The Design of Quasi-cyclic LDPC Codes Based on Cyclic Difference Sets

Combining the perfect cyclic difference sets with the quasi-cyclic codes,a new algorithm for constructing QC-LDPC codes based on cyclic difference sets is proposed.First,the author obtains a small initial matrix that meet the requirements of the weights based on cyclic difference sets,and then the zeros elements,non-zero elements of the initial matrix are replaced by all-zero matrices and cyclic shift matrices.For the purpose of determining the shift coefficient,the cycle length of six is eliminated by computer searching.Simulations show that,under the AWGN channel and the BP decoding algorithm,our QC-LDPC codes are better than the random LDPC codes in the bit error rate and they are more proper for hardware implementation.