Distance spectrum of the turbo-codes

An analytical approach to newly invented turbo codes (TC) is presented. That approach is based on evaluating the properties of TC by means of the minimum Hamming distance (MHD) and the Hamming distance spectrum (HDS). An algorithm for computing HDS is presented and numerical results are discussed. The concept of basic return-to-zero sequence is introduced. It is shown how basic return-to-zero sequences can be used in the algorithm for computing HDS and how it can justify the properties of TC. Numerical results of computing MHD and HDS for different TCs are presented and verified by simulations.