P&;P: an asynchronous and distributed protocol for mobile sensor deployment

The use of wireless mobile sensors is of great relevance for a number of strategic applications devoted to monitoring critical areas where sensors can not be deployed manually. Mobile sensors can adapt their position on the basis of a local evaluation of coverage, thus permitting an autonomous deployment. Several algorithms have been proposed to deploy mobile sensors over an area of interest. The applicability of these approaches largely depends on a proper formalization of rigorous rules to coordinate sensor movements, solve local conflicts and manage possible failures of communications and devices. In this paper we introduce P&P, a communication protocol that permits a correct and efficient coordination of sensor movements in agreement with the Push & Pull algorithm. We deeply investigate and solve the problems that may occur when coordinating asynchronous local decisions in the presence of an unreliable transmission medium and possibly faulty devices such as in the typical working scenario of mobile sensor networks. Simulation results show the performance of our protocol under a range of operative settings, including conflict situations and irregularly shaped target areas. Furthermore, a performance comparison between the P&P protocol and one of the best solutions based on the virtual force approach, shows the superiority of our proposal in terms of deployment time, message exchanges and energy consumption.