LT码编译码分析及改进

Analysis and improvement for coding-decoding of LT code

数字喷泉码是一类不受限的纠错码,即从原始数据分组编码产生的编码分组序列是无限的。通过研究数字喷泉码中译码终止的原因,得出在数字喷泉码中,译码终止是由于缺少度数为1的编码包,导致译码提前终止以至译码失败。注意到度数为2的编码包在整个编码包中占有很高的比例;因此,将数据包分成两组,在度数为2时,分别从两组中取出数据,这样可以有效地提高数据的覆盖率,降低译码提前终止的概率。通过对编码算法的改进,提高整个数字喷泉码的译码成功率。

Digital fountain code is a class of rateless erasure code. The number of encoded symbols that is generated from the original data is potentially limitless. By the relative study,the reason of decoding termination of digital fountain code was found,which caused by the lack of degree-1 encode packages,and may lead to decode terminate ahead of time and decoding failure. Because of this,it is found that the degree-2 encode packages occupies a high proportion in the whole encode packages. Therefore,the data package is divided into two groups. When the degree is 2,the data is taken out respectively from the two groups. In this way,the coverage of data can be improved effectively,and the probability of decoding termination in advance can be reduced. With the improvement of coding algorithm,the decoding success rate of digital fountain code was improved.