Performance of Iterative Decision Feedback Channel Estimation in Turbo FDE for DFT-Spread OFDM

This paper proposes iterative decision feedback channel estimation (IDFCE) using a time-division multiplexing based reference signal that is incorporated into a turbo frequency domain equalizer (FDE) for discrete Fourier transform (DFT)-Spread Orthogonal Frequency Division Multiplexing (OFDM) (DFT-S-OFDM hereafter). In the proposed IDFCE, estimated channel responses, which are used for weights in feed-forward and decision-feedback FDEs, are iteratively updated multiple times at each iteration of the turbo FDE. We present the average block error rate (BLER) performance of IDFCE using weighted coherent averaging employing empirically optimized fixed weights and the 2-dimensional (2D) linear minimum mean square error (LMMSE) algorithm for the turbo FDE in DFT-S-OFDM. Computer simulation results indicate the best window size for the 2D LMMSE algorithm assuming the 9-path Extended Typical Urban (ETU) channel model and the maximum Doppler frequency of up to approximately 220 Hz. The computer simulations also show that the 2D LMMSE based IDFCE is effective in decreasing the required average received signal-to-noise power ratio (SNR) that satisfies the target average BLER for the turbo FDE in a frequency-selective Rayleigh fading channel with low-to-high maximum Doppler frequencies and a wide range of root mean square delay spread values for DFT-S-OFDM.