This paper investigates the problem of improving security at the physical layer of a Millimeter Wave (mmWave) network equipped with multiple Intelligent Reflecting Surfaces (IRSs). In this network, the IRSs help the Base Station (BS) in transmitting its signal to the desired user and at the same time improving the physical layer security of the network by preventing the signal to be received by an illegitimate eavesdropper. The target of the proposed scheme is to maximize the secrecy rate by jointly optimizing the active beamforming at the BS and passive beamforming at the IRSs. This is done through a non-convex optimization problem which is solved by decomposing into two sub-problems. The sub-problems are alternatively solved using the Semi-Definite Relaxation (SDR) technique. Finally, simulations are done to assess the performance of the proposed algorithm. These results show the superiority of using multiple IRSs in the enhancement of secrecy rate of the wireless networks in the mmWave frequency bands.

本文研究了在配备多个智能反射面 (IRS) 的毫米波 (mmWave) 网络的物理层提高安全性的问题。在该网络中，IRS 帮助基站 (BS) 将其信号传输到所需用户，同时通过防止信号被非法窃听者接收来提高网络的物理层安全性。所提出方案的目标是通过联合优化 BS 的有源波束成形和 IRS 的无源波束成形来最大化保密率。这是通过非凸优化问题完成的，该问题通过分解为两个子问题来解决。子问题也可以使用半确定松弛 (SDR) 技术来解决。最后，进行仿真以评估所提出算法的性能。这些结果显示了使用多个 IRS 在增强毫米波频段无线网络保密率方面的优势。