Indoor and Outdoor Experiments on 5G Radio Access Using Distributed MIMO and Beamforming with a Variety of TP Deployments

This paper presents indoor and outdoor field experimental results that clarify 4-by-8 multiple-input multiple-output (MIMO) downlink throughput performance applying distributed MIMO with a variety of transmission point (TP) deployments and narrow antenna beam tracking in the 15 GHz frequency band of a 5G cellular radio access system in order to investigate the appropriate TP deployment for distributed MIMO. Experimental results show that a throughput gain from distributed MIMO is achieved in various TP deployments in the lobby of an office building and an outdoor parking area using two radio units (RUs). In the lobby, a deployment where TP #1 covers the entire lobby and TP #2 covers areas around TP #1 that are non-line-of-sight exhibits a significant advantage over when distributed MIMO is not used yielding a throughput gain of 11 % over most of the area. In the outdoor parking area, a distinct advantage when using distributed MIMO is expected, and a gain in throughput of 124 % is achieved when TPs face the same direction and have a large separation between them over when distributed MIMO is not used. However, a large difference in the mobility reference signal received power (MRSRP) is also confirmed, especially in front of the TPs due to the large difference in the distance between the mobile station and the TPs. We find that if the second TP has a signal power below 14 dB of the first TP's signal, it does not contribute to the MIMO transmission. In order to compensate for the difference in MRSRP, four RUs are installed in the parking area, and the distributed MIMO gain of 77 % is achieved.