Intelligent Reflecting Surface-aided Robust Directional Modulation with Hardware Impairments

In practice, hardware impairments of physical-layer secure communication systems are inevitable. Residual hardware impairments of the transceiver inevitably result in distortion noise, leading to performance loss. In this study, we focus on a multiple-input multiple-output communication system with distortion noise that utilizes both intelligent reflecting surface (IRS) and directional modulation (DM) for secure transmission. DM can prevent eavesdropping, ensuring the safety of legitimate users. IRS aids transmission from base stations to users, playing a crucial role in complex wireless environments. We explore a robust transmission design and propose an efficient algorithm for solving non-convex problems by the alternative iterative method to maximize the secrecy rate. Specifically, we use the successive convex approximation to solve the directional modulation optimization problem and the semidefinite program method to obtain the phase shift of the IRS. Simulation results show that the proposed algorithm can achieve significant performance improvement compared to conventional non-robust schemes.