Performance Of Open-Loop Transmit Diversity With Intra-Subframe Frequency Hopping And Iterative Decision-Feedback Channel Estimation For Dft-Precoded Ofdma

Open-loop (OL) transmit diversity is more subject to the influence of channel estimation error than closed-loop (CL) transmit diversity, although it has the merit of providing better performance in fast Doppler frequency environments because it doesn't require a feedback signal. This paper proposes an OL transmit diversity scheme combined with intra-subframe frequency hopping (FH) and iterative decision-feedback channel estimation (DFCE) in a shared channel for discrete Fourier transform (DFT)-precoded orthogonal frequency division multiple access (OFDMA). We apply intra-subframe FH to OL transmit diversity to mitigate the reduction in the diversity gain under high fading correlation conditions among antennas and iterative DFCE to improve the channel estimation accuracy. Computer simulation results show that the required average received signal-to-noise power ratio at the average block error rate (BLER) of 10(-2) of the space-time block code (STBC) with intra-subframe FH is reduced to within approximately 0.8 dB compared to codebook-based CL transmit diversity when using iterative DFCE at the maximum Doppler frequency of f(D) = 5.55 Hz. Moreover, it is shown that STBC with intra-subframe FH and iterative DFCE achieves much better BLER performance compared to CL transmit diversity when f(D) is higher than approximately 30 Hz since the tracking ability of the latter degrades due to the fast fading variation in its feedback loop.