Faster-than-Nyquist Signaling and Optimized Signal Constellation for High Spectral Efficiency Communications in Nonlinear Satellite Systems

We here consider utilizing faster-than-Nyquist (FTN) signaling to increase spectral efficiency in combination with using tight frequency roll-off, optimized signal constellations that have better energy efficiency, and allowing the satellite transponder to operate near its saturation. FTN provides a degree of freedom that allows for increasing the spectral efficiency without the need for introducing additional rings in the signal constellation, which is helpful in the presence of nonlinear transponders. Also, FTN allows for increasing the symbol rate without being adversely affected by the input multiplexing and output multiplexing (IMUX/OMUX) filters. This is because FTN does not alter the signal spectral shape. However, these advantages are gained at the expense of introducing distortion that needs to be compensated successfully. We then utilize an advanced Turbo Volterra receiver that compensates for FTN-induced distortion and nonlinear impairments. Through extensive simulations, we demonstrate substantial performance gains over a wide range of spectral efficiencies in nonlinear satellite systems with adjacent carriers.