Spectral Analysis of a Nonlinear WOLA-OFDM System with DPD

Abstract

Orthogonal frequency division multiplexing (OFDM) has been a universal choice for modulation scheme for most of the wireless standards such as long-term evolution (LTE). However, OFDM is prone to large out-of-band (OOB) emission due to slower decay of its side-lobes. Weighted overlap and add OFDM (WOLA-OFDM) have been proposed for mitigating the out-of-band (OOB) emission by improving faster sidelobe decay. However, the presence of nonlinear high power amplifier (HPA) worsens the OOB performance of OFDM, even though the windowing reduces the noise floor considerably. In this work, we have proposed an architecture based on digital predistorter (DPD) to reduce the impact of non-linearity in WOLA-OFDM in the presence of HPA. The results show that the stated benefits of WOLA-OFDM can only be attained through employing DPD in the nonlinear WOLA-OFDM systems.