Design of length compatible quasi cyclic LDPC code

For some communication services, a class of channel coding corresponding to the variable code length is needed. Variable length LDPC codes construction algorithm is proposed for the need, which determines the shift factor in the parity check matrix according to short cycles and extrinsic information degree of the tanner graph, effectively avoiding the cycle of length 4 and cycle of length 6. Compared with 802.16e LDPC codes, rate of 1/2 codeword constructed by the algorithm has lower bit error rate and larger code length dynamic range, Which provides a valuable encoding scheme for communication service of variable information length.