An Improved Design of Gallager Mapping for LDPC-coded BICM-ID System

Abstract

Gallager mapping uses different signal points with different probabilities by assigning several labels for one signal point, and thus provides a promising approach to achieving shaping gains. An important issue in Gallager mapping is how to assign labels for signal points. In this paper, two optimized design rules for Gallager mapping of bit-interleaved coded modulation scheme with iterative decoding (BICM-ID) are proposed, where the Hamming distance among the labels for one signal point should be minimized. The extrinsic information transfer (EXIT) technique is utilized to design and analyze the proposed mapping patterns. Compared with conventional Gallager mapping, our proposed method provides extra shaping gain for the LDPC-coded BICM-ID system. And our proposed method supplies better performance than conventional uniform mapping with the same spectrum efficiency.