Theoretical analysis of OFDM signals in nonlinear polynomial models

This paper presents a theoretical analysis of nonlinear distortion effects in an Orthogonal Frequency Division Multiplexing (OFDM) system when the signal is passed through a nonlinear high power amplifier (HPA) which is modeled as a nonlinear polynomial model. From theoretical analysis of the received OFDM signal it is shown that the data symbol detected after the decision device at the receiver comprises of complex phase shifted version of the original transmitted data symbol as well as Inter Carrier Interference (ICI) components which can be modeled as a Gaussian nonlinear noise term uncorrelated with the data symbol. Analytical expressions for the complex phase shift and nonlinear noise term are derived. Thus from the derived expressions the output signal to noise ratio and hence probability of error can be evaluated theoretically, avoiding a need to perform extensive simulations. A comparison between the theoretical and simulated results are also presented to verify the accuracy of our analysis.