Interference Suppression for Block Diagonalization MIMO Downlink Systems over Time-Varying Channels

Kai ZHANG  Zhisheng NIU  

IEICE TRANSACTIONS on Communications   Vol.E90-B    No.12    pp.3687-3690
Publication Date: 2007/12/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.12.3687
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
multiuser MIMO,  time-varying channels,  time division duplex (TDD),  

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The performance of multiuser MIMO downlink systems with block diagonalization (BD) relies on the channel state information (CSI) at the transmitter to a great extent. For time division duplex TDD systems, the transmitter estimates the CSI while receiving data at current time slot and then uses the CSI to transmit at the next time slot. When the wireless channel is time-varying, the CSI for transmission is imperfect due to the time delay between the estimation of the channel and the transmission of the data and severely degrades the system performance. In this paper, we propose a linear method to suppress the interferences among users and data streams caused by imperfect CSI at transmitter. The transmitter first sends pilot signals through a linear spatial precoding matrix so as to make possible that the receiver can estimate CSI of other users, and then the receiver exploits a linear prefilter to suppress the interference. The numerical results show that the proposed schemes achieve obvious performance enhancement in comparison to the BD scheme with imperfect CSI at the transmitter.