Joint Precoding for Intelligent Reflecting Surface-Aided Millimeter Wave Secure Communications

In this paper, we investigate an intelligent reflecting surface (IRS) aided millimeter wave (mmWave) secure communication system. To maximize the secrecy rate at the legitimate receiver, we jointly optimize the active hybrid precoding at the transmitter and passive precoding at the IRS. Since the optimization problem is non-convex, an alternating optimization based algorithm is proposed, i.e., we iteratively solve digital baseband precoding, analog radio frequency precoding or one of the reflection coefficients with the others fixed. Simulation results show that our proposed algorithm can effectively improve the security performance of the system.