Girth 4 and Low Minimum Weights´ Problems of LDPC Codes in DVB-S2 and Solutions

Though LDPC codes have been accepted by DVB-S2, the LDPC encode of DVB-S2 (digital video broadcasting satellite second generation) are difficult to be implemented for their huge code lengths of 16200 bits and 64800 bits). To shorten the codes will lead the problems of girth-4 and lower weight codes. This paper analyzed the possible reasons leading to the problems, and revised the current code construction of DVB-S2. The simulation results in the AWGN channel show that the BER performance of the improved LDPC codes is much better than that of the former shorten codes.