Noise cancellation method for OFDM systems

Summary form only given. The orthogonal frequency division multiplexing (OFDM) signal is corrupted by a multipath channel and additive white Gaussian noise (AWGN). The OFDM system introduces a guard interval to avoid inter-symbol interference (ISI). However, an equalizer is required to compensate for fading distortion even if the delay of the multipath channel is shorter than the length of guard interval. The frequency domain equalizer is often used in OFDM systems. However, the estimation accuracy of channel response is degraded due to the AWGN. In order to solve the problem, a noise cancelling technique based on an adaptive digital filter is proposed. The OFDM signal is periodic with a period of fast Fourier transform (FFT). So, the current OFDM signal has high correlation with the signal shifted by a period of FFT. On the other hand, the current AWGN is not correlated with the AWGN shifted by a period of FFT. Therefore, the proposed system estimates only the OFDM signal, which is corrupted by the multipath channel, by taking advantage of the difference between autocorrelation of the OFDM signal and the AWGN.