A Time Synchronization Mechanism Based Doppler For Mobile Underwater Sensor Networks

With the rapid development of network technology, wireless sensor networks (WSNs)are widely used in various fields. Due to the marine technology and military demand, the underwater sensor acoustic networks (UWSNs) have gradually developed. Compared with terrestrial wireless sensor network, UWSNs are mainly used in underwater acoustic communication due to the electromagnetic wave attenuation in the water and they have characteristics of high propagation delay and uncertainty. In order to solve the impact of high propagation delay on time synchronization, a time synchronization algorithm is proposed,which is assumed to keep the relative uniform motion in time synchronization process. But this assumption needs to be considered in the complex and changeable underwater environment.In order to solve the problem of high propagation delay and uncertainty in UWSNs, the paper proposes a Doppler auxiliary time synchronization algorithm (DATS). The algorithm uses autonomous underwater vehicle (AUV) as a beacon node. The beacon node and common node carry out information exchange to complete the whole time synchronization process, the main steps include information exchange based Doppler between the nodes and the calculation of the clock shew and offset. The information exchange between nodes is mainly used to collect data. The beacon node periodically broadcasts the information with time stamp.The ordinary node records the time of receiving the information and the relative speed with Doppler shift between ordinary node and beacon node; in the phase of calculation clock skew and offset, based on the collected data and the distance between the beacon node and ordinary node,the ordinary nodes compute clock skew and offset. Finally, in simulation experiment,compared with the energy efficiency distributed time synchronization (E2DTS), DATS had better performance in some time synchronization performance parameters.