A time-saving algorithm for constructing QC-LDPC codes based on PEG algorithm

We propose a new algorithm based on PEG algorithm to construct high-girth quasi-cyclic low-density parity check (QC-LDPC) codes. Before our improved algorithm in introduction, we depict the general algorithm based on PEG algorithm to construct QC - LDPC code, if necessary to eliminate the short cycles, that would bring in cycles-search. When code length of basic matrix is not too long, the algorithm is feasible, but with the code length growth, cycles-search will bring large of calculation and time-consuming sharply. Therefore we put forward an improved method by using the specific relation of basic matrix rows to replace traditional cycles-search, effectively eliminates short cycles, and largely reduces the time complexity at the same time. Through the simulation analysis, the performance can also be comparable with random constructed LDPC codes.