Dwpt Based FFT and ITS Application to SNR Estimation in OFDM Systems

In this paper, wavelet packet (WP) based FFT and its application to SNR
estimation is proposed. OFDM systems demodulate data using FFT. The
proposed solution computes the exact FFT using WP and its computational
complexity is of the same order as FFT, i.e. O (N log2 N). SNR estimation is done
inside wavelet packet based FFT block unlike other SNR estimators which
perform SNR estimation after FFT. The data, so analyzed using wavelet packets,
is used to perform SNR estimation in colored noise. The proposed estimator
takes into consideration the different noise power levels of the colored noise over
the OFDM sub-carriers. The OFDM band is divided into several sub-bands using
wavelet packet and noise in each sub-band is considered white. The secondorder
statistics of the transmitted OFDM preamble are calculated in each subband
and the power of the noise is estimated. The proposed estimator is
compared with Reddy’s estimator for colored noise in terms of mean squared
error (MSE).