Adaptive synchronization for duty-cycling in environmental wireless sensor networks

In wireless sensor networks, as energy limited systems, communication is a costly activity. For this reason duty cycling approaches are commonly used, because they can limit the overall power consumption of a sensor node tremendously by shutting down communication sub-circuits whenever they are not used. However, for efficient power reduction nodes have to know the exact times when they are supposed to communicate in the network. Synchronization can be used to accomplish this and comes with additional features such as the possibility of cooperative sampling at a given time. In this paper we propose a synchronization protocol that introduces low overhead due to broadcast master-node synchronization, while still accomplishing synchronization accuracies in the order of 100 ¿s. The protocol is intended for periodic data collection applications that are common tasks in environmental monitoring systems. Since changes in environmental conditions can have a large effect on the synchronization behavior, we further present a temperature compensation algorithm for the proposed synchronization protocol that allows stable usage of synchronization in a wide range of temperatures. Measurement results are taken from implementing the protocol on sensor node platforms and show the real world performance of the presented methods.