Joint Trajectory and Communication Design for Multi-UAV Enabled Wireless Networks

摘要

Unmanned aerial vehicles (UAVs) have attracted significant interest recentlyin assisting wireless communication due to their high maneuverability, flexibledeployment, and low cost. This paper considers a multi-UAV enabled wirelesscommunication system, where multiple UAV-mounted aerial base stations (BSs) areemployed to serve a group of users on the ground. To achieve fair performanceamong users, we maximize the minimum throughput over all ground users in thedownlink communication by optimizing the multiuser communication scheduling andassociation jointly with the UAVs' trajectory and power control. The formulatedproblem is a mixed integer non-convex optimization problem that is challengingto solve. As such, we propose an efficient iterative algorithm for solving itby applying the block coordinate descent and successive convex optimizationtechniques. Specifically, the user scheduling and association, UAV trajectory,and transmit power are alternately optimized in each iteration. In particular,for the non-convex UAV trajectory and transmit power optimization problems, twoapproximate convex optimization problems are solved, respectively. We furthershow that the proposed algorithm is guaranteed to converge to at least alocally optimal solution. To speed up the algorithm convergence and achievegood throughput, a low-complexity and systematic initialization scheme is alsoproposed for the UAV trajectory design based on the simple circular trajectoryand the circle packing scheme. Extensive simulation results are provided todemonstrate the significant throughput gains of the proposed design as comparedto other benchmark schemes.