Relaying IRS-UAV Assisted Covert Communications in Uplink C-NOMA Network

In this letter, a covert communication scheme assisted by a relaying unmanned aerial vehicle (UAV) equipped with an intelligent reflection surface (IRS) is proposed. Specifically, in the uplink clustered non-orthogonal multiple access (C-NOMA) network, the UAV forwards confidential information from legitimate users (LUs) to the authorized receiver (Bob) while avoiding the warden's detection. To maximize the average downlink covert rate (ADCR) at Bob under the covertness constraint, a joint optimization problem with respect to IRS phase shift matrix, LUs' transmit power and UAV trajectory is formulated. The original problem is transformed into a convex form leveraging the Taylor expansion and relaxation variable method, and then an iterative algorithm is proposed. Numerical results validate that the proposed scheme significantly improves ADCR compared with the benchmarks.