Improvements to APSK constellation with gray mapping
Amplitude phase shift keying (APSK) constellation with gray mapping proposed in [2] provides considerable shaping gain compared with quadrature amplitude modulation (QAM). In this paper, some improvements to APSK Constellation with gray mapping are addressed. AP-SK constellation with gray mapping could be adjusted according to different SNR levels to increase its average mutual information (AMI). Two methods to improve AMI, on phase and on amplitude, are proposed. Both AMI of coded modulation (CM-AMI) and AMI of bit-interleaved coded modulation (BICM-AMI) are considered. The improvements are verified by bit error rate simulations in both independent and iterative demapping scenarios.