Experimental Study of Large-Scale Coordinated Multi-User MIMO for 5G Ultra High-Density Distributed Antenna Systems

Takaharu KOBAYASHI  Masafumi TSUTSUI  Takashi DATEKI  Hiroyuki SEKI  Morihiko MINOWA  Chiyoshi AKIYAMA  Tatsuki OKUYAMA  Jun MASHINO  Satoshi SUYAMA  Yukihiko OKUMURA  

IEICE TRANSACTIONS on Communications   Vol.E102-B    No.8    pp.1390-1400
Publication Date: 2019/08/01
Publicized: 2019/02/20
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2018TTP0012
Type of Manuscript: Special Section PAPER (Special Section on Technology Trials and Proof-of-Concept Activities for 5G and Beyond)
5G,  cell densification,  distributed antenna system,  coordinated multi-user MIMO,  field experiment,  

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Fifth-generation mobile communication systems (5G) must offer significantly higher system capacity than 4G in order to accommodate the rapidly increasing mobile data traffic. Cell densification has been considered an effective way to increase system capacity. Unfortunately, each user equipment (UE) will be in line-of-sight to many more transmission points (TPs) and the resulting inter-cell interference will degrade system capacity. We propose large-scale coordinated multi-user multiple-input multiple-output (LSC-MU-MIMO), which combines MU-MIMO with joint transmission from all the TPs connected to a centralized baseband unit. We previously investigated the downlink performance of LSC-MU-MIMO by computer simulation and found that it can significantly reduce inter-TP interference and improve the system capacity of high-density small cells. In this paper, we investigate the throughput of LSC-MU-MIMO through an indoor trial where the number of coordinated TPs is up to sixteen by using an experimental system that can execute real-time channel estimation based on TDD reciprocity and real-time data transmission. To clarify the improvement in the system capacity of LSC-MU-MIMO, we compared the throughput measured in the same experimental area with and without coordinated transmission in 4-TP, 8-TP, and 16-TP configurations. The results show that with coordinated transmission the system capacity is almost directly proportional to the number of TPs.