Performance of a CE16QAM modem in a regenerative satellite system

Abstract

This paper studies a digital modem for use over a regenerative satellite link. Extensive computer-simulation tests have been carried out to determine the effects of bandlimiting, non-linear distortion and adjacent-channel interference on the tolerance to additive white Gaussian noise of the modem, using an equivalent baseband model of the transmission system. The results are used to select the preferred system arrangement. It has been shown that, with 4 dB output back-off (OBO) in the high power amplifier a bandwidth efficiency of 2.4 b/s Hz can be achieved, with an improvement in performance of 2.5 dB, relative to that of an ideal uncoded eight-phase-shift keyed (8PSK) signal, at a bit-error rate of 10-4.