对LZ77压缩数据的不均一纠错编码

提出一种对目前广泛使用的LZ77压缩数据进行高效误码保护的编码方法。分析了误码对LZ77压缩数据的影响，提出了对压缩数据的三个参数－匹配位置、匹配长度和未匹配字符进行不均一误码保护编码（Unequal Error Protection coding）。由于匹配长度中的误码对解压缩后的数据的危害比其余两个参数要很严重得多，且匹配长度中的误码出现得越早对解压缩后的数据的危害越大，而在其余两个参数中，误码的位置与解压缩后数据中的错误多少无关，所以，在整体上对匹配长度的保护强于对另外两个参数的保护，且对匹配长度的前面部份的纠错能力比对其后面部份更强一些；而对其余两个参数则用均一纠错编码保护。计算机模拟结果显示，所提出的编码方法在引入较少的监督位的情况下，比传统的纠错编码方法对解压缩后的数据的保护能力更强。

Unequal Error Correction for LZ77 Compressed Data

This paper proposed an efficient error control coding method for the data compressed by widely used LZ77 algorithm. Based on the analysis and computer simulation results of affections of errors in different components of compressed data, a Unequal Error Protection (UEP) coding method is recommended for the matched lengths, the offsets and unmatched characters of LZ77 compressed data. In general, matched lengths are better protected from errors than the other two because errors in matched lengths have much more serious affection to the decompressed data than the other two; and since the former the errors in matched length, the more serious the affections to decompressed data, while errors in other two have equal affections regardless their locations in compressed data, matched lengths are coded by using UEP codes, which can correct more errors in the former part. For the offsets and unmatched characters, an equal protection code is used. The principle of error control coding for LZ77 compressed data is that errors in matched length should be corrected as much as possible. Computer simulations show that the proposed method can control errors more efficiently in decompressed data than conventional error control codes although the redundancy introduced by proposed method is less than that of the conventional method.