A Compact Construction for LDPC Codes using Permutation Polynomials

A construction is proposed for low density parity check codes using quadratic permutation polynomials over finite integer rings. Graph isomorphisms and automorphisms are identified and used in an efficient search for good codes. Graphs with girth as large as 12 were found. Upper bounds on the minimum Hamming distance are found algorithmically. The bounds indicate that the minimum distance grows with block length. One of the new codes has a similar error performance as the best known PEG LDPC code. Finally, the new codes are quasi-cyclic