Large-girth LDPC codes based on graphical models

In this paper we construct two classes of LDPC codes with girth 16 and 20, respectively, based on graphical models. These codes are well-structured, regular, and with column weight j = 2, which greatly simplifies their implementation. The codes with girth g = 16 have code rate r = 1/2. And the codes with girth g = 20 have code rate r = 1/3. Simulation results compare their bit-error-rate (BER) decoding performance in AWGN channels with randomly constructed LDPC codes.