Multilevel coded 16-QAM modulation with multistage decoding and unequal error protection

A new construction for multilevel coded modulation with multistage decoding and unequal error protection is proposed and analyzed for both symmetric and asymmetric 16-QAM constellations. It is shown that the conventional upper bound originally derived for PSK signaling is loose when applied to QAM. A new tight approximated upper bound is proposed for 16-QAM and the partitioning considered. The proposed multilevel codes provide a larger proportion of most important bits (MIB) than in previous constructions.