5G Radio Access Experiments on Distributed MIMO Deployment for Straightly Traveling Mobile Station with Beamforming in 28-GHz Frequency Band

This paper focuses on a design for a base station (BS) antenna deployment targeting a mobile station (MS) traveling in a straight line assuming application to 5G systems for railways or vehicles. We present experimental results of outdoor measurements under line of sight (LoS) conditions showing 4-by-8 multiple-input multiple-output (MIMO) throughput performance when applying distributed MIMO with narrow antenna beam tracking in a 28-GHz frequency band in the downlink of a 5G cellular radio access system. To clarify a suitable deployment for a MS traveling along a straight line, two deployment cases are tested in which three BSs are used. One is a case where all transmission points (TPs) are arranged along the moving path of the MS, and the other is a case where two of the three TPs are on each side of the moving path. The experiments, in which the MS is installed on an electric trolley, reveal that the former deployment case has a trade-off relationship between the peak throughput and range. This relationship yields a higher peak throughput for a decrease in the TP separation distance. In contrast, the latter deployment case achieves both a high peak data rate and better throughput performance over the entirety of the traveling path compared to the former case, and exhibits the peak throughput value of 15 Gbps, which is almost the system peak value.