Channel Estimation Based on a Time-Domain Threshold for OFDM Systems

Channel estimation for OFDM systems is usually carried out in frequency domain by the least-squares (LS) method using known pilot symbols. The LS estimator has a merit of low complexity but may suffer from noise because it does not consider any noise effect in obtaining its solution. To enhance the noise immunity of the LS estimator, we consider the estimation noise in time domain named discrete Fourier transform (DFT)-based channel estimation. Residual noise existing at the estimated channel coefficients in time domain could be reduced by reasonable selection of a threshold value. To achieve this, we propose a channel-estimation method based on a time-domain threshold which is a standard deviation of noise obtained by wavelet decomposition. Computer simulation shows that the estimation performance of the proposed method approaches to that of the known-channel case in terms of bit-error rates after the Viterbi decoder in overall SNRs.