Linear and decision feedback equalizations for space-time block coded systems in frequency selective fading channels

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