Optimisation of 16APSK constellation with a new iterative decoder on the nonlinear channel

Amplitude phase shift keying (APSK) modulation presents an attractive scheme to overcome nonlinearity effects on nonlinear channels compared to conventional square quadrature amplitude modulation (QAM). In this paper, we investigate the performance of a bit interleaved coded modulation with iterative decoding (BICM-ID) system in which APSK modulation is used to achieve a spectral efficiency of 3 bit/s/Hz. A new iterative receiver is proposed where an extra soft-demapper is used between the two soft input soft output (SISOs) decoders. Extrinsic information exchange for the data and parity bits is optimised according to an appropriate iteration scheduling. Simulation results show a gain of 0.15 dB at a bit error rate (BER) of 10^-4 with this new iterative decoding scheme and the optimised constellation over a nonlinear satellite channel