A Virtual Layered Successive Detector with Adaptive Transmit Signal Phase Rotation for QAM

Satoshi DENNO  Jun IMAMURA  Masahiro MORIKURA  

IEICE TRANSACTIONS on Communications   Vol.E95-B   No.10   pp.3232-3241
Publication Date: 2012/10/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E95.B.3232
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
MIMO,  spatial multiplexing,  QAM,  virtual channel,  successive detection,  eigenvalue,  

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This paper proposes a virtual layered successive detector with adaptive transmit signal phase rotation for quadrature amplitude modulation (QAM) that enables high speed communication even in downlinks of wireless communication systems. It is shown that the detection performance is degraded when the eigenvalue of a virtual channel becomes close to the power of the additive white Gaussian noise (AWGN). Therefore, adaptive transmit signal phase rotation is introduced for the detector to improve the transmission performance. For the transmit phase rotation, three techniques to search the rotation angles are proposed, which can reduce the feedback information from the receiver to the transmitter. Among the three proposed techniques, the technique called “iterative variable step step search” is shown to achieve the best performance. Actually, it is confirmed by computer simulation that the variable step search makes the detector attain about 17 dB of a gain at the bit error rate (BER) of 10-5 in 42 multiple-input-multiple-output (MIMO) systems.