Long term and large scale time synchronization in wireless sensor networks

Time synchronization is very important in wireless sensor networks (WSNs). Many applications, for example natural disaster monitoring and structural health monitoring of huge buildings, require a highly accurate, long-term and large-scale time synchronization among the sensor nodes that compose the network. In this paper, we propose a new time synchronization protocol, named 2LTSP (long term and large scale time synchronization protocol), which aims at addressing such requirements. Theoretical analysis and simulation results show that when the synchronization period is less than 100 s, the error of 2LTSP is within 0.6 ms, no matter how large the size of the network is. Besides, when the required synchronization error limit is 9 ms, the communication cost of 2LTSP is less than 3 packets per hour in networks of any size. Therefore, 2LTSP is highly accurate and energy-efficient even for large-scale and long-term running networks.