Power- and bandwidth-efficient communications using LDPC codes

We apply low-density parity-check (LDPC) codes to a bandwidth-efficient modulation scheme using multilevel coding, multistage decoding, and trellis-based signal shaping. Performance results based on density evolution and simulations are presented. Using irregular LDPC component codes of block length 10(5) and a 64-quadrature amplitude modulation signal constellation operating at 2 bits/dimension, a bit-error rate of 10(-5) is achieved at an E-b/N-O of 6.55 dB. At this value of E-b/N-O, the Shannon channel capacity, computed assuming equally likely signaling, is below 2 bits/dimension.