An Enhanced DSTTD-OFDM System with Decision-Feedback Detection

This paper presents a new double space-time transmit diversity-orthogonal frequency division multiplexing (DSTTD-OFDM) scheme using the zero-forcing decision-feedback (ZF-DF) detector. To improve the diversity gain of streams in the lower Alamouti´s STTD unit, the proposed system adopts frequency-repetition method. Analytical results verify that the proposed system can obtain the fourth order diversity gain, whereas the conventional DSTTD-OFDM system produces the second order diversity gain. We also suggest open-loop power allocation to minimize lower performance bound. Simulation results show that the proposed system outperforms the conventional DSTTD-OFDM system with the ZF-DF detector by about 3.7 dB at the bit error rate (BER) of 10 4. The open-loop power allocation provides additional 1.0 dB performance improvement.