AbstractTime synchronization in mobile underwater wireless sensor networks (UWSNs) faces two major challenges, namely, long propagation delay and node mobility. In this paper, a Chirp-based broadcasting time synchronization (CB-Sync) algorithm based on unidirectional broadcast mechanism of a spread spectrum signal, i.e., Chirp, is proposed. The CB-Sync algorithm uses the clock frequency offset and phase offset of the Chirp at the physical layer to reduce errors caused by mobility of the nodes. Furthermore, CB-Sync algorithm uses a periodic one-way broadcast mechanism to synchronize neighboring nodes. According to the received broadcast information, the neighboring node obtains the initial frequency clock skew and offset by two linear regressions. Finally, a minimum gradient descent algorithm is used to reduce errors caused by Doppler shift to improve accuracy of time synchronization. Simulation results show that the CB-Sync algorithm can achieve higher energy efficient and better time synchronization accuracy.
Received: 07 December 2016
Published: 24 December 2018