相干多径环境下的毫米波大规模MIMO混合波束赋形方案

针对传统全数字域的解相干算法无法直接运用于混合波束赋形场景的问题，设计了一种混合波束赋形下的解相干方案。在模拟域，基于设计的码本波束，提出一种新的模拟波束赋形方案，分别搜索与每个信号方向最为接近的波束，形成波束集合，利用所得到的波束集合，对阵列接收信号分别进行模拟波束赋形得到一级输出。在数字域，提出“阵列信号重构”的思想，对一级输出进行阵列信号重构，将重构信号作为输入，进行空间平滑处理，在相干干扰方向和非相干干扰方向均可形成较深的“零陷”。通过理论分析和仿真，对不同方案的波束方向图、信干噪比、频谱效率等性能进行了研究。结果表明，所提出的混合波束赋形方案的信干噪比和频谱效率等性能几乎逼近于纯数字波束赋形方案。

Hybrid beamforming scheme for millimeter wave massive MIMO system in coherent multipath environment

The traditional full digital decoherence algorithm cannot be applied to hybrid beamforming. To solve the problem, a decoherence scheme for hybrid beamforming is proposed. In analog domain, based on designed codebook beams, a novel analog beamforming scheme is proposed. At first, the beams nearest to each signal direction are searched respectively, and a beam set is obtained. Next, utilizing the obtained beam set, the array received signals are analog-beamformed to obtain the output. In digital domain, the idea of "array signal reconstruction" is proposed and the output signals are reconstructed according to the array model at the first stage. At the second stage, the digital beamformer utilizes the reconstructed signals to perform spatial-smoothing algorithm, and deep "nulls" in the directions of both coherent and incoherent interferences can be formed. Through theoretical analysis and simulation, the performance of beam patterns, signal-to-interference-plus-noise-ratio (SINR) and spectral efficiency (SE) in different schemes are studied, and results show that SINR and SE of the proposed scheme are close to those of the full digital beamforming scheme.