Double Serially Concatenated Convolutional Codes With Jointly Designed S-Type Permutors

The design of double serially concatenated convolutional codes with S-type permutors, i.e., permutors that provide a nontrivial separation, is considered. Based on a newly introduced parameter, namely, the so-called symbol span, a joint design of the outer and inner permutor is presented and its impact on the minimum distance of the overall code is analyzed. It is shown that a lower bound on the minimum distance that is given by the product of the free distances of all three component codes can be guaranteed. Design tables and simulation results are presented that include comparisons with single serially concatenated convolutional codes. In addition, a comparison with double/generalized repeat accumulate codes is briefly sketched.