Koshiro Kitao

The super-high-frequency (SHF) band is used in the 5th generation mobile communication system (5G), and the introduction of massive multiple-input multiple-output (MIMO) to 5G is being considered. In an environment with substantial propagation loss, such as that in the case of millimeter waves, massive MIMO can realize beamforming according to the position of terminal stations. Therefore, it is important to understand the direction of arrival of millimeter waves. In this paper, we clarify the relationship between power, delay time, and direction of arrival, while focusing on the horizontal direction, using a 48-element massive array in the 20-GHz band in urban Japan. In addition, we obtain direction of arrival estimation results using an iterative reduction threshold algorithm (ISTA), which is based on compressed sensing. It is shown that the dominant path can be estimated by using the ISTA even with approximately five elements.

We propose a correction formula using the percentage of area occupied by buildings, alpha, for a path model in the urban macrocell environment defined in ITU-R M.2135 based on measurements performed in Japan for below 6 GHz for 5G. Based on analysis, the regression results of the correction formula in which S, the median of the difference between the measured path loss and that of the reference path model is proportional to alpha, is better than when S is proportional to the logarithm of alpha.