Robust multi-hop time synchronization in sensor networks

Abstract – The possibility of establishing the chronology of events in a widely distributed network, or even stronger, the clock synchronization of all nodes in the network is often needed for applications of wireless sensor networks (WSN). In this paper we describe the Flooding Time Synchronization Protocol (FTSP) that provides clock synchronization service in such networks. The protocol was designed to utilize low communication bandwidth, scale well for medium sized multi-hop networks, and be robust against topology changes and node failures. The robustness of the protocol is due to the periodic radio broadcast of synchronization messages and the implicit dynamic topology update. MAC-layer time-stamping, comprehensive compensation of errors and linear regression are used to achieve high accuracy of the clock synchronization. The data from a comprehensive multi-hop experiment shows that the average network-wide synchronization error is less than two microseconds per hop. The protocol was further validated as part of our countersniper system that was field tested in a US military facility. 1