Analysis of amplitude and phase predistortion and polynomial-based predistortion in OFDM systems

The major drawback of orthogonal frequency division multiplexing (OFDM) systems is the high peak to average power ratio (PAPR), which significantly limits the power efficiency of the operating power amplifier (PA) to avoid nonlinear distortions. Many predistortion techniques have been proposed to perform PA linearization to compensate nonlinear distortions to obtain higher amplifier efficiency. In this paper, we analyze the use of baseband predistorters in OFDM systems. Two PA models are considered: the traveling wave tube amplifier (TWTA) model and Wiener-Hammerstein model. Two types of predistorters are investigated: the amplitude and phase predistorter and polynomial-based predistorter with indirect learning architecture. A comparative study of performance of different combinations of PA models and predistorters is presented in terms of both total degradation (TD) and power spectral density (PSD). Simulation results show that both TD and PSD need to be jointly considered for performance evaluation in the development of the predistorter design.