PAPR reduction and digital predistortion for 5G waveforms in digital satellite payloads

Satellite systems will play an important role in the coming fifth generation (5G) of mobile communications. For a smooth integration of satellite networks into the terrestrial ones, the standardization bodies are pushing for shared spectrum. Therefore, it is of interest to study satellite specific scenarios, the applicability of multicarrier waveforms that have already shown promise to meet the requirements of the future mobile networks. 5G candidate waveforms such as filtered orthogonal frequency division multiplexing (f-OFDM), filter bank multicarrier (FBMC), and universal filtered multi- carrier (UFMC) offer sharper out-of-band characteristics, significantly increasing the spectral efficiency. However, like OFDM, these waveforms exhibit a high peak to average power ratio (PAPR). A high PAPR saturates the nonlinear high power amplifier (HPA) which leads to nonlinear distortions in the on-board HPA's output. Moreover, signal clipping is often proposed in the literature to reduce the PAPR. However, clipping itself introduces nonlinear distortions within the signal bandwidth. Digital predistortion (DPD) can be applied to the clipped signal to remove the added nonlinear distortions while keeping the overall PAPR low. This chapter provides the simulation results on the application of the aforementioned waveforms to a satellite communication chain and presents the gains achieved by implementing DPD and clipping together in terms of PAPR, power spectral densities (PSDs), and bit error rates (BERs).