Low Density Parity Check codes with quasi-cyclic structure and zigzag pattern

Low-Density Parity-Check (LDPC) codes with linear time encoding complexity and low hardware storage are a hot issue recently. We propose a general method for constructing LDPC codes with quasi-cyclic (QC) structure and improved zigzag pattern to obtain both linear time encoding and low hardware storage. We call it irregular repeat accumulate like (IRA-like) codes for its similarity with irregular repeat accumulate (IRA) codes. Through the optimization-constraint of QC-LDPC codes and the modification of dual diagonal structure we have acquired IRA-like codes with reduced number of low-weight codewords and short cycles. Extensive simulation results show that the IRA-like codes not only achieve better performance than some kinds of classical LDPC codes but also have much better practicability. Compared with the LDPC code applied in China Mobile Multimedia Broadcasting (CMMB), IRA-like code significantly outperforms the CMMB-LDPC code about 0.18 dB at BER=10^-5.