Optimization algorithms for transmission range and actor movement in wireless sensor and actor networks

Wireless sensor and actor networks are composed of static sensors and mobile actors. We assume actors have a random initial location in the two-dimensional sensing area. The objective is to move each actor to a location such that every sensor node is within a bounded number of hops from some actor. Because sensors have limited energy, the new actor locations are chosen to minimize the transmission range of the sensors. However, actors also have a limited (although larger) power supply, and their movement depletes their resources. It follows that by carefully choosing the new actor locations, the total actor movement can be minimized. In this paper, we introduce the problem of simultaneously minimizing the required transmission range and amount of actor movement. To find a solution, we formulate the problem using an ILP framework. For the ILP solution to be feasible, we introduce a finite set of possible actor locations such that an optimal solution is guaranteed to be found within this set. We also present a heuristic for this problem. As a preliminary step, we study minimizing the transmission range necessary for multi-hop communication. Various heuristics for this smaller problem are proposed and their results are compared by simulation. The best of these heuristics is then enhanced to incorporate minimizing the movement of actors, and its performance is compared to the optimal ILP solution.