Hybrid Intelligent Reflecting Surface Aided MU-MIMO Secure Communication Systems

The synergy between artificial noise (AN) and intelligent reflecting surface (IRS) has been shown to significantly improve physical layer security (PLS) in wireless networks. In addition, hybrid IRS could enable a trade-off between cost and performance. In this paper, we consider a hybrid IRS-aided multi-user multiple-input multiple-output (MU-MIMO) communication system while a malicious mobile station hovers nearby to eavesdrop on the system. We aim to jointly optimize the BS beamformers for information signals to the legitimate user and AN and the hybrid IRS reflection-amplification coefficients to maximize the secrecy rate (SR) of MU-MIMO communication network. First, we construct the SR optimization problem. The constructed problem is strongly non-convex due to a high correlation between the integrated variables. Next, we develop a low-complexity iterative algorithm based on mean-square error (MSE) and block coordinate descent (BCD) methods to obtain efficient sub-optimal solution to this non-convex problem.