In this paper, we propose the hybrid-precoding design that alleviates the performance loss caused by beam-misalignment in the mmWave multi-user communication systems. To this end, we firstly design the beam-misalignment aware fully-digital precoders for two distinct scenarios. First, for a base-station (BS) with full estimated channel-state-information (CSI), the minimum-mean-squared-error metric incorporating the `error-statistics' of the beam-misalignment error is used to analytically derive a closed-form expression for the fully-digital precoder, which maximizes the array gain while suppressing the inter-user interference for each user-equipment (UE). Second, for a BS which can only acquire partial estimated CSI, a min-max non-convex optimization is considered to obtain the fully-digital precoder, which minimizes the maximum loss in the array gains of the expected beam-misalignment `error-range' over the UEs while cancelling the inter-user interference. Subsequently, we propose the hybrid-precoding design that approximates the fully-digital designs based on the gradient-projection method, which is mathematically proven to converge to an approximate local solution with further reduced complexity compared to the state-of-the-art algorithms. Finally, the proposed hybrid-precoding design is further extended to the wideband mmWave communication systems. Numerical results show that the proposed hybrid-precoding design can effectively alleviate the performance degradation incurred by the beam-misalignment.

中文翻译：

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存在波束未对准情况下的毫米波多用户通信的混合预编码


在本文中，我们提出了混合预编码设计，可以减轻毫米波多用户通信系统中波束失准造成的性能损失。为此，我们首先为两种不同的场景设计了波束失准感知的全数字预编码器。首先，对于具有完全估计的信道状态信息（CSI）的基站（BS），使用结合波束失准误差的“误差统计”的最小均方误差度量来分析导出全数字预编码器的封闭式表达式，可最大化阵列增益，同时抑制每个用户设备 (UE) 的用户间干扰。其次，对于只能获取部分估计CSI的BS，考虑最小-最大非凸优化以获得全数字预编码器，这最小化了预期波束失准误差范围的阵列增益的最大损失'同时消除用户间干扰。随后，我们提出了基于梯度投影方法的近似全数字设计的混合预编码设计，该设计在数学上被证明可以收敛到近似局部解，与最先进的算法相比，复杂度进一步降低。最后，所提出的混合预编码设计进一步扩展到宽带毫米波通信系统。数值结果表明，所提出的混合预编码设计可以有效减轻波束失准引起的性能下降。