PEXIT Analysis and Design of Multilevel Coded Modulation With SPC-Aided SC-LDPC Codes

In this letter, we propose a multilevel coded modulation (MLCM) scheme based on single parity check (SPC)-aided spatially coupled low-density parity-check (SC-LDPC) codes to enhance spectral efficiency. A two-level MLCM framework is designed, in which the SC-LDPC component codes are compatible with the fifth-generation new radio (5G-NR) LDPC codes, and the message length allocations are optimized through the protograph-based extrinsic information transfer (PEXIT) analysis. Besides, an SPC constraint of message bits is introduced between different SC-LDPC codes to further lower the error floor. Simulation results demonstrate that the proposed MLCM scheme achieves significant gains over the conventional 5G-NR LDPC codes using bit-interleaved coded modulation, while also notably reducing decoding complexity.