Improvements to Burrows-Wheeler compression algorithm

In 1994 Burrows and Wheeler presented a new algorithm for lossless data compression. The compression ratio that can be achieved using their algorithm is comparable with the best known other algorithms, whilst its complexity is relatively small. In this paper we explain the internals of this algorithm and discuss its various modifications that have been presented so far. Then we propose new improvements for its effectiveness. They allow us to obtain a compression ratio equal to 2.271 bpc for the Calgary Corpus files, which is the best result in the class of Burrows-Wheeler transform based algorithms.