This paper studies a new unmanned aerial vehicle (UAV)-enabled wireless power
transfer (WPT) system, where a UAV-mounted mobile energy transmitter (ET) is
dispatched to deliver wireless energy to a set of on-ground energy receivers
(ERs). We investigate how the UAV should optimally exploit its mobility via
trajectory design to maximize the energy transferred to all ERs during a finite
period. First, we consider the maximization of the sum energy received by all
ERs by optimizing the UAV's trajectory subject to its maximum speed constraint.
We obtain its optimal solution, which shows that the UAV should hover at one
single fixed location during the whole period. However, the sum-energy
maximization incurs a "near-far" fairness issue. To overcome this issue, we
consider a different problem to maximize the minimum received energy among all
ERs. We first consider an ideal case by ignoring the UAV's maximum speed
constraint, and show that the relaxed problem can be optimally solved via the
Lagrange dual method. Then, for the general case with the UAV's maximum speed
constraint considered, we propose a new successive hover-and-fly trajectory
motivated by the optimal trajectory in the ideal case, and obtain efficient
trajectory designs by applying the successive convex programing (SCP).

本文研究一种新型无人机无线电能传输系统，通过优化其轨迹设计，使得无人机最大化地利用其移动性来向一组地面能量接收器输送无线能量，从而解决了无人机提供能量传输的距离分布不均的问题，并提出了一种基于连续凸规划的优化方案。