Covert Communication in Intelligent Reflecting Surface-Assisted NOMA Systems: Design, Analysis, and Optimization

In this paper, we investigate covert communication in an intelligent reflecting surface (IRS)-assisted non-orthogonal multiple access (NOMA) system, where a legitimate transmitter (Alice) applies NOMA for downlink and uplink transmissions with user (Bob) public (Roy) aided by IRS. Specifically, propose new IRS-assisted schemes to hide the existence of Bob’s transmission from warden (Willie), which cost-effectively exploits phase-shift uncertainty IRS signal Roy as cover medium without requiring additional sources. Assuming worst-case scenario Willie can optimally adjust detection threshold his detector, derive analytical expression minimum average error probability achieved each proposed schemes. To further enhance performance, maximize rates Bob jointly optimizing transmit power reflect beamforming, subject given requirements on covertness against quality-of-service at Roy. Simulation results demonstrate advantage confirm accuracy derived results. Interestingly, it is found that impossible using or considered setup while always guarantee positive rates.