Covert Transmission Assisted by Intelligent Reflecting Surface

Covert transmission is studied for an intelligent reflecting surface (IRS) aided communication system, where Alice aims to transmit messages Bob without being detected by the warden Willie. Specifically, IRS used increase data rate at under a covert constraint. For considered model, when equipped with single antenna, power and phase shift are jointly optimized maximize either instantaneous or partial channel state information (CSI) of Willie's link. In addition, multiple antennas deployed Alice, we formulate joint beamforming optimization problem rate. One local optimal algorithm two low-complexity suboptimal algorithms proposed solve problem. Furthermore, case imperfect CSI link, reformulated using triangle Cauchy-Schwarz inequalities. The problems solved alternative algorithm, semidefinite relaxation (SDR) Gaussian randomization techniques. Finally, simulations performed verify our analysis. numerical results show that can degrade Willie closer than Bob.