Channel estimation and equalization for space-time block coded systems in frequency selective fading channels

As an effective technique to combat adverse effects of fading, provide diversity and increase transmission rate, space-time coding (STC) has been gaining more and more attention recently. This paper presents efficient zero-forcing (ZF) and minimum mean-square error (MMSE) equalization schemes to combat intersymbol interference (ISI) and obtain diversity gain in a system using symbol-level spacetime block coding. General linear and decision feedback equalizers are derived with two transmit antennas and M receive antennas. The conditions are explored under which FIR channels can be equalized perfectly in noise-free environments. In order to estimate the system performance, upper bounds of bit error rate (BER) are derived. A training-aided method are proposed as well to estimate the channel state information (CSI) utilizing training sequences. Numerical results of the proposed techniques show significant performance improvement compared to the case without equalization, and show the tightness of the upper bounds along with the effectiveness of the channel estimation scheme.