DFT-based decision directed channel estimation for OFDM systems in very large delay spread channels

In this paper, enhanced DFT-based channel estimation for OFDM system is proposed. Conventional DFT-based channel estimations improve the performance by suppressing time-domain noise. However, the disadvantage is that it cannot distinguish each path from the aliasing components of CIR when the periodic replicas of the estimated CIR are overlapped each other in very large delay spread channels. If any wrong CIR is chosen to obtain the CFR, a significant estimation error floor will appear despite of no ISI. In order to overcome the disadvantage, we consider a modified DFT-based channel estimation using decision-directed scheme. By using computer simulation, we show that proposed algorithm outperforms the conventional DFT-based estimation in terms of BER and MSE performance and displays sufficiently good performance similar to ideal case which is known CFR perfectly when the delay spread of multi-path channel is relatively large.