Hybrid precoding is essential for millimeter wave (mmWave) multiple-input multiple output (MIMO) systems due to its inherent advantage of a high gain, whilst alleviating the high cost of hardware. However, most of the existing literature considered either the narrowband or wideband single-user mmWave MIMO scenarios. Hence in this paper we focus our attention on the more challenging design of hybrid Transmit Precoding (TPC) for wideband multiuser mmWave MIMO systems by exploiting the long-term channel’s covariance matrix and the angle of departure (AoD) information. Specifically, in the analog TPC designed, firstly, the analog TPC matrix having an infinite angular resolution is constructed based on the channel’s covariance matrix. Then, we also propose a non-uniformly spaced quantization codebook based analog TPC having finite angular resolution. Furthermore, a phase compensation operation is carried out to alleviate the effect of beam squint. As for the design of the digital TPC, a two-stage scheme is proposed to cancel the inter-user interference and to attain multiplexing gains. We study the effects of various parameters on the achievable sum rate and demonstrate with the aid of our simulation results that the proposed hybrid TPC is capable of achieving a similar performance to the excessive-complexity fully digital TPC.

中文翻译：

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用于宽带多用户毫米波 MIMO 系统的信道协方差和出发角辅助混合预编码

混合预编码对于毫米波 (mmWave) 多输入多输出 (MIMO) 系统至关重要，因为它具有高增益的固有优势，同时可以减轻硬件的高成本。然而，大多数现有文献都考虑了窄带或宽带单用户毫米波 MIMO 场景。因此，在本文中，我们通过利用长期信道的协方差矩阵和偏离角 (AoD) 信息，将注意力集中在宽带多用户毫米波 MIMO 系统的混合传输预编码 (TPC) 更具挑战性的设计上。具体而言，在设计的模拟TPC中，首先基于信道的协方差矩阵构造具有无限角分辨率的模拟TPC矩阵。然后，我们还提出了一种基于非均匀间隔量化码本的具有有限角分辨率的模拟 TPC。此外，执行相位补偿操作以减轻光束斜视的影响。对于数字TPC的设计，提出了两级方案来消除用户间干扰并获得复用增益。我们研究了各种参数对可实现的总速率的影响，并借助我们的仿真结果证明了所提出的混合 TPC 能够实现与过度复杂的全数字 TPC 类似的性能。