Directional Modulation-Enabled Secure Transmission with Intelligent Reflecting Surface

We propose a new secure transmission scheme which uses directional modulation (DM) with artificial noise and is aided by the intelligent reflecting surface (IRS). Specifically, the direct path and IRS-enabled reflect path carry the same confidential signal and thus can be coherently added at the desired position to maximize the total received power, while the received signals at other positions are distorted. We derive a closed-form expression for the secrecy rate achieved by the proposed scheme. Using simulation results, we show that the proposed scheme can achieve two-dimensional secure transmission at a specific position. Also, its performance advantage over the conventional DM scheme becomes more pronounced as the number of reflecting elements at the IRS increases.