A survey of covert UAV communications^☆

Unmanned aerial vehicles (UAVs), characterized by their low cost and operational flexibility, have been increasingly deployed across civilian, military, and commercial applications. To improve the coverage and connectivity, UAVs can be utilized to realize the comprehensive spatial coverage for the sixth-generation mobile networks. However, the private data in UAV networks is easy to be exposed due to the light-of-sight links and openness of wireless transmission. Covert communication as an emerging technique has shown its superiority in hiding the transmission behavior, which can further enhance the security of UAV networks compared with the traditional physical-layer security. Therefore, in this article, we present a survey on the recent advanced research about covert UAV communications. First, the roles of UAVs for covert communications are described. Then, the covert UAV communications with different uncertainties are introduced. Moreover, the wireless techniques for covert UAV communications are explored. In addition, we point out the applications in covert UAV communications. Finally, the open research issues concerning practical scenarios and promising applications are highlighted.