Quasi-Orthogonal Time-Reversal Space-Time Block Coding for Frequency-Selective Fading Channels

Quasi-orthogonal space–time block codes (QO-STBCs) are a powerful code family designed for more than two transmit antennas. In contrast to their orthogonal counterparts designed for the same number of transmit antennas, QO-STBCs are able to provide full-rate transmission rate. While original QO-STBCs enjoy only a partial diversity, the recently proposed rotated versions of QO-STBCs achieve the maximum diversity order which is equal to the number of transmit antennas. Since QO-STBCs have been originally proposed for frequency-flat fading channels, it is a challenging design problem to apply them over frequency-selective channels. The dispersive nature of such channels results in intersymbol interference which needs to be carefully handled at the receiver. In this paper, we investigate time-domain equalization for QO-STBC, exploiting the embedded quasi-orthogonal structure to design low-complexity receivers. We also present diversity gains for the proposed scheme through pairwise error probability (PEP) derivation and analysis which are further confirmed by Monte Carlo simulations.