Gallager mapping based constellation shaping for LDPC-coded modulation systems

This paper focuses on the signal constellation shaping in LDPC coded modulation system. A novel constellation is presented by combining geometric shaping with probabilistic shaping based on quadrature amplitude modulation (QAM)constellation. With the shaped signal constellation, the signal mapping is optimized by using the extrinsic information transfer (EXIT) chart analysis. We further consider the nonbinary LDPC coded-modulation by combining with the proposed constellation shaping. Numerical results reveal that the proposed constellation can get the shaping gain without increasing the complexity of detection.