Study On Consensus-Based Clock Synchronization Methods For Wireless Sensor Networks Under Random Delays

Clock synchronization is one of the key technologies to support the stable operation of wireless sensor networks.Consensus-based clock synchronization is a distributed clock synchronization mechanism,which introduces the consensus algorithm in the process of clock parameters compensation,and achieves the convergence of the entire network synchronization through the information exchange between neighboring nodes.In recent years,consensus-based clock synchronization has gained popularity for its robustness,scalability,and simple network-wide synchronization.Communication delay is an important challenge for clock synchronization.However,most of the current consensus-based clock synchronization methods lack sufficient consideration and effective utilization of communication delays and their distribution characteristics,which influences the synchronization performance under delays.Therefore,in order to solve above problems,this thesis researches consensus-based clock synchronization methods with random delays.The main contributions of this thesis are as follows:1.This thesis studies the the fundamental technologies related to consensus clock synchronization in wireless sensor networks,and analyzes the basic model of consensus-based clock synchronization,the influence of communication delay in the process of synchronization message interaction,and the basic classification of consensus clock synchronization.2.For the problem that the existing consensus clock synchronization methods do not pay attention to the compositions and distribution characteristics of the delay,this thesis proposes weighted-median-based consensus clock synchronization algorithms.Based on data processing optimization methods and different requirements,two different relative skew estimation methods are proposed under the fixed delay and bounded exponential random delay.The gap based weighted median estimation method can improve the estimation accuracy,while the threshold weighted median estimation method can reduce storage overhead.Then,the estimated relative skew is used to the consensus compensations of the logical clock skew and offset to realize the network-wide clock synchronization.Simulation is presented to verify the effectiveness of the proposed consensus synchronization method.3.In order to further improve the consensus synchronization accuracy,a maximum likelihood estimation based consensus clock synchronization algorithm is proposed.According to the distribution characteristics of random delays,the maximum likelihood method is used to estimate the relative skew and other unknown clock parameters jointly,then the estimation is transformed into a linear optimization problem.A recursive method is presented to compute the clock parameters of maximum likelihood estimation,which reduces storage overhead and calculation cost.Then the average consensus method is adopted to compensate the synchronization parameters.Theoretical proof and simulation verify the synchronization convergence.Simulation results reveal that the consensus clock synchronization algorithm proposed in this thesis can effectively converge under time delay,and the synchronization accuracy is better than other similar works.It means that the analysis and utilization of communication delay components and characteristics in this thesis effectively improve the performance of consensus clock synchronization.Therefore,the research results of this study have certain reference value for consensus clock synchronization in wireless sensor networks.