Robust MIMO-OFDM System for Frequency-Selective Mobile Wireless Channels

This paper presents a novel technique to enhance the robustness of space-frequency block coded (SFBC) orthogonal frequency-division multiplexing (OFDM) systems. The proposed system shapes the channel matrix of a frequency-selective fading channel into a piecewise flat fading over each block of two adjacent subcarriers. Analytical and simulation results show that the proposed scheme substantially outperforms the conventional SFBC in frequency-selective fading channels, which assumes that the channel parameters are equal over the duration of the codeword. Moreover, we demonstrate that the proposed system offers a superior performance in fast time-varying channels where the interference that results from the channel variations acts only as an additive noise. In addition to its superior performance, the proposed system has low computational complexity, because it is based on the short-block-length Walsh-Hadamard transform.