Research On Fault-tolerant Of Time Synchronization Algorithm For Wireless Sensor Networks

Time synchronization technology plays an important role in Data aggregation,Node distribution tracking,Routing selecting,Transmission scheduling and other applications of wireless sensor networks.The study of high precision time synchronization technology has become a hot topic in recent years.Because Wireless sensor network nodes are usually deployed in harsh environmental conditions and the data transmission between nodes is vulnerable to interference from various external environmental factors,so the focus of this thesis is how to ensure that the node is still fault-tolerant to transmit safe and reliable information when the communication data is disturbed.In the classical synchronization protocol,the flooding time synchronization protocol(FTSP)takes into account the synchronization accuracy,energy consumption,robustness and scalability.Thus this thesis is analyzed and improved many aspects based on the FTSP protocol.Being considered the protocol very little in the node time synchronization fault tolerance,this paper has done the following aspects of work.(1)FTSP uses linear regression to estimate the clock drift rate,but the estimation method is susceptible to abnormal data and the estimated value fluctuates greatly.In order to solve this problem,this thesis proposes a dynamic weighted average algorithm to solve the new drift value by adding a finite clock drift rate.The weighting coefficient of the new algorithm is determined by the dynamic time between nodes,which make the abnormal data has little effect on the linear regression on the estimated value,so as to achieve the purpose of improvement.(2)In view of the problem that the error of wireless sensor network increases with the increasing of node hops,this thesis uses multi-source system instead of traditional single source system to reduce the hop number of nodes,which reduce the cumulative error of nodes.In the same network topology,the average hops and the maximum hops of the multi-source system are lower than the single source system,and the cumulative error of the nodes is obviously reduced by the experimental simulation.(3)A anti-attack algorithm of multi-source is proposed to the multi-source system.The algorithm adds two fields to the FTSP original synchronization information,that is the sending node ID and the blacklist.According to the rate difference of the same node in two consecutive cycles of clock drift determines the sending node properties,when the difference value is greater than the pre-set gate value,the sender node is considered as a malicious node,and the node's ID number is send out by adding to the blacklist,notifying the synchronization of the node to refuse to accept malicious nodes of the synchronization information,so as to improve the robustness and security of the system.Finally,the simulation results show that the improved time synchronization algorithm has a great improvement in time synchronization error,fault tolerance and security.