As communication systems that employ millimeter wave (mmWave) frequency bands must use large antenna arrays to overcome the severe propagation loss of mmWave signals, hybrid beamforming has been considered as an integral component of mmWave communications. Recently, intelligent reflecting surface (IRS) has been proposed as an innovative technology that can significantly improve the performance of mmWave communication systems through the use of low-cost passive reflecting elements. In this paper, we study IRS-aided mmWave multiple-input multiple-output (MIMO) systems with hybrid beamforming architectures. We first exploit the sparse-scattering structure and large dimension of mmWave channels to develop the joint design of IRS reflection matrix and hybrid beamformer for narrowband MIMO systems. Then, we generalize the proposed joint design to broadband MIMO systems with orthogonal frequency division multiplexing (OFDM) modulation by leveraging the angular sparsity of frequency-selective mmWave channels. Simulation results demonstrate that the proposed joint designs can significantly enhance the spectral efficiency of the systems of interest and achieve superior performance over the existing designs.

中文翻译：

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用于智能反射面辅助毫米波 MIMO 系统的混合波束成形

由于采用毫米波（mmWave）频段的通信系统必须使用大型天线阵列来克服毫米波信号的严重传播损耗，因此混合波束成形已被视为毫米波通信的一个组成部分。最近，智能反射面（IRS）被提出作为一种创新技术，可以通过使用低成本的无源反射元件显着提高毫米波通信系统的性能。在本文中，我们研究了具有混合波束成形架构的 IRS 辅助毫米波多输入多输出 (MIMO) 系统。我们首先利用毫米波信道的稀疏散射结构和大尺寸来开发用于窄带 MIMO 系统的 IRS 反射矩阵和混合波束形成器的联合设计。然后，我们通过利用频率选择性毫米波信道的角度稀疏性，将提议的联合设计推广到具有正交频分复用 (OFDM) 调制的宽带 MIMO 系统。仿真结果表明，所提出的联合设计可以显着提高相关系统的频谱效率，并实现优于现有设计的性能。