Optimal Systematic t-Deletion Correcting Codes

Abstract

Systematic deletion correcting codes play an important role in applications of document exchange. Yet despite a series of recent advances made in deletion correcting codes, most of them are non-systematic. To the best of the authors' knowledge, the only known deterministic systematic t-deletion correcting code constructions with rate approaching 1 achieve O(t log <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> n) bits of redundancy for constant t, where n is the code length. In this paper, we propose a systematic t-deletion correcting code construction that achieves 4t log n + o(log n) bits of redundancy, which is asymptotically within a factor of 4 from being optimal. Our encoding and decoding algorithms have complexity O(n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2t+1</sup> ), which is polynomial for constant t.