Recent Studies on Massive MIMO Technologies for 5G Evolution and 6G

A massive multiple-input multiple-output (M-MIMO) technology was introduced for 5G in millimeter-wave (mmW) bands such as 28 GHz. Further enhancement of 5G, socalled 5G Evolution (5GE) is expected to exploit advanced beamforming technologies and M-MIMO technologies combined with base station (BS) cooperation in order to achieve more stable and higher data-rate mmW transmission. For 6G, extremely high data rate exceeding 100 Gbps is required, and hence so-called sub-terahertz wave targeting the frequency from 100 GHz to 300 GHz has attracted much attention. This paper introduces our recent studies on M-MIMO technologies for 5GE and 6G. Concretely, it shows experimental results of M-MIMO BS cooperation technologies for mmW 5GE. For 6G, in link-level simulations using 100 GHz-band M-MIMO technology, over-100 Gbps downlink throughput and coverage performances are clarified. In addition, 100 GHz-band system-level performances are shown by our developed 6G simulator employing multiple M-MIMO BSs in a future shopping mall environment.