Wideband Digital Post-Distortion for Improved Power-Efficiency and Coverage in OFDMA Networks

Abstract

This paper introduces a novel digital post-distortion (DPoD) technique designed to improve the received signal quality in multi-user orthogonal frequency-division multiple access (OFDMA) systems under severe power amplifier (PA) nonlinearities in the involved transmitters. The proposed approach combines memory polynomial-based nonlinear distortion modeling and cancellation with practical parameter estimation using demodulation reference signals (DMRS). Importantly, a new extended DMRS structure and corresponding receiver signal processing solutions are proposed which enable the receiver to mitigate both the ordinary pass-band nonlinearities as well as nonlinear crosstalk or interference between multiple frequency-multiplexed transmitters operating simultaneously within the channel bandwidth. Extensive numerical evaluations conducted in a 5G NR uplink scenario at 28GHz demonstrate significant receiver performance improvements, measured through effective error vector magnitudes (EVMs) for the frequency-multiplexed waveforms. The results validate the method's effectiveness even under aggressive PA nonlinearities and high-order modulation schemes including 64-QAM and 256-QAM, thus paving the way towards improved power-efficiency and coverage in future OFDMA networks.