Design Of Short Frame Interleaver In Turbo Code

The emergence of Turbo code whose performances are close to Shannon limit is a milestone in the history of the development of coding theory. Turbo code has changed the people’s designing idea of the encoding method. The design method of channel coding has been changed from increasing the minimum hamming distance to reducing the number of low weight code word. Since1993, Turbo codes was proposed by C. Berrou etal, it has already become researching hotspot gradually in the coding information field because of excellent performance. Turbo code achieves random coding by using interleavers, and it takes on good performance. Therefore interleaver acts a very important part in turbo code system.The Research For Turbo codes and Interleaver includes the following aspects in this paper.(1) Describes the process of development and research status of Turbo Codes.(2) Analysed the encoder for coding theory, structure of encoder and the structure of the component encoder. Select the component codes investigate the effect on decoding performance. Also introduces principle of turbo decoding systemically and structure of decoder. Some decoding algorithm are compared, for instance, MAP algorithm based on maximum a posteriori probabilities, SOVA algorithm.(3)Describes the principles of the interleaver and several typical interleavers, and compared those typical interleavers. Analysed the effect of interleaver in Turbo code performance, concluded that we should do as much as possible to disrupt the relationship between the location of the original data in design a interleaver, to make short distance data far away as possible after interweave. In decoding, reduce the correlation in input information with a priori information as possible to make a good Turbo code performance.(4)Analysed the2,3and4input sequence effects on low code weight distribution, and apply the low code redistribution characteristics to minimum distance criterion. Exhaustive the2,3and4input sequence to select meet the standard set of candidate intertwined mapping. Combined with the IDS criterion, normalized the minimum distance threshold and IDS threshold as the final screening criteria.(5) Compared this interleaver and other interleavers in Matlab. This short frames interleaver compare frame error rate and bit error rate with the same as the length of the random interleaver and packet interleaver different SNR conditions, and corresponding summary.This interleaver design idea is a suboptimal method. Within a certain time complexity to find the ideal performance of the interleaved sequence, for different channel SNR we have normalized minimum hamming distance and IDS. Avoid unreasonable situation when consider only one criterion. Through simulation experiments, this design of short frame interleaver achieved the desired results, and the time complexity is acceptable. Moreover, This kind of interleaver can be actualized simply using hardware equipments and is valuable.