A fast algorithm to estimate the distance spectrum of turbo codes and tail-biting turbo codes

The computational complexity required by the complete calculation of the distance spectrum of turbo codes, even limited to low weight input sequences, makes it too slow for practical purposes such as interleaver optimization or effective bit error rate bounding. In this paper, a fast algorithm for distance spectrum estimation purposes is presented. A comparison with complete computed spectra, theoretically derived spectra and results from previous works will be presented for both deterministic and uniform interleaver