Optimal UAV Route in Wireless Charging Sensor Networks

An unmanned aerial vehicle (UAV) can be utilized as a flying data collector and wireless power source in wireless charging sensor networks (WCSNs). Different from conventional studies that focused on maximizing the efficiency of wireless power transfer (WPT) for UAV route design, in this article, we maximize the lifetime of WCSNs by considering sensor energy consumption and energy harvesting simultaneously. We consider simultaneous wireless information and power transfer (SWIFT), where data collection capability guarantees power leftover for UAV to complete its round-trip flight. Our objective is to jointly optimize the UAV hovering location and duration to maximize the minimum energy of sensors after data transmission and energy harvesting under data collection and UAV energy consumption constraints. To tackle this nonconvex optimization problem, we first assume that the UAV hovering location for each sensor is fixed and optimize UAV hovering duration by the Lagrange multiplier method. Next, for each UAV hovering location, we propose a geometry-based update algorithm, which can be used to find initial feasible UAV routes to the problem. Last, a near-optimal UAV route is determined by adjusting the initial feasible UAV route iteratively, where UAV hovering locations and duration are updated at each iteration. The numerical results are provided to validate the performance of our proposed algorithm.