Recharge scheduling with multiple mobile chargers

This chapter studies the important research scheduling problem for wireless charging in wireless sensor networks.We first present a distributed protocol that can collect energy information from the network on demand. For scalability, the protocol divides the network into hierarchical levels, selects head nodes on each level and establishes routing paths to the heads. Mobile Chargers (MC) send recharge requests to reveal their current locations. Energy information messages then utilize the established routing paths to get back to the MCs. Based on the gathered energy information, our objective is tominimize energy cost for theMCs duringmovements and make sure no sensor depletes battery energy. We formulate the problem into an optimization problem by capturing both battery capacity from theMCs and dynamic lifetime from sensors. Since the problem is NP-hard, we present a three-step adaptive algorithm. The algorithm first partitions energy requests according to their locations. Then it constructs CapacitatedMinimum Spanning Trees to capture charger’s battery capacities. Finally, the algorithm calculates recharge routes for each tree based on node’s lifetime. Simulation evaluations have demonstrated that the algorithm can successfully maintain perpetual operation of the network.