A precoder based on the exact optimization of the minimum Euclidean distance d min between signal points at the receiver side is proposed for MIMO-OFDM systems using a 16-QAM modulation. Assuming that channel state information (CSI) can be made available at the transmitter, the channel is diagonalized and a precoder can be derived. A numerical approach shows that the precoder design depends on the channel characteristics, leading to 8 different precoder expressions. Comparisons with maximum signal-to-noise ratio (SNR) strategy and other precoders based on criteria, such as water-filling (WF), minimum mean square error (MMSE), and maximization of the minimum singular value of the global channel matrix, are performed to illustrate the significant bit-error-rate (BER) improvement of the proposed precoder. In order to make its implementation easier, it is shown that it can be expressed by only two ways without significant performance degradation.

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In this article, we investigate the linear precoder based on the maximization of the minimum Euclidean distance between two received data vectors. This new precoding matrix is expressed as the product of a power allocation matrix and an input-shaping matrix. The input-shaping matrix is selected as a normalized discrete Fourier transform-matrix, and the optimal power allocation depends on the channel characteristics. For each number of available datastreams, we propose a general form of the optimized precoding matrix. These forms are suitable for different transmit channels and especially for all rectangular quadrature amplitude modulation modulations. We show, in the simulation results, that the proposed precoder provides a significant improvement in terms of bit error rate performance compared to other traditional precoding strategies.