On permutor designs based on cycles for serially concatenated convolutional codes

A new permutor design for serially concatenated convolutional codes is presented. It is based on the construction of a permutation matrix without short cycles of special types. For such a permutor, we give a lower bound on the minimum distance of the overall code that is significantly larger than that achievable with first-order separation (spreading factors). Additionally, the minimum distance can be attuned to the permutation length. This property may be useful for the construction of codes with moderate block lengths.