Although the fifth-generation (5G) networks are deployed at millimeter-wave (mmWave) frequencies, little information about the multipath clustering statistics for mmWave outdoor-to-indoor (O2I) propagation has been reported. This letter attempts to overcome this deficiency somewhat by investigating cluster-based propagation statistics for mmWave O2I that are based upon measurements. The measurements were conducted at 32 GHz at two office buildings. The multipath components (MPCs) were resolved by the space-alternating generalized expectation-maximization algorithm and the MPC clustering was performed by the K-power-means algorithm. We observed that numerous reflections bouncing back-and-forth between the windows cause large numbers of clusters. Other statistics such as the number of rays per clusters, cluster power and shadowing, cluster delay, and angular spread were also calculated.

中文翻译：

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基于 32-GHz 测量分析的基于集群的毫米波室外到室内传播特性

尽管第五代 (5G) 网络部署在毫米波 (mmWave) 频率上，但关于毫米波室外到室内 (O2I) 传播的多径聚类统计信息的报道很少。这封信试图通过调查基于测量的毫米波 O2I 的基于集群的传播统计数据来在一定程度上克服这一缺陷。测量是在两座办公楼以 32 GHz 频率进行的。多径分量 (MPC) 由空间交替广义期望最大化算法解决，MPC 聚类由 K-power-means 算法执行。我们观察到在窗口之间来回反射的大量反射会导致大量的簇。其他统计数据，例如每个簇的射线数、簇功率和阴影、簇延迟、