A simple root-like bit mapping to improve the performance of LDPC-Coded QAM systems

This paper presents a new bit mapping strategy which aims to improve the performance of a LDPC-Coded QAM system such as the one specified in the G.hn standard. The proposed bit mapping is based on the assumption that bits transmitted in “good” sub-channels, with higher gains, help bits transmitted in “bad” sub-channels. This is possible by enforcing and prohibiting some connections between variable and check nodes in the Tanner graph, akin to Root-LDPC codes. The bit mapping is applied to G.hn, with QC-LDPC codes and QAM modulation. Simulation results show that the new bit mapping strategy improves performance for both single-carrier and OFDM-based systems.