Millimeter wave (mmWave) communications have been considered as a key technology to enable very high data rate in the fifth-generation applications. Multiple-input-multiple-output (MIMO) systems with hardware efficient analog/digital hybrid beamformer architecture have been widely considered to overcome the severe propagation loss of the mmWave channels. However, physical layer security in the mmWave wiretap MIMO systems and secure hybrid beamformer design have not been well investigated. In this paper, we consider the problem of the hybrid beamformer design for the secure transmission in mmWave wiretap MIMO systems in order to protect the legitimate transmission from eavesdropping. We aim to develop efficient secure hybrid beamformer design algorithms for both codebook-free and codebook-based analog beamformer schemes with either high-resolution or low-resolution phase shifters. Particularly, when eavesdropper's channel state information (CSI) is known, we first propose a joint analog precoder and combiner design algorithm that can prevent the information leakage to the eavesdropper. Then, the digital precoder and combiner are computed based on the obtained effective baseband channel to further maximize the secrecy rate. If prior knowledge of the eavesdropper's CSI is unavailable, we develop an artificial-noise-based hybrid beamforming approach, which can disrupt eavesdropper's reception while maintaining the quality-of-service of the intended receiver at a prespecified level. Extensive simulation results validate the effectiveness of the proposed secure hybrid beamformer designs under different availabilities of eavesdroppers CSI.

中文翻译：

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mmWave MIMO窃听系统中的安全混合波束成形器设计

毫米波（mmWave）通信已被视为在第五代应用中实现极高数据速率的关键技术。具有硬件有效的模拟/数字混合波束形成器架构的多输入多输出（MIMO）系统已被广泛考虑，以克服mmWave信道的严重传播损耗。但是，mmWave窃听MIMO系统中的物理层安全性和安全的混合波束形成器设计尚未得到很好的研究。在本文中，我们考虑了mmWave窃听MIMO系统中用于安全传输的混合波束形成器设计问题，以保护合法传输不被窃听。我们旨在为具有高分辨率或低分辨率移相器的无码本和基于码本的模拟波束形成器方案开发高效的安全混合波束形成器设计算法。特别是，当已知窃听者的信道状态信息（CSI）时，我们首先提出一种联合模拟预编码器和组合器设计算法，可以防止信息泄漏到窃听者。然后，基于所获得的有效基带信道来计算数字预编码器和组合器，以进一步使保密率最大化。如果无法获得有关窃听者CSI的先验知识，我们将开发一种基于人工噪声的混合波束成形方法，该方法可以中断窃听器的接收，同时将预定接收器的服务质量保持在预定水平。