UAV Relayed Covert Wireless Networks: Expand Hiding Range via Drones

Covert communication has emerged as a revolutionary wireless technique to hide confidential information -- either naturally or via artificial noise -- from being detected. Random transmit power, time-variant channel state information, and location mobility can be leveraged to confuse the detection at the warden. However, it becomes challenging when the distance is long or the direct link is blocked. In this article, we explore an unmanned aerial vehicle (UAV) as the relay to assist covert wireless networks to achieve better quality of service. First, several typical application scenarios are demonstrated and briefly discussed. Then, two scenarios of UAVs serving as a relay in covert wireless networks are narrated. The first case investigates a multi-antenna transmitter aided by a drone relay in the long-range covert wireless network against the detection of a UAV warden. The second case studies the covert wireless network assisted by a UAV relay to overcome the channel blockage problem. Simulation results are provided to evaluate the effectiveness and superiority of the proposed schemes. Finally, some future challenges are discussed.