Age of Information Minimization in UAV-Assisted Covert Communication: Trajectory and Beamforming Design

Covert communication is an emerging security solution to prevent or decrease the warden’s detection rate. Unmanned aerial vehicle (UAV), as an aerial covert transmitter, should jointly optimize the trajectory to ensure covertness. The eavesdropper-equipped UAV attempts to adversarially detect covert communication by adjusting its distance and setting the detection threshold. Due to the variation of the air-to-ground channel, the data status may have an expiration time. Information freshness is important in guaranteeing covertness, such as identifying threats and tracking movements. To quantify information freshness, age of Information (AoI), is represents the elapsed time since the most recent successfully decoded information was updated. We investigate UAV-assisted covert communication to minimize AoI with an aerial eavesdropper for the first time. However, to ensure the eavesdropper’s error detection rate, UAV-enabled beamforming employs the power-domain non-orthogonal multiple access (PD-NOMA) technique to cover the covert user by a public user. PD-NOMA technique significantly improves the user’s AoI, too. The joint optimization problem contains non-convex constraints and coupled optimization variables, including UAV trajectory, beamforming design, and the user’s AoI. We have developed an efficient alternating optimization technique to address it. Numerical results demonstrate the impact of the main parameters on the performance of the proposed system.