The Enhanced Decoding Method for QO-SFBC System in Frequency Selective Fading Channel Environment

In this paper, we propose an enhanced decoding method to improve the performance of the quasi orthogonal (QO)-space frequency block coding (SFBC) in frequency selective fading channel environment. Generally, QO-SFBC obtains full diversity gain with more than two transmit antennas by using the constellation rotation in flat fading channel. However, QO-SFBC provides less diversity gain in frequency selective fading channel, because the discrepancy of channel frequency responses (CFRs) at adjacent subcarriers causes additive interferences. Although the conventional method using the simple averaging scheme for all CFRs at adjacent subcarriers can be effective for mitigating interferences, it is not quite robust to variation of CFRs, especially in high Doppler frequency environments. Therefore, to achieve better diversity gain in frequency selective fading channel environment, the selective averaged QO-SFBC decoding method based on mathematical analysis considering each CFR of elements in QO-SFBC encoding block is proposed. By using computer simulation, we show that the proposed method can provide better performance compared with the conventional methods and verify that the proposed method is attractive and suitable for implementation with stable operation when frequency selectivity is high.