Power Amplifier Effects and Peak-to-Average Power Mitigation

Multicarrier systems suffer from high Peak-to-Average Power Ratio (PAPR). If the High-Power Amplifier (HPA) is operated in its quasilinear region, the high PAPR of the multicarrier signal has no influence on the quality of the transmission. Nevertheless, this situation has a high cost in terms of energy efficiency, especially, for mobile applications with batteries. To increase power efficiency, High Power Amplifier (HPA) should be operated as close as possible to its saturation point, but this would introduce broadening of the amplified signal spectrum and a distortion over the transmitted signal itself. In this chapter, we review common HPA nonlinearity models and study the impairments in terms of in-band distortion and out-of-band spectral regrowth. Finally, we present how to mitigate nonlinearity effects by linearizing the HPA conversion characteristics through digital predistortion and/or by reducing the PAPR of the FBMC signal.