Wireless Mesh network-oriented high-robustness PTP time synchronization method and system

Abstract

The invention relates to the technical field of wireless communication networks, and particularly discloses a high-robustness PTP time synchronization method and system for a wireless Mesh network. According to the method, global topology information and real-time link quality information of a wireless Mesh network are obtained through a centralized network controller, an optimal end-to-end synchronization path is dynamically calculated for a slave clock node, an intermediate node on the path performs residence time accumulation correction in a transparent clock mode, high-precision end-to-end synchronization of a slave clock and a master clock is realized, and the synchronization precision of the slave clock and the master clock is improved. And the synchronization stability is ensured through continuous monitoring and seamless switching of a backup path. The system comprises a centralized network controller, a PTP master clock and a plurality of enhanced Mesh nodes. According to the method, the problems of poor dynamic topology adaptation, large transmission delay jitter, multi-hop error accumulation and the like of a standard PTP protocol in a wireless Mesh network are solved, the synchronization precision and robustness are remarkably improved, and a core support is provided for deterministic scheduling of a wireless TSN network.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication networks, in particular to a high-robustness PTP time synchronization method and system for a wireless Mesh network. BACKGROUND

[0002] As a core technology for realizing real-time communication in key fields such as industrial automation and smart grid, Time-Sensitive Networking (TSN) requires that each node in the network maintains microsecond-level or even nanosecond-level time synchronization, which is a prerequisite for realizing time-aware shaping, traffic scheduling and other deterministic transmission technologies. IEEE 1588 Precision Time Protocol (PTP) has become the core protocol for clock synchronization in the TSN system due to its high-precision synchronization performance.

[0003] In a wired network environment, the link transmission delay is fixed and predictable, and the PTP protocol can achieve extremely high synchronization accuracy through delay measurement and compensation mechanisms. However, as a distributed wireless communication network, wireless Mesh networks have characteristics such as node mobility, dynamic link changes, and channel sharing, and directly applying the standard PTP protocol faces many serious challenges: First, the dynamic topology and path uncertainty problem is prominent. The nodes in the wireless Mesh network may move with the change of the application scenario, and the link quality is affected by environmental interference, signal attenuation and other factors, showing dynamic fluctuations. The Best Master Clock (BMC) algorithm used by the standard PTP protocol is a distributed election mechanism, which selects the master clock path based only on local network information, and it is difficult to obtain a global optimal solution. And this algorithm is slow to react, when the network topology changes, it cannot quickly adjust the synchronization path, leading to a dramatic fluctuation in synchronization accuracy or even synchronization interruption, frequent switching of the master clock path or long-term suboptimal state.

[0004] Second, the shared medium introduces transmission delay uncertainty. The wireless channel is a shared transmission medium, and when multiple nodes send data at the same time, channel conflicts will occur, which need to be solved through backoff and retransmission mechanisms, which makes the transmission delay of PTP messages have great randomness and jitter. The delay request-response mechanism of the standard PTP protocol can only compensate for the fixed delay component, and cannot effectively eliminate the synchronization error caused by this random jitter, seriously damaging the synchronization accuracy.

[0005] Third, the multi-hop error accumulation problem is significant. In a multi-hop wireless Mesh network, traditional PTP synchronization uses hop-by-hop boundary clocks or peer-to-peer delay mechanisms, each hop introduces a certain synchronization error, and these errors will accumulate from the master clock, causing the synchronization deviation between the edge node and the master clock to increase continuously, which cannot meet the high-precision synchronization requirements of TSN services.

[0006] In summary, the prior art lacks a PTP time synchronization scheme that can comprehensively solve the problems of dynamic topology adaptation, transmission delay jitter suppression and multi-hop error accumulation in a global perspective, making it difficult to effectively guarantee synchronization accuracy and stability in a dynamic and multi-hop wireless Mesh network environment, and limiting the application and promotion of TSN technology in wireless scenarios. Therefore, it is of great practical significance and application value to develop a high-robustness PTP time synchronization method and system for wireless Mesh networks. SUMMARY

[0007] The purpose of the present application is to overcome the low synchronization accuracy, poor robustness and difficulty in adapting to dynamic topology of the standard PTP protocol in the application of wireless Mesh networks in the prior art, and to provide a high-robustness PTP time synchronization method and system for wireless Mesh networks, which can establish and maintain a high-precision and high-robustness global time reference for TSN services in an unstable wireless Mesh network environment, and solve key problems such as dynamic topology adaptation, transmission delay jitter and multi-hop error accumulation.

[0008] To solve the above technical problems, the embodiments of the present application provide the following technical solutions: a high-robustness PTP time synchronization method for wireless Mesh networks, comprising the following steps: Step S1: The centralized network controller obtains the global topology information and real-time link quality information of the wireless Mesh network; Step S2: Based on the global topology information and real-time link quality information, a end-to-end synchronization path leading to the PTP master clock is dynamically calculated for each slave clock node in the network, and the calculation criteria include one or more of path stability, minimum hop count and load balancing; Step S3: The configuration information of the end-to-end synchronization path is sent to the related Mesh nodes on the path, and the Mesh nodes interact with the designated upstream nodes according to the configuration information and PTP packets, the intermediate nodes in the path work in transparent clock mode, and the PTP packets are corrected by residence time accumulation, so that the slave clock nodes realize end-to-end time synchronization with the master clock based on the corrected packets; Step S4: The centralized network controller continuously monitors the performance of the synchronization path, and triggers seamless switching from the primary synchronization path to the backup synchronization path when the path quality is lower than the preset threshold.

[0009] Further, in step S1, the global topology information is obtained through the registration information and neighbor list collected after the Mesh nodes are online, and the real-time link quality information includes at least one of the signal-to-noise ratio, transmission delay, jitter, packet loss rate and hop count of the link, which is periodically reported by the enhanced Mesh node to the centralized network controller.

[0010] Further, in step S2, the path stability is determined according to the link historical quality fluctuation amplitude, and the link with a fluctuation amplitude less than a preset fluctuation threshold is preferentially selected to form a synchronization path; the hop number minimization is to make the hop number of the synchronization path not exceed a preset maximum hop number threshold under the premise of meeting the path stability requirement; and the load balancing is to disperse the synchronization traffic to avoid the PTP message processing load of a single relay node exceeding a maximum load threshold.

[0011] Further, in step S3, the configuration information includes an upstream master clock designation instruction, a transparent clock working mode configuration instruction, and an initial path delay compensation value, and after the enhanced Mesh node receives the configuration information, the proxy module is used to parse and execute the instructions to establish a PTP communication link with a designated upstream node.

[0012] Further, in step S3, the residence time accumulation correction in the transparent clock mode is specifically that after the intermediate node receives a PTP message, a first time stamp when the message enters the node and a second time stamp when the message leaves the node are recorded, a time difference between the two is calculated as the residence time, and the residence time is written into a reserved field of the PTP message to realize accumulation of the residence time.

[0013] Further, in step S4, the synchronization path performance monitoring includes real-time detection of a signal-to-noise ratio, a transmission delay, a jitter, and a packet loss rate of a link, and the preset threshold includes a minimum signal-to-noise ratio threshold, a maximum delay threshold, a maximum jitter threshold, and a maximum packet loss rate threshold, and when any parameter exceeds the corresponding threshold and the duration reaches a preset length of time, it is determined that the path quality is lower than the threshold.

[0014] Further, in step S4, the backup synchronization path is generated by the centralized network controller when the main synchronization path is calculated, the link overlap rate of the backup path and the main synchronization path does not exceed a preset overlap threshold, and the response time of seamless switching does not exceed 10 milliseconds.

[0015] The application further provides a high-robustness PTP time synchronization system for a wireless Mesh network, which is used to implement the above method and includes the following components. A centralized network controller is configured to maintain global topology information and real-time link quality information of the wireless Mesh network, dynamically calculate an end-to-end synchronization path, and issue configuration information, continuously monitor the performance of the synchronization path, and trigger path switching. A PTP master clock is configured to provide a standard time signal as a time reference of the network. A plurality of enhanced Mesh nodes are configured to communicate with the centralized network controller, and each enhanced Mesh node includes a proxy module configured to receive and execute the configuration instructions of the controller, report local link state information, and process PTP messages in a transparent clock mode.

[0016] Further, the centralized network controller comprises a topology maintenance module, a link quality monitoring module, a path calculation module, a configuration issuing module and a path switching module, the topology maintenance module is used for constructing a dynamic network map, the link quality monitoring module is used for receiving and analyzing link parameters reported by Mesh nodes in real time, the path calculation module is used for executing a dynamic path optimization algorithm, the configuration issuing module is used for sending configuration instructions to Mesh nodes, and the path switching module is used for triggering and executing a path switching process.

[0017] Further, the proxy module of the enhanced Mesh node comprises an instruction receiving unit, a state reporting unit and a message processing unit, the instruction receiving unit is used for receiving configuration instructions issued by the controller, the state reporting unit is used for periodically reporting local link states, and the message processing unit is used for processing PTP messages in a transparent clock mode, including timestamp recording, residence time calculation and message forwarding.

[0018] The beneficial effects of the above technical solutions of the present application are as follows: 1. The centralized network controller selects the optimal stable path, avoids the local optimal problem of the distributed BMC algorithm, reduces the influence of path fluctuation on synchronization accuracy. At the same time, the end-to-end transparent clock mechanism is adopted, the residence time of PTP messages is accurately measured and cumulatively corrected by the intermediate node, the total transmission delay of the clock node can be directly calculated from the master clock, the multi-hop error accumulation is effectively suppressed, the synchronization error caused by wireless channel jitter and multi-hop transmission is significantly reduced, the synchronization accuracy can reach the microsecond level, and the strict requirements of TSN service are met.

[0019] 2. The centralized network controller continuously monitors the network topology and link quality, can quickly perceive the topology changes such as node movement and link failure. By pre-calculating the backup synchronization path, millisecond-level seamless switching can be realized when the main path quality deteriorates, avoiding synchronization interruption, and greatly enhancing the reliability of the system in the dynamic wireless Mesh network environment.

[0020] 3. The centralized network controller has a global network view, can optimize the synchronization path from the perspective of the entire network, disperses the synchronization traffic through load balancing criteria, avoids overloading of a single relay node, and improves the synchronization efficiency and stability of the entire network.

[0021] 4. The high-precision and high-robustness global time reference provided by the application is a prerequisite for deploying key TSN technologies such as time-aware shaping and traffic scheduling in a wireless Mesh network. By solving the clock synchronization problem in a wireless environment, the application breaks the application bottleneck of TSN technology in a wireless scenario, promotes the development of wireless deterministic networks, and can be widely applied in industrial Internet of Things, intelligent transportation, remote medical care, smart power grids and other fields, and has important industrial value.

[0022] 5. The application is designed based on the IEEE1588 PTP protocol standard and has good compatibility with existing wired TSN networks, and can realize seamless connection of wireless Mesh networks and wired TSN networks. The proxy module of the enhanced Mesh node can be realized on the existing Mesh node through software upgrading, without the need for large-scale replacement of hardware devices, thereby reducing the deployment and upgrading costs. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 a flow chart of the high-robustness PTP time synchronization method for a wireless Mesh network of the application; Figure 2 a block diagram of the centralized network controller of the high-robustness PTP time synchronization system for a wireless Mesh network of the application; Figure 3 a block diagram of the enhanced Mesh node of the high-robustness PTP time synchronization system for a wireless Mesh network of the application; Figure 4 a schematic diagram of the overall architecture of the system of the application; Figure 5 a flow chart of the dynamic synchronization path switching of the application. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and advantages of the application more clear, the following will be described in detail with reference to the drawings and specific embodiments.

[0025] As shown in Figure 1 , the application proposes a high-robustness PTP time synchronization method for a wireless Mesh network, including the following steps: Step S1: The centralized network controller obtains the global topology information and real-time link quality information of the wireless Mesh network; Step S2: Based on the global topology information and real-time link quality information, an end-to-end synchronization path leading to a PTP master clock is dynamically calculated for each slave clock node in the network, and the calculation criteria include one or more of path stability, minimum hop count and load balancing; Step S3: configuration information of the end-to-end synchronization path is issued to relevant Mesh nodes on the path, the Mesh nodes interact with the specified upstream node according to the configuration information, the intermediate nodes in the path work in a transparent clock mode, and the PTP message is corrected based on the residence time accumulation, so that the slave clock node realizes end-to-end time synchronization with the master clock based on the corrected message; Step S4: the centralized network controller continuously monitors the performance of the synchronization path, and triggers seamless switching from the master synchronization path to the backup synchronization path when the path quality is lower than the preset threshold.

[0026] The method realizes high-precision and high-robustness time synchronization of each node in the wireless Mesh network in a combination of centralized control and end-to-end synchronization, and specifically includes the following steps: Network discovery and topology construction (step S1) The centralized network controller establishes a communication connection with all enhanced Mesh nodes in the wireless Mesh network through a network discovery protocol. After the enhanced Mesh node is online, the enhanced Mesh node automatically sends registration information to the centralized network controller, including a node identifier, hardware parameters and an initial neighbor list. After the controller receives the registration information, the controller constructs an initial network topology structure, and continuously receives local link state information periodically reported by each enhanced Mesh node. The link state information includes key parameters such as signal-to-noise ratio, transmission delay, jitter, packet loss rate and hop count of the link. Based on the real-time data, the controller dynamically updates the network topology map to form a global and real-time network view.

[0027] Dynamic optimal synchronization path calculation (step S2) The centralized network controller dynamically calculates an end-to-end synchronization path to the PTP master clock for each slave clock node (i.e., an enhanced Mesh node that needs to be synchronized with the master clock) in the network based on the maintained global topology information and real-time link quality information. The path calculation adopts multi-objective optimization criteria, specifically including: Path stability priority: by analyzing the historical quality data of the link, the fluctuation amplitude of the link quality is calculated, and the link with a fluctuation amplitude less than a preset fluctuation threshold is preferentially selected to ensure the stability of the synchronization path; Minimum hop count: under the premise of meeting the path stability requirement, a path with fewer hops is preferentially selected to reduce the error accumulation caused by multiple hops, and the hop count of the synchronization path is not more than a preset maximum hop count threshold; Load balancing: the PTP message processing load of each relay node is monitored in real time, and the synchronization traffic is dispersed to avoid the load of a single relay node exceeding the maximum load threshold, and to prevent the node from becoming a network bottleneck.

[0028] Meanwhile, the controller pre-computes at least one backup synchronization path for each main synchronization path, the backup path has a link overlap rate with the main synchronization path not exceeding a preset overlap threshold, ensuring that the backup path can be quickly switched when the main path fails.

[0029] Configuration and activation of the synchronization path (step S3) The centralized network controller converts the calculated end-to-end synchronization path into specific configuration information and sends the configuration information to the related enhanced Mesh nodes on the path through a secure communication channel. The configuration information includes upstream master clock designation instructions (which explicitly specify the synchronization upstream node of each node), transparent clock operation mode configuration instructions, and initial path delay compensation values. The enhanced Mesh nodes receive the configuration information through the built-in proxy module, parse and execute the instructions, establish a PTP communication link with the specified upstream node, and complete the activation of the synchronization path.

[0030] End-to-end synchronization and delay correction (step S3 continued) After the activation of the synchronization path, the enhanced Mesh nodes interact with the specified upstream node according to the configuration information. The intermediate nodes in the path (i.e., the enhanced Mesh nodes between the master clock and the slave clock) work in transparent clock mode, and the specific processing flow is as follows: After receiving the PTP packet sent by the upstream node, the intermediate node immediately records the first timestamp of the packet entering the node (based on the local clock of the node); After the node processes the PTP packet as necessary (such as verification and caching), it records the second timestamp of the packet leaving the node; Calculate the difference between the first timestamp and the second timestamp to obtain the residence time of the PTP packet at the node; Write the calculated residence time into the reserved field of the PTP packet to accumulate the residence time; The intermediate node forwards the PTP packet carrying the accumulated residence time to the downstream node until the packet reaches the slave clock node.

[0031] After receiving the PTP packet, the slave clock node extracts the master clock timestamp, accumulated residence time, and transmission delay related information from the packet, combines the local clock data, accurately calculates the time deviation from the master clock, and corrects the local clock based on the deviation, achieving end-to-end time synchronization with the master clock, rather than traditional hop-by-hop synchronization.

[0032] Continuous monitoring and seamless switching (step S4) The centralized network controller continuously monitors the performance of the activated synchronization path, detects the signal-to-noise ratio, transmission delay, jitter, and packet loss rate of each link in real time, and compares them with the preset thresholds (including the minimum signal-to-noise ratio threshold, the maximum delay threshold, the maximum jitter threshold, and the maximum packet loss rate threshold). When any performance parameter of a synchronization path exceeds the corresponding threshold and the duration reaches the preset length of time, the controller determines that the quality of the path is lower than the threshold, and immediately triggers the path switching process: The controller selects the optimal backup synchronization path from the pre-computed backup path library; The configuration update instruction for quickly generating the backup path is issued to the affected enhanced Mesh nodes; After receiving the instruction, the enhanced Mesh nodes quickly switch to the backup synchronization path and continue to maintain synchronization with the master clock.

[0033] The response time of the entire switching process is not more than 10 milliseconds, realizing seamless connection of synchronization and avoiding synchronization interruption.

[0034] (2) High-robustness PTP time synchronization system for wireless Mesh network As shown in Figure 2 , the system is designed to implement the above method and includes a centralized network controller 1, a PTP master clock 2, and multiple enhanced Mesh nodes 3. Each component works cooperatively to ensure high-precision and high-robustness time synchronization for the wireless Mesh network.

[0035] The centralized network controller 1, as the core control unit of the system, has global network management and scheduling capabilities, including the following functional modules: Topology maintenance module 11: responsible for receiving the registration information and neighbor list of enhanced Mesh nodes, building and dynamically updating the global network topology map; Link quality monitoring module 12: receives real-time link state information reported by each enhanced Mesh node, analyzes and stores parameters such as signal-to-noise ratio, delay, jitter, and packet loss rate, and generates a link quality evaluation report; Path calculation module 13: based on the data provided by the topology maintenance module and the link quality monitoring module, runs a dynamic path optimization algorithm to calculate the primary synchronization path and the backup synchronization path for each slave clock node; Configuration delivery module 14: delivers the configuration information generated by the path calculation module (including upstream node designation, working mode configuration, delay compensation value, etc.) to the enhanced Mesh nodes through a secure channel, and ensures accurate transmission and execution of the configuration instruction; Path switching module 15: continuously monitor the synchronization path performance, when detecting that the path quality is not up to standard, trigger the path switching process, issue backup path configuration instructions, coordinate the enhanced Mesh node to complete seamless switching.

[0036] The centralized network controller can be implemented based on a software-defined network (SDN) architecture, and has flexible expansion and rapid deployment capabilities.

[0037] The PTP master clock 2, as the time reference of the network, is usually deployed in the root node or gateway node connected to the wired TSN network, and uses a high-precision clock source (such as a GPS clock, an atomic clock) to provide a standard time signal. The PTP master clock supports the IEEE 1588 PTP protocol and can send PTP synchronization messages at a preset period to provide a unified time reference for the entire wireless Mesh network.

[0038] As shown in Figure 3 The enhanced Mesh node 3, as the access node or terminal device of the wireless Mesh network, has TSN capability and PTP protocol support, and each node is built-in with a lightweight proxy module, which includes the following functional units: The instruction receiving unit 31 receives the configuration instructions issued by the centralized network controller, including upstream master clock designation, transparent clock mode configuration, delay compensation value, etc., and performs verification and analysis; The state reporting unit 32 periodically collects the state information (signal-to-noise ratio, delay, jitter, packet loss rate, hop count, etc.) of the local link, encapsulates it according to the preset format, and reports it to the centralized network controller. The reporting period can be dynamically adjusted according to the network; The message processing unit 33 supports the transparent clock mode and can record the timestamp of the received PTP message, calculate the residence time, accumulate the correction and forward it, to ensure accurate transmission and delay compensation of the PTP message.

[0039] Embodiment 2

[0040] In order to make the technical solutions of the present application clearer and more complete, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0041] Referring to Figure 4 , the system includes a centralized SDN controller (101), a root gateway (102) as a PTP master clock, and multiple Mesh nodes (103, 104, 105, 106). The controller 101 communicates with all nodes through an out-of-band management channel or a secure in-band channel.

[0042] The implementation process is as follows: After the nodes 103, 104, 105, 106 are connected, they register with the controller 101 and periodically report their neighbor list and the signal-to-noise ratio and delay data of each link.

[0043] The controller 101 calculates a synchronization path for the node 106. Although the node 106 can directly communicate with the node 104, the controller detects that the link between 106 and 104 is unstable, while the signal-to-noise ratio of each link of the path 102->103->105->106 is high. Therefore, the controller decides to use the latter as the main synchronization path.

[0044] The controller 101 issues a configuration to the nodes 103, 105, 106: specifies the upstream master clock of the node 103 as 102; the upstream of the node 105 as 103; and the upstream of the node 106 as 105. And configures these nodes to work in the end-to-end transparent clock mode in accordance with the IEEE 1588 standard.

[0045] The PTP synchronization message is sent from the master clock 102, passes through 103 and 105 to 106. Each transparent clock node will accumulate the residence time of the node in the PTP message. The node 106 can finally calculate the total path delay with the master clock 102 after receiving the message, thereby achieving high-precision synchronization.

[0046] Reference Figure 5 The controller 101 continuously monitors the link quality between the nodes 105 and 106, which suddenly decreases. It immediately performs a switching process: selects the backup path 102->104->106 from the preset backup path library, and instantly issues a configuration update instruction to switch the upstream master clock of the node 106 to 104. This process is completed within milliseconds and has little effect on the local clock synchronization of the node 106.

[0047] The above describes the preferred embodiments of the present application. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be considered within the scope of protection of the present application.

Claims

1. A highly robust PTP time synchronization method for wireless mesh networks, characterized in that, Includes the following steps: Step S1: The centralized network controller acquires the global topology information and real-time link quality information of the wireless mesh network; Step S2: Based on the global topology information and real-time link quality information, dynamically calculate an end-to-end synchronization path to the PTP master clock for each slave clock node in the network. The calculation criteria include one or more of path stability, hop count minimization, and load balancing. Step S3: The configuration information of the end-to-end synchronization path is sent to the relevant Mesh nodes on the path. The Mesh nodes interact with the designated upstream nodes through PTP messages according to the configuration information. The intermediate nodes in the path work in transparent clock mode and perform dwell time accumulation correction on the PTP messages so that the slave clock nodes can achieve end-to-end time synchronization with the master clock based on the corrected messages. Step S4: The centralized network controller continuously monitors the performance of the synchronization path. When the path quality is lower than a preset threshold, it triggers a seamless switch from the primary synchronization path to the backup synchronization path.

2. The method according to claim 1, characterized in that, In step S1, the global topology information is obtained through the registration information and neighbor list collected after the Mesh node comes online. The real-time link quality information includes at least one of the following: link signal-to-noise ratio, transmission delay, jitter, packet loss rate, and hop count. It is periodically reported by the enhanced Mesh node to the centralized network controller.

3. The method according to claim 1, characterized in that, In step S2, the path stability is determined based on the historical quality fluctuation range of the link, and links with fluctuation ranges less than a preset fluctuation threshold are preferentially selected to form a synchronization path. The hop count minimization is achieved by ensuring that the number of hops on the synchronization path does not exceed a preset maximum hop count threshold while meeting path stability requirements; the load balancing is achieved by distributing synchronization traffic to prevent the PTP packet processing load of a single relay node from exceeding its maximum load threshold.

4. The method according to claim 1, characterized in that, In step S3, the configuration information includes an upstream master clock specification instruction, a transparent clock working mode configuration instruction, and an initial path delay compensation value. After receiving the configuration information, the enhanced Mesh node parses and executes the instructions through the proxy module to establish a PTP communication link with the specified upstream node.

5. The method according to claim 1, characterized in that, In step S3, the dwell time accumulation correction in the transparent clock mode is specifically as follows: after the intermediate node receives the PTP message, it records the first timestamp of the message entering the node and the second timestamp of the message leaving the node, calculates the time difference between the two as the dwell time, and writes the dwell time into the reserved field of the PTP message to realize the accumulation of dwell time.

6. The method according to claim 1, characterized in that, In step S4, the synchronous path performance monitoring includes real-time detection of the link's signal-to-noise ratio, transmission delay, jitter, and packet loss rate. The preset thresholds include a minimum signal-to-noise ratio threshold, a maximum delay threshold, a maximum jitter threshold, and a maximum packet loss rate threshold. When any parameter exceeds the corresponding threshold and the duration reaches a preset duration, the path quality is determined to be below the threshold.

7. The method according to claim 1, characterized in that, In step S4, the backup synchronization path is pre-calculated and generated by the centralized network controller when calculating the main synchronization path. The link overlap rate between the backup path and the main synchronization path does not exceed a preset overlap threshold, and the response time for seamless switching does not exceed 10 milliseconds.

8. A highly robust PTP time synchronization system for implementing the method of claim 1 in a wireless mesh network, characterized in that, include: The centralized network controller is used to maintain the global topology information and real-time link quality information of the wireless Mesh network, dynamically calculate the end-to-end synchronization path and distribute configuration information, continuously monitor the performance of the synchronization path and trigger path switching. The PTP master clock serves as the network's time reference, providing a standard time signal. Multiple enhanced Mesh nodes communicate with the centralized network controller. Each enhanced Mesh node contains a proxy module for receiving and executing the controller's configuration instructions, reporting local link status information, and processing PTP packets in transparent clock mode.

9. The system according to claim 8, characterized in that, The centralized network controller includes a topology maintenance module, a link quality monitoring module, a path calculation module, a configuration distribution module, and a path switching module. The topology maintenance module is used to build a dynamic network map. The link quality monitoring module is used to receive and analyze the link parameters reported by the Mesh nodes in real time. The path calculation module is used to execute dynamic path optimization algorithms. The configuration distribution module is used to send configuration commands to the Mesh nodes. The path switching module is used to trigger and execute the path switching process.

10. The system according to claim 8, characterized in that, The proxy module of the enhanced Mesh node includes an instruction receiving unit, a status reporting unit, and a message processing unit. The instruction receiving unit is used to receive configuration instructions issued by the controller. The status reporting unit is used to periodically report the local link status. The message processing unit is used to process PTP messages in transparent clock mode, including timestamp recording, dwell time calculation, and message forwarding.

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