Joint Trajectory and Resource Optimization for Covert Communication in UAV-Enabled Relaying Systems

A novel covert communication framework is proposed to enhance the privacy of the unmanned aerial vehicle (UAV)-enabled relaying systems. Specifically, the full-duplex (FD) UAV covertly relays data from each ground sensor to remote base station (BS) against a warden (Willie). Considering a noise uncertainty model, the minimum detection error probability (DEP) of Willie is first derived. Under the constraint of the derived DEP, the minimum average covert transmission rate (ACTR) is then maximized by jointly designing the sensor association, the UAV transmit power, and the UAV trajectory. A low-complexity algorithm based on the penalty successive convex approximation (P-SCA) is further invoked to achieve the locally optimal solution. Finally, numerical results show the effectiveness of the proposed framework and reveal some insights, i.e., increasing uncertainty at Willie can improve the covertness performance.