Joint Predistortion and PAPR Reduction in Multibeam Satellite Systems

Precoding for multibeam satellites with aggressive frequency reuse
has attracted interest of late towards enhancing system capacity.
Most of the works on precoding mitigate the linear co-channel
interference between the beams caused by frequency reuse. How-
ever, the high power amplifier (HPA), an integral part of the
satellite payload, is inherently non linear. Non-linear amplification
combined with the linear co-channel interference introduces non-
linear co-channel distortions at the receiver. Further, signals with
very high peak to average power ratios (PAPR), typical of spectrally
efficient modulations, are sensitive to the non-linear characteristic
of the HPA and necessitate large back-off to have manageable
distortion levels. In this work, a novel architecture comprising
multistream Crest Factor Reduction (signal pre-clipping) and Signal
Predistortion (SPD) in cascade, is devised to counter the non-
linearities and co-channel interference in multibeam satellite sys-
tems. An iterative algorithm to optimize the parameters of the signal
clipping and predistortion is devised taking recourse to analytical
derivations. The proposed joint estimation paradigm is shown to
compare favorably with state-of-art and provides a framework to
combine predistortion and precoding.