EXIT-Aided Bit Mapping Design for LDPC Coded Modulation with APSK Constellations

Abstract

In this paper, the bit mapping technique is applied to the low-density parity-check (LDPC) coded modulation system with Gray-APSK constellations for the first time. A multi-grid searching algorithm (MGSA) based on extrinsic information transfer (EXIT) chart analysis is first proposed to optimize the bit mapping distribution, after which a low-complexity bit mapper consisting of a structural bit interleaver and a demultiplexer (DEMUX) is devised. Compared to the LDPC coded QAM system specified in DVB-T2, the proposed APSK system with the optimized DEMUX can achieve up to 0.83dB gain under additive white Gaussian noise (AWGN) channel.