Practical Concurrent Wireless Charging Scheduling for Sensor Networks

In complex terrain where mobile chargers hardly move around, a feasible solution to charge wireless sensor networks (WSNs) is using multiple fixed chargers to charge WSNs concurrently with relative long distance. Due to the radio interference in the concurrent charging, it is needed to schedule the chargers so as to facilitate each sensor node to harvest sufficient energy quickly. The challenge lies that each charger's charging utility cannot be calculated (or even defined) independently due to the nonlinear superposition charging effect caused by the radio interference. In this paper, we model the concurrent radio charging, and formulate the concurrent charging scheduling problem (CCSP) whose objective is to design a scheduling algorithm for the chargers so as to minimize the time spent on charging each sensor node with at least energy E. We prove that CCSP is NP-hard, and propose a greedy algorithm based on submodular set cover problem. We also propose a genetic algorithm for CCSP. Simulation results show that the performance of the greedy CCSP algorithm is comparable to that of the genetic algorithm.