Physical Layer Security in UAV Systems: Challenges and Opportunities

Unmanned aerial vehicle (UAV) wireless communications has experienced an upsurge of interest in both military and civilian applications, due to its high mobility, low cost, on-demand deployment, and inherent line-of-sight air-to-ground channels. However, these benefits also make UAV wireless communication systems vulnerable to malicious eavesdropping attacks. In this article, we aim to examine the physical layer security issues in UAV systems. In particular, passive and active eavesdropping are two primary types of attack in UAV systems. We provide an overview on emerging techniques, such as trajectory design, resource allocation, and cooperative UAVs, to fight against both types of eavesdropping in UAV wireless communication systems. Moreover, the applications of non-orthogonal multiple access, multiple-input multiple-output, and millimeter-wave in UAV systems are also proposed to improve the system spectral efficiency and to guarantee security simultaneously. Finally, we discuss some potential research directions and challenges in terms of physical layer security in UAV systems.