Hybrid-ARQ scheme employing different space-time trellis codes in slow fading channels

We consider a hybrid automatic repeat-request (ARQ) scheme employing different space-time trellis codes. In general, most design criteria for space-time trellis codes focus on minimizing the maximum pairwise error probability. However, in slow fading channels, since the maximum pairwise error probability differs little from other pairwise error probabilities, proper design techniques have to consider some pairwise error probabilities. We propose the measure of coding gain as performance measure. By using the proposed measure of coding gain, the optimal space-time trellis codes for each transmission are obtained through computer search. Simulation results show that hybrid-ARQ scheme consisting of the optimal space-time trellis codes for each transmission outperforms the hybrid-ARQ scheme consisting of the same space-time trellis codes for all transmission.