Efficient bit-interleaved APSK scheme for LDPC codes

This paper presents a new bit-interleaved higher-order APSK scheme for LDPC codes. Although the maximum decoding performance can be achieved using the maximum likelihood (ML) soft detection scheme, the complexity increases exponentially with the modulation orders. We approximate the ML soft detection scheme by applying the hard decision threshold (HDT) based method for a modified constellation of 32-APSK. In order to further improve the BER performance, we combined an efficient bit interleaving scheme, by considering that BER performance of each bit contained in a symbol is not uniform. Simulation results demonstrate that the proposed bit-interleaved scheme with very simple HDT based soft detection can achieve better performance compared to the ML detection of conventional scheme.