Research On Clock Synchronization For AUV-assisted Underwater Wireless Sensor Networks

As an important technology of underwater wireless sensor networks,clock synchronization provides a unified reference clock for multiple nodes in the network,thus effectively cooperating with nodes.AUV-assisted underwater wireless sensor networks can improve the data aggregation efficiency,data transmission rate and positioning accuracy of underwater applications by using AUV.However,the mobility of AUV will seriously affect the clock synchronization performance of sensor nodes.Therefore,this thesis deeply studies the clock synchronization in the AUV-assisted underwater wireless sensor network.In this thesis,three aspects of AUV-assisted clock synchronization in underwater wireless sensor networks are studied.Firstly,we analyze the influencing factors of clock synchronization in AUV assisted underwater wireless sensor networks.Based on the data in underwater acoustic network and AUV moving path,the quantitative analysis of propagation delay based on the underwater acoustic stratification effect is carried out,and the synchronization scheme under AUV horizontal scheme,which limits the underwater acoustic stratification effect,is proposed.Secondly,for the asymmetry problem of AUVassisted synchronous communication link,the one-way propagation delay estimation method is studied based on node deployment and AUV-assisted path planning,and we propose the AUV-assisted clock synchronization algorithm,Asy-Sync.By analyzing the influence of parameters on the algorithm,an appropriate parameter combination is determined to compare its synchronization performance with other synchronization algorithms.Compared with other algorithms,Asy-Sync algorithm effectively improves the clock synchronization accuracy,and the cumulative speed of synchronization error is less than 1 / 10 of that of other algorithms.Thirdly,two schemes are proposed to solve the of the energy consumption problem of AUV-assisted underwater synchronous networks,including AUV path optimization and dynamic adjustment of resynchronization cycle.Among them,the AUV path optimization mechanism improve the mobile path by selecting virtual cluster nodes based on the immune algorithm,so as to balance the energy consumption.In order to meet the requirement of the network clock synchronization accuracy,the dynamic adjustment mechanism for the resynchronization period is applied,which sets the resynchronization period through the clock errors accumulated by sensor nodes after the last clock synchronization.On this basis,the clock synchronization algorithm based on energy consumption optimization,Le-Sync,is proposed,and simulation experiments show that the energy consumption of Le-Sync algorithm is only 1/3 of that of the Asy-Sync algorithm.In this research,we propose the AUV-assisted clock synchronization technology for underwater wireless sensor networks.And the algorithms provide a new method to improve clock synchronization accuracy and reduce energy consumption in underwater wireless sensor networks.