Multilevel coding for low-density parity-check codes

In recent years attention has turned to LDPC codes, which show performance approaching communication path capacity. In the past, application of LDPC codes has mainly been BPSK-based proposals. In this paper, we propose a new design method for multilevel coding that uses LDPC codes as element codes. First, we focus on the possibility of freedom of design for LDPC codes in regards to any desired encoding rate, optimize a degree profile using Gaussian Approximation, and use the actual BER characteristics shown in LDPC codes of finite length formed by this degree file to find the differential SNR_norm up to the Shannon limit of SNR values at the time of some specific BER. With the SNR_norm for the encoding rate at several points, we calculate an SNR_norm approximation formula for a continuous, wide-range encoding rate, and use this approximation formula to propose a method for designing multivalue coded modulation based on multilevel coding. In addition, we demonstrate the results of a simulation of this proposed method using irregular EG-LDPC codes, and demonstrate that this method is effective for restricting deterioration of performance in actual usage. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(8): 57–68, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20173 Copyright © 2004 Wiley Periodicals, Inc.Copyright © 2007 Wiley Periodicals, Inc.