Outdoor experiments on 5G radio access using distributed MIMO and beamforming in 28-GHz frequency band

This paper presents outdoor field experimental results that clarify 4-by-8 multiple-input multiple-output (MIMO) in the downlink throughput performance when applying distributed MIMO in the 28 GHz frequency band of a 5G cellular radio access system. A variety of transmission point (TP) deployments with narrow antenna beam forming is evaluated in order to investigate the downlink and uplink throughput performance and appropriate TP deployment for distributed MIMO. The experimental results show that the throughput is limited to approximately 7 Gbps in the downlink and 1 Gbps in the uplink in a parking area with localized MIMO. A distributed MIMO throughput gain is achieved with various TP deployments for both the downlink and uplink using two radio units. The outdoor parking area is an open space and multipaths are not anticipated, so a distinct advantage from distributed MIMO is expected. The distributed MIMO gain of 60% in the downlink and from 50 to 200% in the uplink is achieved at the cumulative distribution function of 80%. As a result of implementing distributed MIMO, throughput exceeding 10 Gbps in the downlink and 1.9 Gpbs in the uplink is achieved in the 28-GHz frequency band.