We propose a technique to design finite-length irregular low-density parity-check (LDPC) codes over the binary-input additive white Gaussian noise (AWGN) channel with good performance in both the waterfall and the error floor region. The design process starts from a protograph which embodies a desirable degree distribution. This protograph is then lifted cyclically to a certain block length of interest. The lift is designed carefully to maximize the components of the approximate cycle extrinsic message degree (ACE) spectrum of the code's Tanner graph in a greedy fashion. As a consequence, the designed code would perform well in the error floor region. Moreover, the proposed construction results in quasi-cyclic codes which are attractive in practice due to simple encoder and decoder implementation. Simulation results are provided to demonstrate the effectiveness of the proposed construction in comparison with similar existing constructions.

ACE spectrum, approximate cycle extrinsic message degree (ACE), AWGN channel, cyclic lifting, error floor, finite-length LDPC codes, irregular LDPC codes, Low-density parity-check (LDPC) codes, protograph LDPC codes, quasi-cyclic LDPC codes
IEEE Transactions on Communications
Department of Systems and Computer Engineering

Asvadi, R. (Reza), Banihashemi, A, & Ahmadian-Attari, M. (Mahmoud). (2012). Design of finite-length irregular protograph codes with low error floors over the binary-input AWGN channel using cyclic liftings. IEEE Transactions on Communications, 60(4), 902–907. doi:10.1109/TCOMM.2012.030712.110086