Energy Minimization for UAV Communication Systems Assisted With Multiple IRSs

Abstract

Unmanned aerial vehicle (UAV) communication systems are in active study due to their various applications. However, UAV communication systems suffer from energy consumption, which limits the flight time of UAVs. In this paper, we propose several UAV energy consumption minimization techniques through the aid of multiple intelligent reflecting surfaces (IRSs). In specific, we expand the probabilistic line-of-sight model to capture the characteristics of multiple IRSs and multiple user equipments (UEs). Then, we derive a tight upper bound for the ergodic achievable rate of the UE in a closed form expression, resulting in tractable optimization problems. Accordingly, we solve the optimization problems by adopting the successive convex approximation technique. To compensate for the high complexity of the optimization problems, we propose a low complexity algorithm that has marginal performance loss. In simulation results, we show that the proposed algorithms can significantly save the UAV energy consumption compared to benchmarks, justifying that exploiting the IRSs can indeed decrease UAV energy consumption.