An Asynchronous Clock Offset and Skew Estimation for Wireless Sensor Networks

Time Synchronisation is one of the fundamental technologies in Wireless Sensor Networks (WSNs). However, most of the existing research focuses on clock estimation and message exchange to increase the synchronisation accuracy without taking network performance as the primary consideration. To improve the network energy conservation while balancing the time synchronisation accuracy, this paper introduces a new clock offset and skew estimation system for WSNs including a system model, a clock offset estimation method and a skew estimation method. The system adopts a sparse mesh network structure for establishing sensor node connections. In particular, the clock offset estimation uses a data preprocessing procedure to deal with missing data and outliers. The offset estimation considers both start-up delays and clock drifts. Local clock offsets and skews are estimated by timestamps from previous transmissions, even the current state of the transceivers is off. By carrying out a set of simulation experiments based on Network Simulator 2 (NS2), we show that the energy consumption of the individual sensor nodes is decreased with an acceptable time error rate.