Throughput Maximization for UAV-Enabled Wireless Powered Communication Networks

摘要

This paper studies an unmanned aerial vehicle (UAV)-enabled wireless poweredcommunication network (WPCN), in which a UAV is dispatched as a mobile accesspoint (AP) to serve a set of ground users. The UAV employs the radio frequency(RF) signals based wireless power transfer (WPT) to charge the users in thedownlink, and the users use the harvested RF energy to send individualinformation back to the UAV in the uplink. Unlike the conventional WPCN withfixed APs, the UAV-enabled WPCN can exploit the mobility of the UAV viatrajectory optimization, jointly with the wireless resource allocation, toimprove the system performance. In particular, we aim to maximize the uplinkcommon throughput among all ground users over a particular finite time period,subject to the UAV's maximum speed constraint and the users' energy harvestingconstraints. The decision variables include the UAV's trajectory design, aswell as the UAV's downlink power allocation for WPT and the users' uplink powerallocation for wireless information transfer (WIT). This problem is non-convexand thus very difficult to be solved optimally. To overcome this issue, wefirst consider a special case when the maximum UAV speed constraint is ignored,and obtain the optimal solution to this relaxed problem. The optimal solutionshows that the UAV should hover above a finite number of ground locations overtime for downlink WPT, and then hover above each user at different time foruplink WIT. Next, based on the optimal multi-location-hovering solution to therelaxed problem, we propose the successive hover-and-fly trajectory, jointlywith the downlink and uplink power allocation, to efficiently solve theoriginal problem with the maximum UAV speed constraint. Numerical results showthat the proposed UAV-enabled WPCN achieves much higher uplink commonthroughput than the conventional WPCN with fixed-location AP.