MIMO Precoding Effective for Path-Loss Imbalance and Antenna Correlation in Cooperative Base Station Systems

Yasuyuki HATAKAWA  Masashi FUSHIKI  Satoshi KONISHI  

IEICE TRANSACTIONS on Communications   Vol.E94-B   No.1   pp.243-252
Publication Date: 2011/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.243
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
cooperative base stations,  multiple input multiple output,  precoding,  log likelihood ratio,  

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This paper proposes a multiple-input multiple-output (MIMO) precoding scheme for the down link of single user (SU) cooperative base station (BS) systems. The proposed precoding scheme mitigates the performance degradation caused by large inter-BS path-loss imbalance and large intra-BS antenna correlation by controlling two parameters. The proposed precoding scheme multiplexes the multiple layers by adjusting the amplitude of each layer, and then decreases the occurrence probability of the small absolute value of the log likelihood ratio (LLR), and so reduces the bit error rate (BER). Link level simulation results show that the proposed precoding scheme decreases the required signal-to-noise ratio (SNR) of BER = 0.001 by 5.5 dB, 2.2 dB, and 0.7 dB in the case of QPSK and coding rate 1/1, 3/4, and 1/2 respectively. The proposed precoding scheme is also evaluated in terms of spectrum efficiency using rank adaptation and adaptive modulation, showing that it improves the spectrum efficiency when the SNR per a receiver antenna is higher than 4 dB.