Systematic codes for rank modulation

The goal of this paper is to construct systematic error-correcting codes for permutations and multi-permutations in the Kendall´s τ-metric. These codes are important in new applications such as rank modulation for flash memories. The construction is based on error-correcting codes for multi-permutations and a partition of the set of permutations into error-correcting codes. For a given large enough number of information symbols k, and for any integer t, we present a construction for (k + r, k) systematic t-error-correcting codes, for permutations from S_k+r, with less redundancy symbols than the number of redundancy symbols in the codes of the known constructions. In particular, for a given t and for sufficiently large k we can obtain r = t+1. The same construction is also applied to obtain related systematic error-correcting codes for multi-permutations.