Improving DVB-S2 Performance Through Constellation Shaping and Iterative Demapping

Because it is widely supported by Commercial-Off-The-Shelf (COTS) technology, the DVB-S2 waveform standard has become an attractive solution for military communication links. The waveform uses a combination of Amplitude-Phase-Shift Keying (APSK) modulation and Low-Density Parity-Check (LDPC) codes. Typical DVB-S2 implementations select signals from the APSK signal set with uniform probability. However, information-theoretic results suggest that performance may be improved by selecting lower-energy signals more frequently than higher-energy signals. In this paper, the authors propose and analyze a DVB-S2-compatible system that shapes the APSK constellation by selecting signals with a non-uniform probability. The receiver iterates between the APSK de-mapper, the shaping decoder, and the LDPC decoder.