45 research outputs found
Design of Finite-Length Irregular Protograph Codes with Low Error Floors over the Binary-Input AWGN Channel Using Cyclic Liftings
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 satisfy a certain
approximate cycle extrinsic message degree (ACE) spectrum. The target ACE
spectrum is one with extremal properties, implying a good error floor
performance for the designed code. 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.Comment: Submitted to IEEE Trans. Communication
LDPCA code construction for Slepian-Wolf coding
Error correcting codes used for Distributed Source Coding (DSC) generally assume a random distribution of errors. However, in certain DSC applications, prediction of the error distribution is possible and thus this assumption fails, resulting in a sub-optimal performance. This letter considers the construction of rate-adaptive Low-Density Parity-Check (LDPC) codes where the edges of the variable nodes receiving unreliable information are distributed evenly among all the check nodes. Simulation results show that the proposed codes can reduce the gap to the theoretical bounds by up to 56% compared to traditional codes.peer-reviewe