Space-Frequency Parallel Transmitter Diversity Techniques for Three Pre-Coded OFDM Systems

This brief presents three space-frequency (SF) precoded orthogonal frequency division multiplexing (OFDM) systems to combat inter-carrier interference in mobile fading channels without knowing the channel state information at the transmitter. First, a 2×1 SF architecture is developed to form a 2×1 SF-OFDM system. Second, the parallel cancellation scheme is integrated with this SF-OFDM system to form a new SFPC-OFDM system. Third, three orthogonal transforms, Walsh-Hadamard (WH), Haar, and Slant, are employed as the pre-coder to form WHSFPC-, HAARSFPC-, and SLANTSFPCOFDM systems. All three pre-coded systems improve bit error rate without expanding power or bandwidth in comparing with the SFPC scheme. Simulations indicate that both WHSFPC and SLANTSFPC-OFDM systems outperform both SFPC and HAARSFPC-OFDM systems, while SFPC-OFDM systems outperform SF-OFDM systems. All three pre-coded SFPC schemes are simple and backward compatible with the existing OFDM system. They may serve as baseband building blocks in OFDM transceivers and can be expanded to multiple input and multiple output systems.