Mutual information of OFDM systems with nonlinear power amplifier

Per subcarrier mutual information (MI) of OFDM with nonlinear power amplifier is found as a function of backoff (BO) for low and high Peak-SNR values. The proposed method gives close formula to calculate the exact value of MI without any assumption on distortions. Unfortunately, the calculation has exponential complexity. It is shown that exist low complexity approach which results with approximated MI but with controlled accuracy. As known the OFDM based communication has high spectral efficiency, but at the same time has also high peak to average power ratio. As a result the nonlinear power amplifier is driven with high BO to avoid non-linear distortions. We show that such strategy is not optimal and we find optimal BO to obtain maximum MI.