一种构造八环准循环LDLC码的搜索算法

A search algorithm to construct girth-8 quasi-cyclic LDLC

为了找到一种结构简单,又具有逼近香农限的线性码,应用构造准循环LDPC(low density parity check)码的算法思想,结合LDLC(low density lattice codes)的特点,对该算法进行改进,用以构造八环LDLC校验矩阵。保证LDLC生成序列在各行或各列中顺序和正负号的随机性以及在每行每列中元素分布的均匀性。同时分析了该算法的复杂度。在AWGN信道下仿真结果显示:用这种算法构造的八环LDLC的性能明显地好于现有的六环LDLC码的性能。

In order to find a kind of linear code with simple structure and approaching Shannon limit, based on the algo- rithm of constructing quasi-cyclic low density parity check （LDPC） codes and combined with the characteristic of low den- sity lattice codes （LDLC）, tbe LDLC witb girth-8 through improving the algorithm was constructed. The new algorithm en- sures the LDLC generating sequence distribute in each row or each column randomly and its uniformity in each row and each column. Meanwhile this article analyses the complexity of the algorithm. Simulation result in AWGN channel shows that the performance of girth-8 LDLC code using the proposed algorithm is better than the present girth-6 LDLC code.