A.Y. Barinov - Cherepovets Higher Military Engineering School of Radio Electronics E-mail: chvviur2@mil.ru

Reconstruction of turbo-like code (TC) in a priory uncertainty context is a challenging and half-solved problem. In this context, recon-struction problem consists of recovering the turbo-like structure, component codes and interleavers parameters from a noisy intercepted bitstream. The number of possibilities for component codes are quite small because low degree polynomials are usually used for TC and there are techniques that allow recovering component codes well. However the number of possibilities for component interleaver is extremely large and recovering its permutation vector in the presence of high noise is a difficult task. This article is about boosting accuracy of TC methods analysis via noise-immune method of TC interleavers identification. Method of TC interleavers identification is developed in conditions that structure and component codes of TC are known, TC is syste-matic, informational and coded bitstreams are known. Then, according to identification theory, new mathematical model of TC inter-leaved discrete sequence generation circuit is developed. This model is developed via polynomial and matrix analysis of the processes in this circuit. Mathematical model-s properties that significant for noiseless reconstruction of TC component interleavers and identification criteria are also developed. The Hamming weight of the sum (mod 2) of simulated and experimental stored data is chosen as the indicator of identification criterion. The developed method of TC interleavers identification is based on developed model properties and identification criteria. This method can be used for noise-immune identification of following TC cases: convolutional turbo code (TCC), TCC with puncturing of every second bit and repeat accumulate code, as flexible low density parity check code. For each case developed method has some peculiarities and realized via corresponding algorithms. Besides these cases method can be extend to some other TC kinds. Executed tests showed identification of all permutation vector for every TC in presence of bit error rate 10−2 and even higher. In conclusion the improved methods system of analysis of turbo-like codes discrete sequences is proposed. This methods system in-cludes known methods for reconstruction structure and component codes of TC and new developed method of TC interleavers identi-fication. Using improved methods system allows boost accuracy of turbo-like codes analysis up to 85%.

 

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