Construction of codes protographes LDPC quasi-cycliques based on an arithmetic progression

In this document, we study the construction of codes LDPC quasi cyclic based on a protograph. In addition to their large perimeters, the presented codes take profit from the advantages of bass coding and decoding complexity. The aim of this article is to make an improvement on the implementation of quasi-cyclic LDPC codes. Thus to respect the structure of the basic protograph we use an arithmetic progression to determine in advance the positions of certain nodes of control in the derived graph, which turn to some extent amounts generating a new model while proceeding to an enlarging of the basic protograph. Once this new model conceived we apply the usual techniques to build in an optimal way the derived graph.