LDPC Coded Irregular Modulation Based on Degree Distribution

A novel irregular low density parity check (LDPC) coded link adaptation technique is presented to achieve flexible spectral efficiency and various reliabilities with irregular modulation. The mapping rule between LDPC coded bits and signal constellations is optimized in terms of LDPC code degree distribution and inherent unequal error protection property of irregular modulation. Simulation results show that the combination of various modulations can achieve not only fine data rate adaptation, but also better bit error rate (BER) performance with optimized mapping rule. Convergence performance is also analyzed using extrinsic information transfer (EXIT) chart based on actual probability dense function of extrinsic information by Monte Carlo simulations.