Efficient space-time block codes designed by a genetic algorithm

Space-time block codes with orthogonal structures typically provide full-diversity reception and simple receiver processing. However, rate-1 orthogonal codes for complex constellations have not been found for more than two transmit antennas. By using a genetic algorithm, rate-1 space-time block codes that accommodate very simple receiver processing at the cost of reduced diversity are designed. Simulation results show that when the spectral efficiency is specified and an efficient outer code is used, the evolved codes provide better performance over the Rayleigh fading channel than minimum-decoding-complexity quasi-orthogonal space-time block codes at typical operating signal-to-noise ratios. When the fading is more severe than Rayleigh fading, evolved codes outperform orthogonal space-time block codes.