Simultaneous optimization of transmission range and actor movement in WSANs

Wireless sensor and actor networks (WSANs) are composed of static sensor nodes and movable actors. We assume actors have a random initial location in the field. The objective is to move each actor to a location such that every sensor node is within one transmission hop from some actor. Because sensor nodes have limited energy, finding actor locations that minimize the transmission range required from the sensor nodes may significantly increase network lifetime. However, actors also have a limited (although larger) power supply, and their movement depletes their resources. It follows that an optimal pairing of actors with the chosen new locations may also provide energy savings for the actors. In this paper, we address the problem that simultaneously minimizes sensor transmission radius and total actor movement. Due to its complexity, we present a heuristic and compare it against an optimial ILP solution. More importantly, we consider two approaches for both the heuristic and the ILP. First, actor locations that minimize transmission range are found, and then the assignment of actors to locations is performed (double-step approach). Second, a joint-optimization (single-step) approach is proposed in which transmission range and actor movement are considered simultaneously. We show that the single-step approach outperforms the double-step approach.