Performance and implementation of a novel space-time block coded OFDM system

In multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, each low-rate signal is transmitted at different subcarriers and different antennas. Because the wide band frequency-selective fading channel is divided into multiple parallel narrow band flat-fading channels, there are different effects to the transmitted signals on each subcarrier owing to the frequency-selective fading property. This will cause the performance of signals transmitted over the tones that are in deep fading to become worse. Thus, we propose a design of space-time block codes based on spread frequency coding in this paper. The proposed scheme can exploit the inherent frequency diversity of the frequency-selective channels and improve the performance of MIMO OFDM systems.