Low-overhead time synchronization for schedule-based multi-channel wireless sensor networks

Network-wide time synchronization is essential for schedule-based communication in multi-channel wireless sensor networks (WSN). However, broadcast communication, used by many time synchronization protocols, is not fully supported in networks of this type. This poses a difficulty in distributing the global timing information over the complete network to achieve network-wide synchronization. To overcome this problem, a time synchronization scheme is needed that uses parallel communication on multiple channels for disseminating the timing information. Located at the medium access control (MAC) layer, the scheme can obtain more precise clock offset estimation. Besides, the timing information is piggybacked on MAC layer control messages, the time synchronization scheme does not induce extra messages. Experimental evaluation results from real hardware have shown that the scheme achieves a very high accuracy with an acceptable overhead. This proves that the deployment of several proposed schedule-based multi-channel MAC protocols is practically feasible without threatening the energy consumption of the network.