The algorith divides rows in to four equal groups. The rows are then used to from a distance graph which is then transformed into a matrix. girth of eight is maintained by avoiding six-cycles in the graph construction

Flexible construction of girth-six QC-LDPC Codes-The program constructs girth-six QC-LDPC codes given row-weight,k, column-weight,j, and sub-matrix size,m. The obtained parity-check matrix is stored in H. The construction has flexibility in that j,k

Design LDPC Codes without Cycles of Length 4 and 6