Abstract
This paper presents an empirical study of the and (AoA) in an urban micro (UMi) scenario at 28 GHz. At present, most UMi measurements are conducted in the and then the situation is inferred assuming channel reciprocity. Although the channel correlation coefficient of the and can be as high as 0.8, this does not mean that they are the same. Only a real 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 and . 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 and . In addition, a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.
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