Power Minimization for Active IRS Enhanced Directional Modulation Networks

To significantly reduce the total power consumption of the directional modulation network with a given security rate (SR), an emerging active intelligent reflecting surface (IRS) with signal amplifying and forwarding function is introduced into the system in this paper. Specifically, we aim to minimize the total power via jointly designing the confidential message beamforming, artificial noise beamforming, and active IRS reflective beamforming subject to the SR constraint. To address the formulated problem, a scheme for minimizing the total power by alternating optimization (Min-TP-AO) is proposed. Here, the optimization problem is decomposed into three sub-problems with respect to the optimization variables and solved successively by successive convex approximation algorithm. Simulation results show that with the same SR constraint, the proposed scheme significantly outperforms the benchmark schemes in terms of total power consumption.