Nonlinear Channel Characterization in OFDM Systems Using Signals With Spectral Notches

The authors consider the problem of characterizing nonlinear channels in real baseband OFDM communication systems. A novel method is proposed to estimate the frequency domain Volterra kernels of nonlinear channels using OFDM signals with spectral notches. In this method, the OFDM signal is arranged in a way that each full-spectral OFDM symbol frame is followed by copies of the same OFDM symbol frame but each has a spectral notch at a distinct frequency. They derive the mathematical expression of the difference signal between the outputs of a full-spectral OFDM symbol frame and its corresponding OFDM symbol frame with a spectral notch.