INSERTION DELETION CORRECTION WITH SPECTRAL NULLS/

Levenshtein proposed a class of single insertion/deletion correcting c odes, based on the number-theoretic construction due to Varshamov and Tenengolt's. We present several interesting results on the binary stru cture of these codes, and their relation to constrained codes with nul ls in the power spectral density function. One surprising result is th at the higher order spectral null codes of Immink and Beenker are subc odes of balanced Levenshtein codes. Other spectral null subcodes with similar coding rates, may also be constructed. We furthermore present some coding schemes and spectral shaping markers which alleviate the f undamental restriction on Levenshtein's codes that the boundaries of e ach codeword should be known before insertion/deletion correction can be effected.