Regular and irregular LDPC code design for bandwidth efficient BICM schemes

We consider low-density parity-check (LDPC) code design by considering the unequal error protection property in high order modulated bit-interleaved coded modulation (BICM) schemes. The existing work mainly considered the effect of variable node edge assignments on the decoding performance. In this paper, we consider both variable node and check node edge assignments to further optimize the LDPC codes for BICM schemes. To achieve this, we derive new extrinsic information transfer (EXIT) functions for both regular and irregular LDPC code ensembles. Then we employ differential evolution to optimize the code ensembles in terms of the lowest decoding threshold. Finally, we propose a modified progressive edge growth algorithm to design regular and irregular LDPC codes based on the optimized code ensembles. The numerical results show that our designed LDPC codes have better bit error rate performance compared to the codes designed in the existing work.