Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article A Diversity Guarantee and SNR Performance for Unitary Limited Feedback MIMO Systems | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2008 Article ID 594928 15 pages doi 2008 594928 Research Article A Diversity Guarantee and SNR Performance for Unitary Limited Feedback MIMO Systems Bishwarup Mondal and Robert W. Heath Jr. Department of Electrical and Computer Engineering The University of Texas at Austin University Station C0803 Austin TX 78712 USA Correspondence should be addressed to Robert W. Heath Jr. rheath@ Received 16 June 2007 Accepted 26 October 2007 Recommended by David Gesbert A multiple-input multiple-output MIMO wireless channel formed by antenna arrays at the transmitter and at the receiver offers high capacity and significant diversity. Linear precoding may be used along with spatial multiplexing SM or space-time block coding STBC to realize these gains with low-complexity receivers. In the absence of perfect channel knowledge at the transmitter the precoding matrices may be quantized at the receiver and informed to the transmitter using a feedback channel constituting a limited feedback system. This can possibly lead to a performance degradation both in terms of diversity and array gain due to the mismatch between the quantized precoder and the downlink channel. In this paper it is proven that if the feedback per channel realization is greater than a threshold then there is no loss of diversity due to quantization. The threshold is completely determined by the number of transmit antennas and the number of transmitted symbol streams. This result applies to both SM and STBC with unitary precoding and confirms some conjectures made about antenna subset selection with linear receivers. A closed form characterization of the loss in SNR transmit array gain due to precoder quantization is presented that applies to a precoded orthogonal STBC system and generalizes earlier results for single-stream beamforming. Copyright 2008 B. Mondal and R. W. Heath Jr. This is an open access .
