Abstract:

Since the generator matrices of the LDPC code are always non-sparse, it is hard to store a large generator matrix when the code-length is long. Moreover, time complexity of encoding with a generator matrix is high. In order to resolve this problem, we present a new design of quasi-cyclic (QC) LDPC code for fast encoding. Unlike other QC codes, the parity check matrices of the proposed QC codes not only have the quasi-cycle characteristic, but also contain sub-matrices with the quasi-diagonal structures. So the parity check matrices have approximate lower triangular structures. According to Richardson’s fast encoding algorithm, the parity check matrices with these structures can realize fast encoding by the parity check matrices. Therefore we can avoid the difficulties of storage difficulty and time complexity. Simulation in AWGN channels shows that the BER performance of the proposed codes is excellent in different code-lengths and code-rates.

Key words: communication, quasi-cyclic low-density parity-check codes, fast encoding, BER performance