Research On The Minimum Distance Estimation Algorithms For Turbo Codes And Its Application In The Design Of Permutation Polynomial Interleavers

Turbo code schemes were immediately aroused a strong reaction of the communication sector since their excellent error correction performance which is near the Shannon limit and the channel coding theory has entered a new era. There are a lot of research achievements, but due to the given code parameters and rate, turbo code minimum distance is decided by interleaver performance so that the studies of turbo code minimum distance are not as block codes as quantitative analysis, therefore, the research that evaluation interleaver performance with turbo code minimum distance is not sufficient. Based on existing researches, this thesis focuses on the researches on the constrained sub-code and the all-zero iterative decoding for turbo code minimum distance and their application in the design of permutation polynomial interleaver.To begin with, the development of the channel coding and the background of turbo code scheme proposed are firstly presented, moreover, the practical significances of turbo code minimum distance and permutation polynomial interleaver are described, as well as organizations of this thesis. The basic principle of turbo codes is introduced, including the role of the interleaver and interleaver design criteria and the impact on interleaver performance generated by minimum distance.Subsequently, the algorithms of constrained sub-code and all-zero iterative decoding for estimating turbo code minimum distance are researched in the thesis. An analysis comparison of these two algorithms estimation of LTE3GPP188kinds of frame length turbo codes minimum distance with C language simulation is listed. The contrast analysis shows that the time complexity of the all-zero iterative decoding algorithm is much better than the constained sub-code algorithm and its estimated results are similar with constrained sub-code algorithm for medium or long interleaver length. Therefore, for the short frame turbo codes, the constrained sub-code algorithm should be selected to estimate minimum distance, for medium and long frame turbo codes, the all-zero iterative decoding algorithm should be considered.The existing literature shows that the decoding performances are poor for some quadratic permutation polynomial interleavers with best Ω’. They are optimized on a certain extent in this article and the optimized method is promoted and applied in the cubic permutation polynomial interleavers. The minimum distance of the quadratic and the cubic permutation polynomial interleavers with best Ω’ are estimated with the constrained sub-code algorithm and the results show that the minimum distances of optimized permutation polynomial interleavers with best Ω’ are slightly better than the ones of permutation polynomial interleaver with best Ω’ and their decoding performance simulations also prove this.