In this paper, we consider the transmit linear precoding problem for MIMO systems with discrete-constellation inputs. We assume that the receiver has perfect channel state information (CSI) and the transmitter only has partial CSI, namely, the channel covariance information. We first consider MIMO systems over frequency-flat fading channels. We design the optimal linear precoder based on direct maximization of mutual information over the MIMO channels with discrete-constellation inputs. It turns out that the optimal linear precoder is a non-diagonal non-unitary matrix. Then, we consider MIMO systems over frequency selective fading channels via extending our method to MIMO-OFDM systems. To keep reasonable computational complexity of solving the linear precoding matrix, we propose a sub-optimal approach to restrict the precoding matrix as a block-diagonal matrix. This approach has near-optimal performance when we integrate it with a properly chosen interleaver. Numerical examples show that for MIMO systems over frequency flat fading channels, our proposed optimal linear precoder enjoys 6-9 dB gain compared to the same system without linear precoder. For MIMO-OFDM systems, our reduced-complexity sub-optimal linear precoder captures 3-6 dB gain compared to the same system with no precoding. Moreover, for those MIMO systems employing a linear precoder designed based on Gaussian inputs with gap approximation technique for discrete-constellation inputs, significant loss may occur when the signal-to-noise ratio is larger than 0 dB.
C. Xiao and Y. R. Zheng, "Transmit Precoding for MIMO Systems with Partial CSI and Discrete-Constellation Inputs," Proceedings of the IEEE International Conference on Communications, 2009. ICC'09, Institute of Electrical and Electronics Engineers (IEEE), Jun 2009.
The definitive version is available at http://dx.doi.org/10.1109/ICC.2009.5199543
2009 IEEE International Conference on Communications (2009: June 14-18, Dresden)
Electrical and Computer Engineering
National Science Foundation (U.S.)
United States. Office of Naval Research
Keywords and Phrases
MIMO Channel; MIMO-OFDM Systems; Partial CSI; Precoding Matrix; Transmit Precoding
Article - Conference proceedings
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