Comparative performance analysis of M-CPSK and M-QAM over nonlinear satellite links

The classical moment technique is introduced as an accurate and efficient analytical tool for an end-to-end analysis of digital nonlinear satellite links. The method uses computational techniques that compute the symbol error probability when only the moments of the interference random variables are available. Using the moment method, analyses are presented for the symbol error probabilities of M-CPSK and M-QAM (quadrature amplitude modulation) through a band-limited nonlinear channel with both up-link and down-link noise and cochannel interference (CCI) preceding and following the transponder. The use of an onboard linearizer as well as a ground-based linearizer for M-QAM is also considered. It is shown that 16-QAM can be employed to increase the capacity of a typical C-band satellite communication link over a 4-GHz transponder up to 100 Mb/s with a ground-based linearizer and up to 140 Mb/s with a linearizer onboard the satellite. The results obtained using the moment technique are validated through the exhaustive method and brute-force computer simulation