Compensation scheme for nonlinear distortion in OFDM systems

This paper presents an adaptive predistorter to compensate nonlinear distortion introduced by the high power amplifier (HPA) in OFDM systems. OFDM systems are susceptible to HPA nonlinearities in particular because of their large peak-to-average power ratios. In contrast to earlier work, the adaptive predistorter in this paper is based on both the direct and indirect learning architectures, and utilizes a complex Volterra series which is known to be suitable for compensating nonlinear phenomena. It is shown that the new predistorter scheme exhibits faster convergence than the previous method based on the indirect learning architecture only. In addition, the performance of the predistorter for OFDM systems is evaluated in terms of total degradation, optimal output backoff, and BER.