PERFORMANCE OF TRELLIS CODED 16-QAM IN A TWO-LINK SATELLITE CHANNEL

摘要

This paper studies the performance of a Trellis-coded 16-ary QAM signalling transmitted through a two-link,nonlinear satellite channel.A 3/4-rate coding and a 4-state,simple convolutional encoder is considered.The bandlimited signal is distorted by nonlinear amplifier on board satellite which introduces AM-AM and AM-PM conversions.Additive White Gaussian Noise (AWGN)is assumed to be added to the signal on both up and down links.Bit error rates (BERs) are computed for uncoded 8-ary CPSK and Trellis coded 16-ary QAM transmissions as a function of up and down link carrier-to-noise ratios (CNRs).A raised cosine filter with a roll-off factor of α=0.4 equally split between the transmitter and receiver giving a spectral efficiency of 2.14 b/s/Hz is assumed.It is shown that as OBO is increased coding gain is also increased and can reach a value of over 3dB.However,when the best performances of the two signallings are compared the coding gain is about 1 dB.