Transmit diversity and equalization for frequency selective fading channels

As a coding technique designed for use with multiple transmit antennas, space-time coding (STC) has been gaining more attention recently due to its attractive characteristics to provide diversity at the receiver and coding gain over an uncoded system without sacrificing the bandwidth, and increase the effective transmission rate as well as the potential system capacity. This paper presents both minimum mean-square error (MMSE) and zero-forcing (ZF) equalization schemes to combat intersymbol interference (ISI) and obtain diversity gain in a system with the transmit diversity technique using space-time block coding. General linear equalizers are derived for the transmit diversity case with two transmit antennas and M receive antennas. We investigate the conditions under which FIR channels can be equalized perfectly using linear FIR filters in noise-free environments. A BPSK modulation scheme is assumed to simulate the proposed diversity and equalization methods. Numerical results show significant performance improvement compared to the case without equalization.