Combining transmit beamforming, space-time block coding and delay spread reduction

Multipath fading and inter-symbol interference (ISI) are two fundamental impairments limiting the transmission quality of broadband wireless communications. In this paper we consider multiple-input single-output ISI channels and propose an ISI minimizing method implemented at the base station (BS) side using space time block coding (STBC) and statistical pre-filtering (SPF), which combines transmit beamforming (TB) with signal pre-alignment (PAL) based on the statistical knowledge of downlink channel state information (CSI). The proposed method transforms a time-dispersive channel into multiple flat fading channels, thus not only the ISI is minimized through SPF, but also the path diversity is maintained through STBC. With the delay spread reduction capability, the SPF method is further applied to multicarrier systems to reduce the cyclic prefix length, thus to increase the system throughput. Computer simulations have evaluated the effectiveness of the proposed method.