非规则LDPC码的局部消环

Local Loop Removal from Irregular LDPC Codes

低密度奇偶校验码(LDPC)中,度数低的节点之间的短环相比于度数高的节点之间的短环对于译码性能的影响更大。为了尽可能地减少短环,提出了一种交换节点之间的边的方法:首先最大可能地消去度数低的节点之间的短环,然后在保证度数低的节点之间最小环不变的情况下最大可能地消去整个LDPC码中的短环。对通过该方法与只从整体LDPC码上消去短环构造出LDPC码的仿真结果作出了比较。

In low-density parity-check（LDPC） codes,the small loops between low degree nodes are more detrimental to the decoding performance than those between high degree nodes.In order to reduce small loops,we propose a method of exchanging the edges between nodes.It first removes the small loops between low degree nodes as much as possible,and then removes the small loops from whole LDPC codes under the condition of ensuring the smallest loop between low degree nodes not to be changed.Finally,the simulation result of constructing LDPC codes by the method is compared with that by only removing the small loops from whole LDPC codes.