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

TL;DR

This paper develops an iterative optimization algorithm for joint trajectory, power control, and communication scheduling in multi-UAV wireless networks, significantly improving user throughput and fairness.

Contribution

It introduces a novel joint optimization framework and an efficient iterative algorithm for UAV trajectory, power, and scheduling, with convergence guarantees and a systematic initialization scheme.

Findings

Achieves significant throughput gains over benchmark schemes.

Ensures fair performance among ground users.

Provides a convergent algorithm with practical initialization.

Abstract

Unmanned aerial vehicles (UAVs) have attracted significant interest recently in assisting wireless communication due to their high maneuverability, flexible deployment, and low cost. This paper considers a multi-UAV enabled wireless communication system, where multiple UAV-mounted aerial base stations (BSs) are employed to serve a group of users on the ground. To achieve fair performance among users, we maximize the minimum throughput over all ground users in the downlink communication by optimizing the multiuser communication scheduling and association jointly with the UAVs' trajectory and power control. The formulated problem is a mixed integer non-convex optimization problem that is challenging to solve. As such, we propose an efficient iterative algorithm for solving it by applying the block coordinate descent and successive convex optimization techniques. 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, two approximate convex optimization problems are solved, respectively. We further show that the proposed algorithm is guaranteed to converge to at least a locally optimal solution. To speed up the algorithm convergence and achieve good throughput, a low-complexity and systematic initialization scheme is also proposed for the UAV trajectory design based on the simple circular trajectory and the circle packing scheme. Extensive simulation results are provided to demonstrate the significant throughput gains of the proposed design as compared to other benchmark schemes.