Guard Beacon: An Energy-Efficient Beacon Strategy for Time Synchronization in Wireless Sensor Networks

In this paper, we present Guard Beacon, which is a beacon strategy to reduce the energy consumption of time synchronization in wireless sensor networks (WSNs). In a low duty-cycled sensor network, a node may miss incoming synchronization beacons because of wrong active/sleep mode due to clock drift. Therefore, it is critical to guarantee that beacons arrive at the receiver at the right time. The proposed method, i.e., Guard Beacon, can reduce the overall power consumption of synchronization while guaranteeing a very high probability that the synchronization packet is received, by sending multiple beacons within a synchronization round. By investigating on the energy tradeoff between sending and receiving beacons, we find an optimal iterative solution as well as a suboptimal analytical solution as to how many beacons should be sent and when to send them. The strategy is implemented in a real-world testbed for experiment validation. The results show that the proposed Guard Beacon may save more than 40% synchronization power consumption compared with the existed Single Beacon strategy and is also more energy efficient than RTSP in multihop networks.