As an excellent tool for aiding communication, intelligent reflecting surface (IRS) can extend the coverage area, remove blind area, and achieve a dramatic rate improvement. In this paper, we improve the secret rate (SR) performance at directional modulation (DM) networks using IRS. To fully explore the benefits of IRS, two efficient methods are proposed to enhance SR performance. The first approach computes the confidential message (CM) beamforming vector by maximizing the SR, and the signal-to-leakage-noise ratio (SLNR) method is used to optimize the IRS phase shift matrix, which is called Max-SR-SLNR. Here, Eve is maximally interfered by transmitting artificial noise (AN) along the direct path and null-space projection (NSP) on the remaining two channels. To reduce the computational complexity, the CM, AN beamforming and IRS phase shift design are independently designed in the following methods. The CM beamforming vector is constructed based on maximum ratio transmission (MRT) criteria along the channel from Alice-to-IRS, and phase shift matrix of IRS is directly given by phase alignment (PA) method. This method is called MRT-NSP-PA. Simulation results show that the SR performance of the Max-SR-SLNR method outperforms the MRT-NSP-PA method in the cases of small-scale and medium-scale IRSs, and the latter approaches the former in performance as IRS tends to lager-scale.

翻译：作为协助通信的极好工具,智能反射表面(IRS)可以扩大覆盖范围,去除盲区,并实现惊人的速率改善。在本文件中,我们用IRS改进方向调制(DM)网络的机密率(SR)性能。为了充分探索IRS的好处,建议了两种有效的方法来提高IRS的效益。第一种方法是通过最大限度地提高SR来计算机密信息(CM)波形矢量成像矢量,并使用信号对泄漏传动比率(SLNR)方法来优化IRS阶段转换矩阵,称为Max-SR-SLNR。在这里,夏娃通过在直接路径上传播人工噪音(AN)和其余两个渠道的无空间投射(NSP)来最大程度地干预。为了降低计算复杂性,CMM、AN波形成像和IRS的阶段改变矢量向矢量转换(MS-S-SBA)方法以最高比率传输标准为基础,在IRS-IRS-S-SLSL的中,S-S-SLS-S-S-SLS-SLS-S-SLSBSLS-S-S-S-S-S-SL-SL-S-S-SL-SL-SL-SL-SL-SL-SL-SL-SL-SL-S-S-S-S-SB-S-S-S-S-S-S-SL-SL-S-S-S-SL-S-S-S-SL-SL-S-SL-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-SL-SL-SL-SL-SL-S-SL-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S</s>