毫米波大规模多输入多输出（MIMO）系统可以带来频谱效率和能量效率数个量级的提升。但是由于硬件成本和能耗的限制，传统的每个天线元件需要一条射频链路的全数字波束成形技术不再可行。为解决这个问题，考虑采用部分连接的数模混合波束成形架构，提出一种联合设计基站（BS）端和用户端波束成形矩阵的方案。为了充分利用大规模MIMO系统的阵列增益，提出基于稀疏主成分分析的算法来获得相应的BS端模拟预编码和用户端模拟接收矩阵。然后，从最小化系统加权均方误差角度，提出迭代算法以联合优化数字预编码和接收矩阵。经过仿真验证，本文所提方案频谱效率接近现有的全连接混合波束成形架构的方案，而系统能耗大幅降低。
Millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems can achieve several orders of magnitude improvement in spectral efficiency and energy efficiency. However, due to limitations of hardware complexity and energy cost, the conventional fully digital beamforming methods which require one radio frequency chain per antenna element are no longer viable. To address this challenge, hybrid digital and analog beamforming architectures are proposed. In this paper, we consider the practical partially-connected hybrid beamforming structure and propose to jointly design the hybrid beamformers of both the base station and the users for a multi-user massive MIMO system. For the purpose of achieving a high array gain, a sparse principal component analysis based algorithm is utilized to obtain the corresponding analog precoding and combining matrices. Then we develop an iterative algorithm to jointly design the digital precoding and combining matrices under a weighted minimum mean square error criteria. Simulations over mmWave channels demonstrate that our scheme can approach the performance of those with fully-connected structures, with rather high energy efficiency.
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