We investigate the importance of weak clusters when modeling a wireless massive MIMO channel. We do this by studying the influence of densely spaced terminals and the number of base-station antennas for a zero-forcing precoded massive MIMO system. In particular, we focus on the influence on the correlation and imbalance between the signals at the terminal antennas, the effective channel-gain, the eigenvalue distributions and the number of clusters. The study is based on measured radio-channels from terminal prototypes with integrated antennas connected to a massive MIMO testbed. We further evaluate the advantage of using block-diagonalized zero-forcing compared to conventional zero-forcing in a massive MIMO system. Unexpectedly, terminals with low antenna envelope correlation coefficient may benefit significantly from block-diagonal zero-forcing in a massive MIMO system. The main conclusion is that weaker clusters are important when modeling multi-user scenarios.

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大规模MIMO系统中多用户对有效信道影响的案例研究

我们研究了在无线大规模 MIMO 信道建模时弱集群的重要性。我们通过研究密集间隔终端和基站天线数量对迫零预编码大规模 MIMO 系统的影响来实现这一点。我们特别关注终端天线信号之间的相关性和不平衡性、有效信道增益、特征值分布和簇数的影响。该研究基于来自终端原型的测量无线电信道，其中集成天线连接到大规模 MIMO 测试台。我们进一步评估了在大规模 MIMO 系统中使用块对角化迫零与传统迫零相比的优势。不料，具有低天线包络相关系数的终端可能会从大规模 MIMO 系统中的块对角迫零中受益。主要结论是，在对多用户场景建模时，较弱的集群很重要。