Coding for synchronous, fixed length decoding windows in the presence of insertion/deletion errors

It is firstly shown that the use of a fixed length decoding window in a channel that introduces insertions/deletions can propagate the errors to such an extent that stronger insertion/deletion correcting codes must be used. It is further shown that random insertion/deletion correcting codes based on the Levenshtein distance are not optimal for such channels. A modification to the Levenshtein distance is proposed and codes based on this distance are shown to be better suited to a channel with a fixed length decoding window. Rates of the codes based on the Levenshtein decoding distance are compared with that of codes based on the Levenshtein distance.