Research And Implementation Of Wireless Time Synchronization Technology For Distributed Collaborative Communication

Time synchronization technology provides a unified global clock scale for distributed collaborative systems,which is the key to ensuring distributed nodes can coordinate communication and data fusion.With the rapid development of communication technology,many Io T devices are connected to the network wirelessly.Time synchronization technology based on a wired network has been unable to meet the needs of synchronization accuracy and wireless synchronization.Simply using hardware to improve synchronization accuracy also has particular bottlenecks.Therefore,studying the wireless time synchronization technology and optimization method suitable for distributed systems is significant.Based on the wireless distributed cooperative communication requirements,this thesis analyzes the synchronization module delay and the synchronization error caused by the wireless transmission link delay and designs a time synchronization optimization algorithm to improve the time synchronization accuracy.The main contents of this thesis are as follows:1.The factors influencing nonlinear synchronization such as wireless transmission link delay,hardware forwarding delay and frequency stability are analyzed,and a nonlinear time synchronization model is established.This work lays a foundation for the subsequent design of nonlinear synchronous optimization algorithms.2.Aiming at the decrease of filtering accuracy caused by unknown measurement noise,a Variational Bayesian-Adaptive Unscented Kalman Filtering(VB-AUKF)synchronization optimization algorithm based on the unscented Kalman filtering framework is proposed.The algorithm uses the variational Bayesian method to complete the adaptive estimation of the measurement noise covariance and realizes the prediction and estimation of the synchronization time offset of the master and slave nodes.The simulation results show that the adaptive algorithm can effectively improve the time synchronization accuracy.3.A Variational Bayesian-Adaptive Robust Unscented Kalman Filter(VB-ARUKF)synchronization optimization algorithm is proposed for outliers in the synchronization process.Based on the VB-AUKF algorithm,the algorithm combines the maximum a posteriori estimation method to realize the simultaneous estimation of the covariance of process noise and measurement noise.Based on the Gaussian statistical properties of the innovation sequence,the threshold and the window sliding mean are used to determine and smooth out outliers.Simulation results show that in the presence of unknown noise and outliers,the synchronization process of the algorithm shows higher synchronization accuracy,faster convergence speed and less time-deviation group.4.Complete the design and implementation of the time synchronization system,and embed the synchronization optimization algorithm into the synchronization protocol stack for synchronization optimization.The test results show that the time synchronization accuracy after optimizing the algorithm is improved by magnitude.The time synchronization optimization algorithm studied in this thesis can significantly improve the time synchronization accuracy of wireless nodes and improve the convergence speed and stability of the synchronization process,which is of great significance for the study of distributed cooperative communication.