Abstract:In order to improve the channel time-varying and the transmission reliability of satellite laser communications, a novel construction method of protograph quasi-cyclic low-density parity-check (QC-LDPC) codes based on the Zig-Zag (ZZ) structure is proposed. This construction method combines the protograph with the method of designing the shift coefficient of the Zig-Zag structure to construct the ZZ-QC-LDPC code with the check matrix of the girth-8 and the flexibly adjustable code-length code-rate. The simulation results show that under the same code-rate, the net coding gains of the ZZ-QC-LDPC code constructed by the proposed construction method, compared with the QC-LDPC code based on the arithmetic progression and protograph and the QC-LDPC code based on the greatest common divisor as well as the QC-LDPC code based on the large-girth fast encoding characteristics, can be improved by about 0.2,0.1 and 0.64dB respectively at the bit error ratio of 10-6, furthermore, the ZZ-QC-LDPC code has the more excellent error-correcting performance within the wider code-rate range.