This paper presents an empirical study of the uplink and downlink azimuth angle of arrival (AoA) in an urban micro (UMi) scenario at 28 GHz. At present, most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity. Although the channel correlation coefficient of the uplink and downlink can be as high as 0.8, this does not mean that they are the same. Only a real uplink measurement can accurately describe its channel conditions, and this is what this study does. A receiver equipped with a rotatable horn antenna is mounted at the base station and the user terminal, respectively, in simulating the uplink and downlink. To improve the angular resolution, we extract the multipath components (MPCs) using the space-alternating generalized expectation-maximization algorithm. Also, a spatial lobe approach is used to cluster the MPCs in the power angular spectrum. By matching MPCs with objects in the environment, we find that direct propagation and first-order reflections are dominant in line-of-sight and non-line-of-sight cases. By comparing our measurement with those in standard channel models, we verify that the AoA of clusters follows a Gaussian distribution in the uplink and downlink. In addition, a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.

本文提出了在28 GHz的城市微（UMi）场景中上行和下行方位角到达角（AoA）的实证研究。目前，大多数UMi测量在下行链路中进行，然后假设信道互易性来推断上行链路情况。尽管上行链路和下行链路的信道相关系数可以高达0.8，但这并不意味着它们相同。只有真实的上行链路测量才能准确描述其信道状况，这就是本研究所做的。在模拟上行链路和下行链路时，分别在基站和用户终端处安装有配备有可旋转喇叭天线的接收机。为了提高角度分辨率，我们使用空间替代广义期望最大化算法提取多径分量（MPC）。还，使用空间波瓣方法将MPC聚类在功率角谱中。通过将MPC与环境中的物体进行匹配，我们发现在视线和非视线情况下，直接传播和一阶反射占主导地位。通过将我们的测量结果与标准信道模型中的测量结果进行比较，我们可以验证集群的AoA在上行链路和下行链路中均遵循高斯分布。另外，建立了射线AoA和能量的二维高斯分布，以反映它们的相关性。我们验证了群集的AoA在上行链路和下行链路中均遵循高斯分布。另外，建立了射线AoA和能量的二维高斯分布，以反映它们的相关性。我们验证了群集的AoA在上行链路和下行链路中均遵循高斯分布。另外，建立了射线AoA和能量的二维高斯分布，以反映它们的相关性。