Transmission Systems Predistortion and nonlinear detection for OFDM signals in the presence of nonlinear high power amplification
In this paper we present and compare several methods of compensating the nonlinearity of the RF front-end of a wireless system. Two baseband compensation techniques, namely predistortion and postdistortion (equalization) of the baseband signal are discussed and the problems associated with each one is addressed. Furthermore a combination of a predistorter and a nonlinear equalizer and also predistortion of oversampled baseband signal are analyzed. It will be shown that under realistic conditions with a frequently saturated amplifier and ISI channel, the latter two methods are able to compensate the nonlinearity up to a good extent, while the first two methods can only operate under certain assumptions for channel conditions and nonlinearity type.