Joint Beamforming and Trajectory Optimization for Intelligent Reflecting Surfaces-Assisted UAV Communications

Linghui Ge,Hua Zhang,Xiaohu You,Jun-Bo Wang,Peihao Dong

doi:10.1109/access.2020.2990166

Abstract

Unmanned aerial vehicle (UAV) and intelligent reflecting surface (IRS) are anticipated to be widely applied for improving the spectrum and energy efficiency in the forthcoming wireless communication systems. To take full advantages of IRS-assisted UAV system, both beamforming and UAV’s trajectory should be optimally designed. In this paper, we consider a challenging scenario where there are one UAV and several IRSs. For the IRSs-assisted UAV system, we formulate the problem as maximizing the received power at the ground user by jointly optimizing active beamforming at the UAV, passive beamforming at the IRSs, and UAV’s trajectory over a given flying time. An efficient framework is proposed so that the joint optimization problem can be decomposed into three subproblems, which can be iteratively optimized individually. In particular, a closed-form expression is derived for updating the phase shifts of the reflecting elements, which helps develop a low-complexity algorithm. Numerical results show that our scheme outperforms other benchmark schemes, which corroborates the feasibility and effectiveness of our proposed algorithm.

Highlights

Unmanned aerial vehicles (UAVs), commonly known as aerial base stations (BS), have attracted significant attention in the past decade for various applications
UAVs can be employed as aerial communication platforms to improve the performance of the existing terrestrial wireless communication systems, such as cellular networks [2]
We assume that there are two intelligent reflecting surface (IRS) in our simulation and the number of IRSs can be extended to a general value

Summary

Introduction

Unmanned aerial vehicles (UAVs), commonly known as aerial base stations (BS), have attracted significant attention in the past decade for various applications. Equipped with advanced transceivers and batteries, UAVs are getting popularity in relaying, data gathering, secure transmission, and information dissemination [1]. UAVs have high possibilities to have line-of-sight (LoS) communication links due to the high maneuverability and flexibility for ondemand deployment. UAVs can be employed as aerial communication platforms to improve the performance of the existing terrestrial wireless communication systems, such as cellular networks [2]. The UAV communication faces many challenges, especially in urban areas. One prominent challenge is blockage [3] caused by common objects, such as buildings, trees, and human bodies, which can proliferate problems with coverage and connectivity. Excessive spatial and temporal variations of the non-stationary channels [4] are caused by the mobility of both the UAV and the ground

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Results

Conclusion