On Efficient UAV Charging Trajectory for Large-scale Wireless Sensor Networks

Limited battery capacity is one of the most critical factors to hinder the development of Wireless Sensor Networks (WSNs). In recent years, the breakthrough in rechargeable batteries and wireless energy transfer technology provides a promising solution for replenishing sensors wirelessly. The existing researches only paid their attention to reducing the UAV travelling distance, while the UAV charging efficiency is overlooked. To fill this gap, we devote this paper to developing an Efficient UAV Charging Trajectory scheme (EUCT) for largescale WSNs. Technically, we first formulate a dual-objective optimization problem to minimize the number of the dead nodes and maximize the UAV charging efficiency. In order to solve this problem, a series of algorithms are proposed. Specifically, a coarse trajectory construction algorithm is first presented to form a basic feasible charging path. In order to improve the UAV charging efficiency, a trajectory refinement algorithm is then developed. Subsequently, a global trajectory optimization scheme is further proposed to minimize the number of the dead nodes. The simulation results demonstrate that our EUCT scheme performs best in terms of the node survival rate and the UAV charging efficiency.