A model for performance evaluation in M-QAM-OFDM schemes in prescence of nonlinear distortions

The paper presents a model for a semi-analytic performance evaluation in M-QAM-orthogonal frequency division multiplexing (OFDM) digital radio systems in the presence of an additive white gaussian noise (AWGN) transmission channel and nonlinear distortions due to a high power amplifier (HPA). It is shown that, in the case of an OFDM system with a large number of sub-carriers, the distortion on the received symbol caused by the amplifier can be modelled, with negligible error, as a "Gaussian nonlinear noise" added to the received symbol. Considering this important remark the semi-analytical approach is only used to estimate means and variances of the "nonlinear noise" while these estimated parameters are subsequently used to evaluate the system bit error rate (BER) in a closed form. The advantage of this proposed method is that it strongly reduces the computational time. The proposed procedure is applied to evaluate M-QAM-OFDM performance in presence of nonlinear distortions due to high power amplifiers.