Secondis: An Adaptive Dissemination Protocol for Synchronizing Wireless Sensor Networks

Reliability and predictability of the timing behavior have shown to be major issues for wireless sensor network deployments. Real-time requirements presented by several applications can be fulfilled by implementing communication schemes that lower possible sources of non-determinism of the timing behavior, assuming that the nodes are synchronized. The predictability of current synchronization protocols, however, cannot be verified, due to potential interferences with other activities. In this paper we propose Secondis, a dissemination protocol that periodically synchronizes and orchestrates activities in the network, providing three main benefits. (1) The synchronization task is performed in short time windows, where no interferences can occur, independently of any available communication structure. (2) The synchronization is energy efficient, and (3) robust against link and node failures. Secondis provides probabilistic bounds about its predictability, by means of a probabilistic model checker analysis. It proposes a novel adaptive flooding scheme based on the observation that only a subset of the nodes is important for the propagation. The behavior is analyzed in simulation, using realistic models of the wireless channel and hardware clocks.