Secure Transmission of IRS-assisted A2G Multiuser Communication System with Hardware Impairments

This paper investigates secure communications in an intelligent reflective surface (IRS)-assisted air-to-ground (A2G) system with hardware impairments (HIs), where an unmanned aerial vehicle (UAV) serves as a base station for multiple ground users in the presence of a ground eavesdropper. We jointly optimize the transmit precoding (TPC) matrix and the IRS phase shift matrix to maximize the sum secrecy rate subject to the transmit power constraint and the IRS unit modulus constraint. The original problem is a non-convex problem that is very difficult to deal with. We solve this problem by alternating optimization (AO) algorithm. We decompose it into two subproblems, which are solved by successive convex approximation (SCA) and semi-definite relaxation (SDR) methods, and optimize these two subproblems alternately. Finally, simulation results reveal the impact of HIs on confidential communication and verify the effectiveness of our algorithm.