Research On Time Synchronization Technology In Wireless Time-Sensitive Network

As a type of deterministic network technology,Time Sensitive Network(TSN)provides deterministic data transmission capabilities for application scenarios with high requirements for network low latency,high reliability and high stability.With the development of wireless communication technology,how to develop wireless TSN for Wireless Local Area Network(WLAN)has become one of the directions of TSN standardization process.In wireless TSN systems,accurate time synchronization is crucial for reducing frame spacing and improving the performance of the wireless system.However,wireless communication poses significant challenges in ensuring the accuracy of time synchronization due to bandwidth resource constraints and channel randomness.The revised version of the time synchronization specification in the TSN protocol family,IEEE 802.1AS-2020,has selected Fine Time Measurement(FTM,used for ranging and positioning in WLAN)as the specification for time synchronization in wireless networks.This paper focuses on FTM and conducts research from three aspects:FTM protocol improvement,accuracy of the time synchronization,reliability of the time synchronization.Simulation experiments are conducted based on the network simulation platform OMNET++.The specific work of this paper is as follows:(1)Improve the FTM protocol to save bandwidth.Based on the characteristics of broadcast communication in wireless networks,this paper proposes an improved FTM protocol named advertisement based FTM protocol(a-FTM).In a-FTM we use a new local clock correction algorithm based on link delay calculation.In the network simulation platform OMNET++,communication frameworks for FTM and a-FTM are designed based on INET.Theoretical and simulation experiments have shown that the a-FTM protocol can reduce the convergence time and number of packets required for synchronization without affecting synchronization accuracy.(2)Improve time synchronization accuracy.To eliminate the impact of randomness in wireless channels on time synchronization accuracy,this paper proposes a path asymmetry(PA)pretreatment method based on a-FTM and stacked denoising autoencoder.The Kalman filter based time synchronization algorithm is selected as the baseline algorithm,and the effectiveness of the method is verified by comparing the time synchronization performance before and after adding PA pretreatment to the baseline algorithm.The experimental results show that the baseline algorithm with PA pretreatment has improved the accuracy and precision of time synchronization,and can achieve high time synchronization accuracy under various clock models and working conditions.(3)Improve the reliability of time synchronization.This paper analyzes the multi domain redundancy mechanism proposed by IEEE 802.1AS-REV and designs a multi domain redundancy fusion algorithm based on federated Kalman filtering.The algorithm can dynamically model the clock behavior of each domain based on factors such as convergence time,and weight the fusion filtering results based on the observation noise of each subsystem.The experimental results show that this algorithm can dynamically combine redundant information from multi domains based on the measurement noise model,and has the ability to quickly adjust synchronization results when some network failure occurs.