Comparative Performance Analysis of 6G Waveforms with High Power Amplifier Nonlinearities

Abstract

The evolution from LTE and 5G toward 6G wireless systems faces two fundamental challenges: reliable operation under extreme mobility and resilience against hardware impairments, particularly nonlinearities from high power amplifiers (HPAs). While LTE and 5G have successfully adopted CP-OFDM, this waveform suffers from high peak-to-average power ratio (PAPR) and poor spectral localization, limiting its suitability for future energy-efficient and spectrally agile deployments. Numerous prior studies have investigated individual advanced waveforms (WFs), but none has provided a complete comparative analysis that jointly considers high mobility and HPA nonlinearity. This paper presents a comprehensive comparative analysis of five advanced WFs GFDM, FBMC-OQAM, UFMC, OTFS, and AFDM under realistic high-mobility and nonlinear HPA conditions. Using a standardized urban microcell (UMi) millimeter-wave (FR2) channel at 28 GHz with user speeds up to 120 km/h, we evaluate key performance metrics: PAPR, power spectral density (PSD), adjacent channel power ratio (ACPR), and symbol error rate (SER). The HPA nonlinearity is modeled with a realistic modified Rapp model. Our results reveal that OTFS and AFDM consistently outperform the other WFs, offering superior robustness to both high Doppler shifts and HPA-induced distortions. To the best of our knowledge, this is the first study that combines these candidate WFs under the same realistic highmobility and hardware-impairment framework. These findings position OTFS and AFDM as compelling candidates for energy-efficient and hardware-resilient $mathrm{6G}$ physical layers, particularly in high-mobility scenarios such as vehicular and regional rail communications.