UAV-IRS Assisted Covert Communication: Introducing Uncertainty via Phase Shifting

The line-of-sight (LoS) channels introduced by unmanned aerial vehicle (UAV) may lead to the threat of being detected, and thus fail the covert communication. This can be solved by intelligent reflection surface (IRS) to introduce additional randomness. In this letter, we propose a novel scheme via a UAV carrying an IRS to establish air-ground links to assist the covert transmission, where the phase shifts of IRS are randomized to preserve the covertness. In addition, the legitimate receiver can act as a jammer in the full-duplex mode to defuse the detection of a warden. An optimal detection threshold and the corresponding error detection probability are derived. Under this worst situation, the optimal transmit-to-jamming ratio is obtained to maximize the achievable transmission rate. Simulation results are presented to show the effectiveness of the proposed UAV-IRS assisted covert communication scheme.