pulse is allocated to that first terminal. In some embodiments, the specified edge is set to a fixed phase feature point in the period of the reference clock signal. For example, the reference clock signal can be a square wave, the specified edge can be the rising edge or falling edge of the square wave, and the phase feature point can be the starting point of the rising edge or falling edge. In some embodiments, the wireless frame is set to a preset duration, and the preset delay is set to a non-negative integer multiple of the preset duration. Because the setting of the preset delay needs to take into account the time for receiving feedback, it must be longer than the frame length of the wireless frame. For example, the wireless frame (referring to the frame length of the wireless frame) can be set to a fixed millisecond or microsecond range (1 millisecond, etc.), and the preset delay can be set to 5 milliseconds. In some embodiments, different devices in a wireless ad hoc network have different preset transmission windows within the period of a reference clock signal to ensure that the transmission windows of different first terminals in the entire network are staggered.

[0047] In some embodiments, the radio frame may include device identification information and time synchronization identification information. The device identification information may be a unique identifier for each device, used to distinguish it from others. Examples include MAC address and IP address. The time synchronization identification information may be a single character or string. For example, 1 indicates synchronization with GNSS signals, and 0 indicates no synchronization with GNSS signals. Furthermore, the start time of the radio frame's transmission must be consistent with the start time of the transmission window to ensure that the transmission time of the radio frame is deterministic and predictable within the network. For example, if the start time of the transmission window is 10 milliseconds, then the start time of the radio frame's transmission is also 10 milliseconds, meaning the radio frame is transmitted precisely at 10 milliseconds.

[0048] Step 230: The second terminal determines the listening window corresponding to at least one target communication device according to the preset receiving time slot configuration, and receives wireless frames from the target communication device within the listening window.

[0049] In some embodiments, a receive time slot is similar to a transmit time slot, and is a time unit with boundaries that is pre-allocated to a specific node (e.g., a second terminal) for receiving wireless data, based on time synchronization. Within a reference clock cycle, multiple receive time slots can be divided, and each receiving device (e.g., the second terminal) can exclusively occupy one or more receive time slots as its listening window. In some embodiments, taking a MESH network with three devices A, B, and C, where devices A and B act as the first terminal transmitting wireless frames, and device C acts as the second terminal receiving wireless frames as an example, a wireless channel usage period is opened to device C every 5 milliseconds, allowing device C to transmit data with one of devices A or B. Receive time slot configuration can refer to configuring a set of listening rules or parameters for the listening window based on pre-determined receive time slots. These rules or parameters may include: listening duration, listening window period, listening window allocation rules, etc. Receive time slot configuration can be pre-set or dynamically set based on the composition of the wireless ad hoc network. For example, the logical center of the MESH network can dynamically set the receive time slot configuration based on the broadcast information of each node device in the network and send it to each node device, including the second terminal. The second terminal can determine the listening window of a wireless frame based on a preset receive time slot configuration. For example, the wireless channel usage rights time slots corresponding to the first and second 5-millisecond intervals (e.g., 3 milliseconds) can be allocated to device C. The preset receive time slot configuration may include the listening duration (3 milliseconds), the period of the listening window (once every 5 milliseconds), and the allocation rules of the listening window (e.g., allocating the first listening window to device A and the second listening window to device B). Based on the preset receive time slot configuration, the second terminal can determine the listening window corresponding to the target communication device, which may be one or more devices.

[0050] In some embodiments, the start time of the listening window can be set to be aligned with the start time of the transmission window of the target communication device. Since the local clock signals of both the second terminal and the first terminal are synchronized with the reference clock signal generated based on the GNSS signal, it is equivalent to the local clock signals of the second terminal and the first terminal being synchronized. Therefore, by controlling the preset receive time slot configuration and the preset transmit time slot configuration, the start time of the listening window and the start time of the transmission window of the target communication device can be aligned, thereby achieving a determined wireless frame transmission and reception sequence, reducing the probability of collisions, and improving network capacity. For example, within each 1-second period, the first 5 milliseconds (starting from 0 o'clock in the 1-second period) from 0 to 3 milliseconds is preset as the transmission window of the first terminal and also preset as the listening window of the second terminal. That is, within each 1-second period, the start time of the transmission window of the first terminal and the start time of the listening window of the second terminal can be aligned with 0 o'clock in the 1-second period.

[0051] Step 240: The second terminal determines whether the local clock signal of the target communication device is synchronized with the reference clock signal based on the time synchronization identifier information contained in the wireless frame.

[0052] In some embodiments, the time synchronization identifier can be a character or a string. For example, 1 can indicate that the local clock signal of the target communication device is synchronized with the reference clock signal, and 0 can indicate that the local clock signal of the target communication device is not synchronized with the reference clock signal. By identifying whether the time synchronization identifier contained in the wireless frame is 1 or 0, it is possible to quickly determine whether the local clock signal of the target communication device that sent the wireless frame is synchronized with the reference clock.

[0053] Step 250: When the second terminal determines that the local clock signal of the target communication device is synchronized with the reference clock signal, it determines the reception time of the wireless frame based on the local clock signal, and compares the reception time with the start time of the listening window to determine the transmission delay.

[0054] In some embodiments, when the second terminal detects the start delimiter (such as a physical layer preamble) of the received wireless frame, it can record the current time of its local clock signal as the reception time of the wireless frame. The wireless frame contains device identification information of the first terminal, used to identify the source of the wireless frame. For example, the device identification information identifies that the wireless frame comes from the first terminal, and the first terminal is identified as the target communication device.

[0055] In some embodiments, transmission delay can refer to the transmission time required for a signal (wireless frame) to travel from the transmitting end to the receiving end. When a signal propagates in the air, the transmission time required in both directions is generally the same, regardless of whether it travels from the first terminal to the second terminal or from the second terminal to the first terminal, as long as the distance between them remains constant. Since the local clock signals of all devices in the network (including the second terminal and the first terminal) are synchronized based on a reference clock signal generated by the GNSS signal, the local clock signals of all devices in the network can remain consistent. If the start time of the listening window and the start time of the target communication device's transmission window are also aligned, theoretically, without transmission delay, the wireless frame sent by the target communication device should arrive at the start time of the second terminal's listening window. Therefore, the difference between the actual reception time of the wireless frame sent by the target communication device received by the second terminal and the start time of the listening window can be used as the transmission delay from the second terminal to the target communication device, thus eliminating the need for multiple round-trip delay measurements between the second terminal and the first terminal to determine the transmission delay, achieving one-way transmission delay measurement. For example, within a reference clock cycle, the second terminal opens a listening window every 5 milliseconds, and this listening window is set to the first 3 milliseconds of each 5-millisecond period. This means the first listening window is from millisecond 0 to 3, the second from millisecond 5 to 8, the third from millisecond 10 to 13, and so on. Assuming the second terminal receives a radio frame at millisecond 11 (the reception time), the corresponding listening window for receiving this radio frame should be the third listening window, meaning the starting time of the listening window should be millisecond 10. Based on the reception time of the radio frame (millisecond 11) and the starting time of the listening window (millisecond 10), the transmission delay can be determined to be 1 millisecond.

[0056] In some embodiments, the second terminal can obtain the distance to the target communication device based on the transmission delay and the propagation speed of the wireless frame in the wireless ad hoc network. For example, the propagation speed of the wireless signal in the wireless ad hoc network can be the speed of light. Multiplying the speed of light by the calculated transmission delay yields the distance between the second terminal and the target communication device. Alternatively, the propagation speed of the wireless signal in the wireless ad hoc network can be a modified speed of light based on current environmental parameters. Multiplying the modified speed of light by the calculated transmission delay provides a more accurate distance between the second terminal and the target communication device.

[0057] Step 260: When the second terminal determines that the local clock signal of the target communication device is not synchronized with the reference clock signal, it initiates bidirectional message exchange, synchronizes the clock with the target communication device, and determines the transmission delay.

[0058] In some embodiments, the wireless frame from the target communication device includes time synchronization identification information, which indicates whether the local clock signal and the reference clock signal of the target communication device are synchronized. Simultaneously, the wireless frame also includes device identification information of the target communication device, which indicates which first terminal is the target communication device sending the invalid frame. Each time the second terminal receives a wireless frame, it can locally store the device identification information, time synchronization identification information, and the reception time of the wireless frame contained in the wireless frame. For example, if the second terminal receives a wireless frame (containing device identification information "A" and synchronization identification information "1") at 61 milliseconds, it associates the device identification information (A) and synchronization identification information (1) with the reception time (61 milliseconds) and stores them locally. Once the reception time is stored locally, it becomes a historical time. When the second terminal receives a radio frame containing device identification information (A) and synchronization identification information (1) at the 101st millisecond, it can update the reception time associated with it, that is, update the reception time associated with the device identification information (A) and synchronization identification information (1) to the 101st millisecond. The update can be done by data overwriting or by cumulative storage. The second terminal can determine the historical time when the target communication device was last synchronized with the reference clock signal based on the time synchronization identification information and device identification information contained in the radio frame, and calculate the time interval between the reception time of the current radio frame from the target communication device and the historical time. If the time interval is greater than the preset out-of-synchronization tolerance threshold, then bidirectional message exchange with the target communication device is initiated. The out-of-synchronization tolerance threshold is the maximum duration during which the local clock signal and the reference clock signal of the target communication device are not synchronized. For example, the second terminal receives a wireless frame at the 201st millisecond, and the wireless frame contains the device identification information "A" of device A and the synchronization identification information "0". Based on this information, it can be determined that the target communication device is device A, and the local clock signal and the reference clock signal of device A are not synchronized. At this time, the historical time stored locally by the second terminal in association with the device identification information (A) and the synchronization identification information (1) is queried. Assuming that the historical time is the 101st millisecond, the receiving time of the wireless frame (the 201st millisecond) is subtracted from the historical time (the 101st millisecond) to obtain a time interval of 100 milliseconds.

[0059] In some embodiments, since the local clock signals of each node device (including the first terminal and the second terminal) in the wireless ad hoc network can remain stable for a period of time once they have been synchronized with the reference clock signal generated based on the GNSS signal, it is not necessary to immediately initiate bidirectional message exchange for clock synchronization upon detecting a lack of synchronization. For example, if the preset out-of-synchronization tolerance threshold is 2 seconds, and the time interval (100 milliseconds) is less than the out-of-synchronization tolerance threshold (2 seconds), it is considered that the local clock signal of the target communication device and the reference clock signal are still within the synchronization range. In this case, it is not necessary to initiate bidirectional message exchange for clock synchronization, and step 270 can be executed directly. As another example, if the preset out-of-synchronization tolerance threshold is 90 milliseconds, and the time interval (100 milliseconds) is greater than the out-of-synchronization tolerance threshold (90 milliseconds), the second terminal considers that the local clock signal of the target communication device is not synchronized with the reference clock signal, and can initiate bidirectional message exchange to synchronize the clock with the target communication device and determine the transmission delay.

[0060] In some embodiments, taking the synchronization of device A (first terminal) and device B (second terminal) as an example, the process of synchronizing the clock with the target communication device through bidirectional message exchange and determining the transmission delay may include: First, device A sends a synchronization request to device B and records its sending time Send-A according to its local clock Clock-A. When device B receives this synchronization request, it also immediately records its receiving time Receipt-B according to its local clock Clock-B. At this time, device B does not yet know how much the two local clocks Clock-A and Clock-B differ. Next, device B can reply with an acknowledgment message based on its local clock Clock-B representing the receiving time, and record its sending time Send-B according to its local clock Clock-B. After receiving the acknowledgment message from device B, device A again records its arrival time Receipt-A according to its local clock Clock-A. At this point, device A has four key time points: Send-A when device A sends the synchronization request, Receipt-B when device B reports receiving the synchronization request, Send-B when device B sends its acknowledgment message, and Receipt-A when device A finally receives the acknowledgment message. By comparing these four time points, device A can analyze two key pieces of information: First, the total time it takes for the signal to travel back and forth between devices A and B. Dividing this round-trip time by two allows for the estimation of the one-way transmission delay. Second, by subtracting the impact of this transmission delay, device A can calculate whether device B's local clock Clock-B is faster or slower than its own local clock Clock-A, and by how much; this difference is the clock skew value.

[0061] Step 270: The second terminal determines the preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame.

[0062] In some embodiments, devices in a wireless ad hoc network (such as a MESH network) can operate in a half-duplex mode, meaning that a single device can only perform one of two actions at a time: receiving data or sending data. Therefore, by pre-setting a feedback arrival time for the target communication device, it can be ensured that the target communication device can receive the feedback signal, i.e., that the feedback signal sent by the second terminal arrives within the feedback reception window of the target communication device. In some embodiments, the feedback arrival time can be specified by a network protocol. For example, the network protocol can specify that each device waits to receive the feedback signal at a predetermined time (feedback arrival time) after sending a frame. The predetermined time can be based on a reference time point offset by a fixed time offset. The reference time point can be the start or end time of a transmission window determined according to a preset transmission time slot configuration. For example, the reference time point can be the start time of the transmission window (the 5th millisecond), the fixed time offset is 4 milliseconds, and the predetermined time is the 9th millisecond, which is 4 milliseconds after the 5th millisecond. After identifying the target communication device through the device identification information contained in the wireless frame, the start time of the transmission window allocated to the target communication device can be obtained according to the network protocol (see the description of step 220). Using this time as a reference time point, by shifting it backward by a fixed time offset, the preset feedback arrival time of the target communication device can be determined.

[0063] In some embodiments, the feedback arrival time can be preset to be earlier than the start time of the next listening window to avoid timing conflicts. For example, within a reference clock cycle, a receiving window appears every 5 milliseconds. The first listening window of the second terminal is from millisecond 0 to 3, the feedback arrival time is at millisecond 4, and the second listening window of the second terminal is from millisecond 5 to 8. In some embodiments, the feedback arrival time can be preset to maintain a certain interval (e.g., 1 millisecond) with the start time of the next listening window to avoid timing conflicts.

[0064] Step 280: The second terminal determines the sending time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device, and sends the feedback signal to the target communication device at the sending time.

[0065] In some embodiments, the transmission time of the feedback signal can be configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time. In some embodiments, the second terminal can determine the transmission time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device. For example, assuming the signal transmission delay between the second terminal and the target communication device is 1 millisecond within a reference clock cycle, and the preset feedback arrival time of the target communication device is the 14th millisecond, then the transmission time of the second terminal's feedback signal can be determined to be the 13th millisecond. That is, the second terminal should send the feedback signal at the 13th millisecond to ensure that it arrives at the target communication device at the 14th millisecond. Thus, the second terminal can send the feedback signal to the target communication device based on the determined transmission time. By combining one-way transmission delay measurement (comparing the reception time with the start time of the listening window) with preset feedback arrival time scheduling, low-overhead, low-latency bidirectional timing coordination of wireless ad hoc networks can be achieved.

[0066] The time synchronization method for wireless ad hoc networks is further illustrated below with a specific example. Let's take a wireless ad hoc network comprising two first terminals (device A and device B) and one second terminal (device C) as an example. In some embodiments, assuming both the transmit and receive time slots are 5 milliseconds, devices A and B sequentially transmit wireless frames to device C according to the transmit time slot. The transmit window of the first terminal and the listen window of the second terminal are both 3 milliseconds in length and their start times are aligned. The feedback window of the second terminal (used to transmit feedback signals) and the receive window of the first terminal (used to receive feedback signals) are both 2 milliseconds in length. Since the same device cannot transmit and receive data simultaneously, both devices A and B must immediately open their receive windows when the 3-millisecond transmit window ends. Therefore, the start time of device A's receive window is the 3rd millisecond to ensure that the transmission of wireless frames and the reception of feedback signals are completed within the 5-millisecond transmit time slot. Similarly, device C must open the feedback window immediately at the end of the 3-millisecond listening window in order to ensure that the wireless frame is received and the feedback signal is sent within the 5-millisecond receiving time slot, and to ensure that the feedback signal arrives at the target communication device (device A or device B) on time. Therefore, the start time of the feedback window of device C is also the 3rd millisecond.

[0067] In some embodiments, taking a wireless frame length of 1 millisecond and a feedback arrival time of 4 milliseconds after the start of the transmission window as an example, after devices A, B, and C are enabled, they respectively acquire GNSS signals from the Global Navigation Satellite System to generate a 1Hz pulse signal as a reference clock signal (i.e., one period of the reference clock signal is 1 second), and each generates a local clock signal synchronized with the reference clock signal.

[0068] In some embodiments, it is assumed that device A and device C transmit data within the first 5 milliseconds of each 1-second period. Taking device A sending a radio frame to device C at millisecond 0 as an example, this radio frame contains device identification information of device A. Device C receives a radio frame at millisecond 0.33. Based on the device identification information of device A contained in the radio frame, it determines that the target communication device is device A. Further, based on device A's preset transmission time slot configuration, the start time of device A's transmission window can be determined to be millisecond 0. Furthermore, based on the alignment of the start time of the first terminal's transmission window and the start time of the second terminal's listening window, it can be determined that the start time of device C's listening window for receiving the radio frame is also millisecond 0. Therefore, based on the reception time of the radio frame (millisecond 0.33) and the start time of its listening window (millisecond 0), the transmission delay can be determined to be 0.33 milliseconds. Based on the preset feedback arrival time (e.g., 1 millisecond earlier than the start time of the next listening window (the 5th millisecond) determined according to the preset receive time slot configuration, i.e., the 4th millisecond) and a transmission delay of 0.33 milliseconds, device C can determine that it should send a feedback signal at the 3.67th millisecond to ensure that device A receives the feedback signal at the 4th millisecond. Therefore, device C sends a feedback signal to device A at the 3.67th millisecond.

[0069] In some embodiments, taking the example of device B sending a wireless frame to device C at the 5th millisecond, the wireless frame contains device identification information of device B. Assuming device C receives a wireless frame at the 5.53rd millisecond, based on the reception time of the wireless frame (5.53rd millisecond) and the start time of its listening window (5th millisecond), the transmission delay can be determined to be 0.53 milliseconds. Furthermore, based on the device identification information of device B contained in the wireless frame, the target communication device is determined to be device B. Device C can determine, based on a preset feedback arrival time (e.g., 1 millisecond earlier than the start time of the next listening window determined according to the preset reception time slot configuration (10th millisecond, i.e., the 9th millisecond) and the 0.53 millisecond transmission delay, that it should send a feedback signal at the 8.47th millisecond to ensure that device B receives the feedback signal at the 9th millisecond. Therefore, device C sends a feedback signal to device B at the 8.47th millisecond.

[0070] By synchronizing the local clock signals of each device in the wireless ad hoc network with the reference clock signal generated based on the GNSS signal, a unified time reference can be provided for all devices in the network. Furthermore, by having each device (the first terminal) send a radio frame containing its own device identification information and time synchronization identification information at a predetermined time, a reliable time reference and identification basis can be provided for the device receiving the radio frame (the second terminal). This enables the scheduling of delay measurement and feedback signal transmission times based on unidirectional transmission, achieving low-overhead, low-latency bidirectional timing coordination.

[0071] Figure 3 This is an exemplary flowchart illustrating another time synchronization method for wireless ad hoc networks according to some embodiments of this specification. In some embodiments, Figure 3 The illustrated process 300 can be executed by a processing device, such as a first terminal 110. In some embodiments, process 300 can be implemented by a first wireless network device 500 deployed on the processing device. Figure 3 As shown, in some embodiments, process 300 may include the following steps.

[0072] Step 310: Generate a reference clock signal based on the GNSS signal of the Global Navigation Satellite System. In some embodiments, step 310 may be implemented by the first clock module 510.

[0073] In some embodiments, the GNSS signal can be a GPS, BeiDou, GLONASS, or other signal, which can be acquired by a GNSS receiving module. Based on this GNSS signal, a pulse signal with a preset frequency is generated as a reference clock signal, providing a unified time reference for the entire network. This saves time in bidirectional message exchange during traditional synchronization and avoids the accumulated errors caused by multiple forwardings during traditional synchronization. For a detailed explanation of generating the reference clock signal, please refer to the description in step 210, which will not be repeated here.

[0074] Step 320: Generate a local clock signal synchronized with the reference clock signal. In some embodiments, step 320 may be implemented by the first clock module 510.

[0075] In some embodiments, the local clock signal can be synchronized with the reference clock signal at preset intervals (e.g., 30 seconds, 2 minutes, etc.) to maintain the synchronization between the local clock signal and the reference clock signal. This ensures that the clock deviation of all communication devices in the network is always kept within a very small range, thereby ensuring the long-term stable operation of key functions such as time slot configuration and accurate ranging. In some embodiments, the phase and frequency of the local clock signal are adjusted by a digital phase-locked loop control circuit to ensure that a specified edge of the local clock signal is continuously aligned with a specified edge of the reference clock signal in time, thereby achieving synchronization between the local clock signal and the reference clock signal. For a detailed explanation of local clock signal synchronization, please refer to the description of step 210, which will not be repeated here.

[0076] Step 330: Determine the transmission window of the wireless frame according to the preset transmission time slot configuration. In some embodiments, step 330 can be implemented by the transmission window determination module 520.

[0077] In some embodiments, a transmission slot is a time unit with boundaries that is pre-allocated to a specific node for transmitting wireless data, based on time synchronization. Within a reference clock cycle, multiple transmission slots can be divided, and each device (e.g., the first terminal) can exclusively occupy one or more transmission slots as its transmission window. Transmission slot configuration can be based on pre-determined transmission slots, configuring a set of transmission rules or parameters for the transmission window. These rules or parameters may include transmission duration, transmission window period, and transmission window allocation rules. The transmission slot configuration can be preset or dynamically set based on the composition of the wireless ad hoc network. For example, the logical center of the MESH network can dynamically set the transmission slot configuration for the next reference clock cycle based on broadcast information from each node device and send it to each node device, including the first terminal. The first terminal can determine the transmission window for the wireless frame based on the preset transmission slot configuration. For a detailed explanation of the transmission window, please refer to step 220; it will not be repeated here.

[0078] In some embodiments, the start time of the transmission window can be set to a preset time delay offset from a specified edge of the reference clock signal. In some embodiments, the specified edge is set to a fixed phase feature point in the period of the reference clock signal. In some embodiments, different devices in the wireless ad hoc network have preset different transmission windows within the period of the reference clock signal to ensure that the transmission windows of different first terminals in the entire network are staggered. For a detailed explanation of setting the start time of the transmission window, please refer to the description of step 220, which will not be repeated here.

[0079] Step 340: Within the sending window, a radio frame is generated and sent. In some embodiments, step 340 can be implemented by the radio frame generation module 530, while the portion concerning sending the radio frame can be implemented by the first sending module 540.

[0080] In some embodiments, the radio frame may include device identification information and time synchronization identification information. The device identification information may be a unique identifier for each device, used to distinguish it from another device. The time synchronization identification information may be a single character or a string. Furthermore, the start time of the radio frame transmission is consistent with the start time of the transmission window, thereby ensuring that the transmission time of the radio frame is deterministic and predictable within the network. For a detailed explanation of the radio frame, please refer to the description of step 220, which will not be repeated here.

[0081] Figure 4 This is an exemplary flowchart illustrating another time synchronization method for wireless ad hoc networks according to some embodiments of this specification. In some embodiments, Figure 4The illustrated process 400 can be executed by a processing device, such as a second terminal 120. In some embodiments, process 400 can be implemented by a second wireless network device 600 deployed on the processing device. Figure 4 As shown, in some embodiments, process 400 may include the following steps.

[0082] Step 410: Generate a reference clock signal based on the GNSS signal of the Global Navigation Satellite System. In some embodiments, step 410 may be implemented by a second clock module 610.

[0083] In some embodiments, the GNSS signal can be a GPS, BeiDou, GLONASS, or other signal, which can be acquired by a GNSS receiving module. Based on this GNSS signal, a pulse signal with a preset frequency is generated as a reference clock signal, providing a unified time reference for the entire network. This saves time in bidirectional message exchange during traditional synchronization and avoids the accumulated errors caused by multiple forwardings during traditional synchronization. For a detailed explanation of generating the reference clock signal, please refer to the description of step 210, which will not be repeated here.

[0084] Step 420: Generate a local clock signal synchronized with the reference clock signal. In some embodiments, step 420 may be implemented by the second clock module 610.

[0085] In some embodiments, the local clock signal can be synchronized with the reference clock signal at a preset period (e.g., 30 seconds, 2 minutes, etc.) to maintain the synchronization between the local clock signal and the reference clock signal. This ensures that the clock deviation of all communication devices in the network is always kept within a very small range, thereby ensuring the long-term stable operation of key functions such as time slot configuration and accurate ranging. In some embodiments, the phase and frequency of the local clock signal are adjusted by a digital phase-locked loop control circuit to ensure that a specified edge of the local clock signal is continuously aligned with a specified edge of the reference clock signal in time, thereby achieving synchronization between the local clock signal and the reference clock signal. For a detailed explanation of local clock signal synchronization, please refer to the description of step 210, which will not be repeated here.

[0086] Step 430: Determine the listening window corresponding to at least one target communication device according to the preset receiving time slot configuration. In some embodiments, step 430 can be implemented by the listening window determination module 620.

[0087] In some embodiments, a receive time slot is similar to a transmit time slot and can be a time unit with boundaries that is time-synchronized, pre-allocated to a specific node (e.g., a second terminal) for receiving wireless data. Within a reference clock cycle, multiple receive time slots can be divided, and each receiving device (e.g., the second terminal) can exclusively occupy one or more receive time slots as its listening window. The receive time slot configuration can be based on a predetermined receive time slot, configuring a set of listening rules or parameters for the listening window. These rules or parameters may include, for example, listening duration, listening window period, and listening window allocation rules. The receive time slot configuration can be preset or dynamically set based on the composition of the wireless ad hoc network. For example, the logical center of the MESH network can dynamically set the receive time slot configuration based on the broadcast information of each node device in the network and send it to each node device, including the second terminal. The second terminal can determine the listening window for wireless frames based on the preset receive time slot configuration. For a detailed explanation of the preset receive time slot configuration, please refer to the description of step 230, which will not be repeated here.

[0088] In some embodiments, the start time of the listening window can be set to be aligned with the start time of the transmission window of the target communication device. This alignment can be achieved by controlling preset receive time slot configurations and preset transmit time slot configurations, thereby ensuring a defined wireless frame transmission and reception sequence, reducing the probability of collisions, and improving network capacity. For a detailed explanation of determining the listening window corresponding to the target communication device, please refer to the description of step 230, which will not be repeated here.

[0089] Step 440: Receive a wireless frame from the target communication device within the listening window, and determine the reception time of the wireless frame based on the local clock signal. In some embodiments, step 440 can be implemented by the second receiving module 630.

[0090] In some embodiments, the second terminal can listen within a defined listening window. Upon receiving a wireless frame, it can determine whether the local clock signal of the target communication device is synchronized with the reference clock signal based on the time synchronization identifier information contained in the wireless frame, thereby determining whether to initiate bidirectional message exchange for synchronization, and determining the reception time of the wireless frame based on the local clock signal. For a detailed explanation of determining whether the clock signal is synchronized, please refer to the description of step 240, which will not be repeated here.

[0091] In some embodiments, when it is determined that the local clock signal of the target communication device is out of sync with the reference clock signal, bidirectional message exchange can be initiated to synchronize the clock with the target communication device and determine the transmission delay. This ensures that a reliable and accurate time is maintained between the target communication device and the target communication device even when the local clock signal cannot be synchronized with the reference clock signal. For a detailed explanation of determining the transmission delay when the clock signals are out of sync, please refer to the description of step 260, which will not be repeated here.

[0092] In some embodiments, when it is determined that the local clock signal of the target communication device is synchronized with the reference clock signal, the reception time of the wireless frame can be determined based on the local clock signal. In some embodiments, when the start delimiter (such as a physical layer preamble) of the received wireless frame is detected, the current time of the local clock signal can be recorded as the reception time. For a detailed explanation of determining the reception time of the wireless frame, please refer to the description of step 250, which will not be repeated here.

[0093] Step 450: The receiving time is compared with the start time of the listening window to determine the transmission delay. In some embodiments, step 450 can be implemented by the delay determination module 640.

[0094] In some embodiments, transmission delay refers to the transmission time required for a signal (wireless frame) to travel from the transmitter to the receiver. Since the local clock signals of all devices in the network (including the second terminal and the first terminal) are synchronized based on a reference clock signal generated from a GNSS signal, it is equivalent to all devices in the network having consistent local clock signals. If the start time of the listening window and the start time of the target communication device's sending window are also aligned, theoretically, without transmission delay, the wireless frame sent by the target communication device should arrive at the start time of the listening window. Therefore, the difference between the actual reception time of the wireless frame sent by the target communication device and the start time of the listening window can be used as the transmission delay of the wireless frame propagating in the air, thus eliminating the need for multiple round-trip delay measurements to determine the transmission delay. In some embodiments, the second terminal can obtain the distance to the target communication device based on the transmission delay and the propagation speed of the wireless frame in the wireless ad hoc network. For a detailed explanation of determining the transmission delay, please refer to the description of step 250, which will not be repeated here.

[0095] Step 460: Determine the preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame. In some embodiments, step 460 can be implemented by the feedback time determination module 650.

[0096] In some embodiments, the wireless frame may include device identification information to identify the source of the wireless frame. The second terminal can determine the target communication device based on the device identification information contained in the wireless frame. For a detailed explanation of determining the target communication device, please refer to the description of step 270, which will not be repeated here.

[0097] In some embodiments, the feedback arrival time can be preset to be earlier than the start time of the next listening window. In some embodiments, the feedback arrival time and the start time of the next listening window can be kept at a certain interval (e.g., 1 millisecond) to avoid timing conflicts. For a detailed explanation of determining the feedback arrival time, please refer to the description of step 270, which will not be repeated here.

[0098] Step 470: Determine the transmission time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device. In some embodiments, step 470 can be implemented by the feedback time determination module 650.

[0099] In some embodiments, the transmission time of the feedback signal can be configured so that the feedback signal arrives at the target communication device at the feedback arrival time. The second terminal can determine the transmission time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device. For a detailed explanation of determining the transmission time of the feedback signal, please refer to the description of step 280, which will not be repeated here. It should be noted that steps 460 and 470 can also be implemented by two independent modules.

[0100] Step 480: At the transmission time, a feedback signal is sent to the target communication device. In some embodiments, step 480 may be implemented by the second transmission module 660.

[0101] In some embodiments, the feedback signal may include confirmation that a wireless frame has been received, so that the target communication device can determine that it has successfully completed a data transmission.

[0102] This specification also provides a wireless network device. Figure 5 This is an exemplary block diagram of a first wireless network device according to some embodiments of this specification. In some embodiments, the first wireless network device 500 may be deployed on a first terminal 110. Figure 5 As shown, in some embodiments, the first wireless network device 500 may include a first clock module 510, a transmission window determination module 520, a wireless frame generation module 530, and a first transmission module 540.

[0103] The first clock module 510 can be used to generate a reference clock signal based on GNSS signals from a global navigation satellite system, and to generate a local clock signal synchronized with the reference clock signal.

[0104] The transmission window determination module 520 can be used to determine the transmission window of the wireless frame according to the preset transmission time slot configuration. The start time of the transmission window is set to a preset time delay offset from a specified edge of the reference clock signal, and the start time of the wireless frame transmission is consistent with the start time of the transmission window.

[0105] The wireless frame generation module 530 can be used to generate wireless frames, which at least contain device identification information and time synchronization identification information.

[0106] The first transmitting module 540 can be used to transmit wireless frames within a transmitting window.

[0107] In some optional embodiments, the first clock module 510 can also be used to acquire GNSS signals from the Global Navigation Satellite System and, based on the GNSS signals, generate a pulse signal with a preset frequency as a reference clock signal.

[0108] In some optional embodiments, the first clock module 510 can also be used to synchronize the local clock signal with the reference clock signal according to a preset period, so as to maintain the synchronization state between the local clock signal and the reference clock signal.

[0109] In some alternative embodiments, the first clock module 510 can also be used to adjust the phase and frequency of the local clock signal through a digital phase-locked loop control circuit so that a specified edge of the local clock signal is continuously aligned in time with a specified edge of the reference clock signal.

[0110] In some alternative embodiments, the first wireless network device 500 may further include a first receiving module 550, which can be used to receive feedback signals.

[0111] This manual also provides another wireless network device. Figure 6 This is an exemplary block diagram of a second wireless network device according to some embodiments of this specification. In some embodiments, the second wireless network device 600 may be deployed on a second terminal 120. Figure 6 As shown, in some embodiments, the second wireless network device 600 may include a second clock module 610, a listening window determination module 620, a second receiving module 630, a delay determination module 640, a feedback time determination module 650, and a second sending module 660.

[0112] The second clock module 610 can be used to generate a reference clock signal based on GNSS signals from a global navigation satellite system, and to generate a local clock signal synchronized with the reference clock signal.

[0113] The listening window determination module 620 can be used to determine the listening window corresponding to at least one target communication device according to the preset receiving time slot configuration, and the start time of the listening window is aligned with the start time of the sending window of the target communication device.

[0114] The second receiving module 630 can be used to receive wireless frames from the target communication device within the listening window, and determine the reception time of the wireless frame based on the local clock signal. The wireless frame contains the device identification information of the target communication device.

[0115] The delay determination module 640 can be used to compare the receiving time with the start time of the listening window to determine the transmission delay.

[0116] The feedback time determination module 650 can be used to determine the preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame, and to determine the transmission time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device. The transmission time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time.

[0117] The second transmitting module 660 can be used to send a feedback signal to the target communication device at the time of transmission.

[0118] In some optional embodiments, the second clock module 610 can also be used to acquire GNSS signals from the Global Navigation Satellite System and, based on the GNSS signals, generate a pulse signal with a preset frequency as a reference clock signal.

[0119] In some optional embodiments, the second clock module 610 can also be used to synchronize the local clock signal with the reference clock signal according to a preset period, so as to maintain the synchronization state between the local clock signal and the reference clock signal.

[0120] In some optional embodiments, the second clock module 610 can also be used to adjust the phase and frequency of the local clock signal through a digital phase-locked loop control circuit so that a specified edge of the local clock signal is continuously aligned in time with a specified edge of the reference clock signal.

[0121] In some alternative embodiments, the second wireless network device 600 may further include a distance determination module 670 for obtaining the distance to the target communication device based on the transmission delay and the propagation speed of the wireless frame in the wireless ad hoc network.

[0122] In some optional embodiments, the wireless frame may also include time synchronization identification information, and the second wireless network device 600 may also include a synchronization identification module 680, used to determine whether the local clock signal of the target communication device is synchronized with the reference clock signal based on the time synchronization identification information.

[0123] In some optional embodiments, the synchronization identification module 680 can also be used to determine the historical moment when the target communication device last kept synchronized with the reference clock signal based on the time synchronization identification information, calculate the time interval between the received time and the historical time, and if the time interval is greater than a preset out-of-synchronization tolerance threshold, it is determined to be out of sync.

[0124] In some optional embodiments, the second wireless network device 600 may further include a synchronization restart module 690, used to initiate bidirectional message exchange with the target communication device when the local clock signal of the target communication device is not synchronized with the reference clock signal.

[0125] This specification also provides a time synchronization system for wireless ad hoc networks. In some embodiments, the wireless ad hoc network time synchronization system may include a first terminal and a second terminal. Figure 1 As shown, in some embodiments, the wireless ad hoc network time synchronization system 100 may include a first terminal 110 and a second terminal 120.

[0126] In some embodiments, the first terminal can be used to generate a reference clock signal based on the GNSS signal of the Global Navigation Satellite System, generate a local clock signal synchronized with the reference clock signal, determine the transmission window of the radio frame according to a preset transmission time slot configuration, wherein the start time of the transmission window is set to be offset by a preset time delay from a specified edge of the reference clock signal, and generate and transmit a radio frame within the transmission window, wherein the radio frame contains at least device identification information and time synchronization identification information, and the start time of the radio frame is consistent with the start time of the transmission window.

[0127] In some embodiments, the second terminal can be used to generate a reference clock signal based on GNSS signals from a Global Navigation Satellite System, generate a local clock signal, and synchronize the local clock signal with the reference clock signal. According to a preset receive time slot configuration, a listening window corresponding to at least one target communication device is determined, wherein the start time of the listening window is aligned with the start time of the target communication device's transmit window. Within the listening window, radio frames from the target communication device are received, and the reception time of the radio frames is determined based on the local clock signal. The radio frames contain device identification information of the target communication device. The reception time is compared with the start time of the listening window to determine the transmission delay. Based on the device identification information contained in the radio frames, a preset feedback arrival time of the target communication device is determined. Based on the transmission delay and the preset feedback arrival time of the target communication device, a transmission time of the feedback signal is determined, wherein the transmission time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time. At the transmission time, the feedback signal is transmitted to the target communication device.

[0128] For more information on each module, please refer to [link / reference]. Figure 2-6 The relevant explanations will not be repeated here. It should be understood that... Figure 2-6 The systems and modules shown can be implemented in various ways. For example, in some embodiments, the systems and modules can be implemented by hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the methods and systems described above can be implemented using computer-executable instructions and / or included in the control code of a processor, such as on a media such as a disk, CD, or DVD-ROM, or in the memory of a programmable device. The systems and modules of this specification can be implemented not only by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips and transistors, or programmable hardware devices such as field-programmable gate arrays and programmable logic devices, but also by software, for example, executed by various types of processors, or by a combination of the aforementioned hardware circuits and software (e.g., firmware).

[0129] It should be noted that the above description of the system and its modules is for convenience only and should not be construed as limiting this specification to the embodiments described. It is understood that those skilled in the art, after understanding the principles of this system, may arbitrarily combine the various modules without departing from these principles to form subsystems connected to other modules. Alternatively, some modules may be split to obtain more modules or multiple units under a single module. Such modifications are all within the scope of this specification.

[0130] Some embodiments of this specification also provide a computer program product, including a computer program that, when at least a portion of the computer program is executed by a processor, can perform the functions outlined in the appendix to this specification. Figures 2-4 The method is illustrated. In some embodiments, the computer program product may involve only a computer program, which may be carried on a storage medium or a processing device. In other embodiments, the computer program product may also be a storage medium or a processing device containing the aforementioned computer program. The processing device may include one or more processors, and the storage medium.

[0131] In some embodiments, the processor may be a combination of one or more of the following processors: central processing unit (CPU), application-specific integrated circuit (ASIC), application-specific instruction set processor (ASIP), graphics processing unit (GPU), physical processing unit (PPU), digital signal processor (DSP), field-programmable gate array (FPGA), programmable logic device (PLD), programmable logic controller (PLC), reduced instruction set computer (RISC), and microprocessor.

[0132] In some embodiments, the storage medium may include one or more combinations of the following: mass storage, removable storage, volatile read / write memory, and read-only memory (ROM). Exemplary mass storage may include disks, optical disks, solid-state drives, etc. Exemplary removable storage may include flash drives, floppy disks, optical disks, memory cards, compressed hard drives, magnetic tapes, etc. Exemplary volatile read / write memory may include random access memory (RAM). Exemplary RAM may include dynamic random access memory (DRAM), dual data rate synchronous dynamic random access memory (DDRSDRAM), static random access memory (SRAM), and silicon controlled retrieval memory (SCR). RAM and zero-capacitance memory (Z-RAM) RAM, etc. Exemplary read-only memories may include masked read-only memories (MROM), programmable read-only memories (PROM), erasable programmable read-only memories (EPROM), electrically erasable programmable read-only memories (EEPROM), and compressed hard disk read-only memories (CD-ROM). ROM and multi-functional hard disk read-only memory, etc.

[0133] The beneficial effects that the embodiments of this specification may bring include, but are not limited to: all devices in the wireless ad hoc network synchronize their local clock signals based on a unified reference clock signal generated by GNSS signals, saving the time of bidirectional message exchange in the traditional synchronization process and avoiding the cumulative errors caused by multiple forwardings in the traditional synchronization process; by aligning the start time of the listening window with the start time of the target communication device's sending window, deterministic wireless frame transmission and reception timing is achieved, reducing the probability of collisions and improving network capacity; based on one-way transmission delay measurement (comparing the receiving time with the start time of the listening window) and preset feedback arrival time scheduling, low-overhead, low-latency bidirectional timing coordination of the wireless ad hoc network is achieved; combined with time synchronization identification information and a loss-of-synchronization detection mechanism, traditional synchronization operations (bidirectional message exchange) can be quickly triggered when some nodes (first terminal) lose synchronization, enhancing network robustness. It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may occur can be any one or a combination of the above, or any other possible beneficial effects.

[0134] The basic concepts have been described above. It is obvious that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to this specification by those skilled in the art. Such modifications, improvements, and corrections are taught in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

Claims

1. A time synchronization method for a wireless ad hoc network, characterized in that, The method includes: Generate a reference clock signal based on GNSS signals from the Global Navigation Satellite System; Generate a local clock signal synchronized with the reference clock signal; The transmission window of the wireless frame is determined according to the preset transmission time slot configuration; wherein the start time of the transmission window is set to be offset by a preset time delay from a specified edge of the reference clock signal; Within the transmission window, the wireless frame is generated and transmitted; wherein the wireless frame contains at least device identification information and time synchronization identification information, and the start time of the wireless frame transmission is consistent with the start time of the transmission window.

2. The method according to claim 1, characterized in that, The generation of the reference clock signal based on the GNSS signal of the Global Navigation Satellite System includes: Acquire GNSS signals from the Global Navigation Satellite System; Based on the GNSS signal, a pulse signal with a preset frequency is generated as a reference clock signal.

3. The method according to claim 1, characterized in that, The method further includes: synchronizing the local clock signal based on the reference clock signal at a preset period to maintain the synchronization between the local clock signal and the reference clock signal.

4. The method according to claim 3, characterized in that, The synchronization of the local clock signal based on the reference clock signal includes: The phase and frequency of the local clock signal are adjusted by a digital phase-locked loop control circuit so that the specified edge of the local clock signal is continuously aligned with the specified edge of the reference clock signal in time.

5. The method according to any one of claims 1-4, characterized in that, The specified edge is set as a fixed phase feature point in the period of the reference clock signal; The wireless frame is set to a preset duration; the preset delay is set to a non-negative integer multiple of the preset duration; Within the period of the reference clock signal, different devices in the wireless ad hoc network have different preset transmission windows.

6. A time synchronization method for a wireless ad hoc network, characterized in that, The method includes: Generate a reference clock signal based on GNSS signals from the Global Navigation Satellite System; Generate a local clock signal synchronized with the reference clock signal; Based on a preset receive time slot configuration, a listening window corresponding to at least one target communication device is determined; wherein the start time of the listening window is aligned with the start time of the send window of the target communication device. Within the listening window, a wireless frame from the target communication device is received, and the reception time of the wireless frame is determined based on the local clock signal; wherein, the wireless frame contains the device identification information of the target communication device; The receiving time is compared with the start time of the listening window to determine the transmission delay; Based on the device identification information contained in the wireless frame, the preset feedback arrival time of the target communication device is determined; Based on the transmission delay and the preset feedback arrival time of the target communication device, the transmission time of the feedback signal is determined; wherein, the transmission time is configured such that the feedback signal arrives at the target communication device at the feedback arrival time; At the specified transmission time, the feedback signal is sent to the target communication device.

7. The method according to claim 6, characterized in that, The method further includes: The distance to the target communication device is obtained based on the transmission delay and the propagation speed of the wireless frame in the wireless ad hoc network.

8. The method according to claim 7, characterized in that, The propagation speed of the wireless signal in the wireless ad hoc network is the speed of light, or the speed of light corrected according to the current environmental parameters.

9. The method according to claim 7, characterized in that, The feedback arrives earlier than the start time of the next listening window.

10. The method according to claim 7, characterized in that, The wireless frame also includes time synchronization identification information; the method further includes: Based on the time synchronization identifier information, it is determined whether the local clock signal of the target communication device is synchronized with the reference clock signal; If it is determined that the communication is out of sync, then bidirectional message exchange is initiated to synchronize the clock with the target communication device.

11. The method according to claim 10, characterized in that, The initiation of bidirectional message exchange includes: Based on the time synchronization identifier information, determine the historical moment when the target communication device last synchronized with the reference clock signal; Calculate the time interval between the received time and the historical time; If the time interval is greater than the preset out-of-step tolerance threshold, then bidirectional message exchange with the target communication device is initiated.

12. A wireless network device, characterized in that, include: The first clock module is used to generate a reference clock signal based on the GNSS signal of the Global Navigation Satellite System, and to generate a local clock signal synchronized with the reference clock signal; The transmission window determination module is used to determine the transmission window of the wireless frame according to the preset transmission time slot configuration. The start time of the transmission window is set to be offset by a preset time delay from a specified edge of the reference clock signal, and the start time of the wireless frame is consistent with the start time of the transmission window. A wireless frame generation module is used to generate the wireless frame, wherein the wireless frame contains at least device identification information and time synchronization identification information; The first transmitting module is used to transmit the wireless frame within the transmitting window.

13. A wireless network device, characterized in that, include: The second clock module is used to generate a reference clock signal based on the GNSS signal of the Global Navigation Satellite System, and to generate a local clock signal synchronized with the reference clock signal. The listening window determination module is used to determine a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration, wherein the start time of the listening window is aligned with the start time of the sending window of the target communication device. The second receiving module is configured to receive wireless frames from the target communication device within the listening window, and determine the reception time of the wireless frame based on the local clock signal. The wireless frame contains device identification information of the target communication device. The delay determination module is used to compare the receiving time with the start time of the listening window to determine the transmission delay; The feedback time determination module is used to determine the preset feedback arrival time of the target communication device based on the device identification information contained in the wireless frame, and to determine the transmission time of the feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device. The transmission time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time. The second transmitting module is used to transmit the feedback signal to the target communication device at the transmitting time.

14. A time synchronization system for a wireless ad hoc network, characterized in that, The system includes a first terminal and a second terminal; The first terminal is used to generate a reference clock signal based on GNSS signals from the Global Navigation Satellite System; and to generate a local clock signal synchronized with the reference clock signal. According to the preset transmission time slot configuration, the transmission window of the wireless frame is determined; wherein, the start time of the transmission window is set to be offset by a preset time delay from a specified edge of the reference clock signal; within the transmission window, the wireless frame is generated and transmitted; wherein, the wireless frame contains at least device identification information and time synchronization identification information, and the start time of the wireless frame is consistent with the start time of the transmission window; The second terminal is configured to: generate a reference clock signal based on GNSS signals from a Global Navigation Satellite System; generate a local clock signal and synchronize the local clock signal with the reference clock signal; determine a listening window corresponding to at least one target communication device according to a preset receiving time slot configuration; wherein the start time of the listening window is aligned with the start time of the sending window of the target communication device; receive a radio frame from the target communication device within the listening window and determine the receiving time of the radio frame based on the local clock signal; wherein the radio frame contains device identification information of the target communication device; compare the receiving time with the start time of the listening window to determine a transmission delay; determine a preset feedback arrival time of the target communication device based on the device identification information contained in the radio frame; determine a sending time of a feedback signal based on the transmission delay and the preset feedback arrival time of the target communication device; wherein the sending time is configured to ensure that the feedback signal arrives at the target communication device at the feedback arrival time; and send the feedback signal to the target communication device at the sending time.

15. A computer program product, characterized in that, It includes computer instructions or computer programs, which, when executed by a processor in at least a portion, enable the implementation of the wireless ad hoc network time synchronization method as described in any one of claims 1 to 11.

16. A computer communication device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it is able to implement the wireless ad hoc network time synchronization method as described in any one of claims 1 to 11.

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