Experimental Verification of Null-Space Expansion for Multiuser Massive MIMO via Channel State Information Measurement

Tatsuhiko IWAKUNI  Kazuki MARUTA  Atsushi OHTA  Yushi SHIRATO  Masataka IIZUKA  

IEICE TRANSACTIONS on Communications   Vol.E101-B   No.3   pp.877-884
Publication Date: 2018/03/01
Online ISSN: 1745-1345
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
massive MIMO,  multiuser MIMO,  null-space expansion,  channel time variation,  inter-user interference,  

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This paper presents experimental results of our proposed null-space expansion scheme for multiuser massive multiple-input multiple-output (MIMO) in time varying channels. Multiuser MIMO transmission with the proposed scheme can suppress the inter-user interference (IUI) caused by outdated channel state information (CSI). The excess degrees of freedom (DoFs) of massive MIMO is exploited to perform additional null-steering using past estimated CSI. The signal-to-interference power ratio (SIR) and spectral efficiency performances achieved by the proposed scheme that uses measured CSI is experimentally evaluated. It is confirmed that the proposed scheme shows performance superior to the conventional channel prediction scheme. In addition, IUI can be stably suppressed even in high mobility environments by further increasing the null-space dimension.