ITERATIVE DECODING FOR PUNCTURED NO SYSTEMATIC CODES WITH BRIEF SOURCE ALPHABET AND RELATIVE SPEED 3b/4t AND 3b/4q

Abstract

Usually the scheme expected use of systematic convolutional component codes with a interleaver and a deinterleaver was applied to a research of properties of turbo-codes in the iterative decoder on the basis of a soft output Viterbi algorithm (SOVA). In works [4, 5] the version of the iterative decoder for using non-systematic component convolutional codes was developed and the recursive convolutional codes with the reduced entrance alphabet adapted for application as component codes of the coder of a turbo-code are synthesized. The technique of the description and determination of relative speed of codes with the reduced entrance alphabet coordinated with the standard method of calculation of relative speed of the perforated convolutional code is shown in the offered article. The matrix of perforation which was applied to riving of output characters of the synthesized turbo-codes is given. Results of modeling of transfer of a pseudorandom flow of binary data on the channel with the synthesized turbo-codes based on the modified Viterbi algorithm with a soft solution, with use of non-systematic recursive perforated component codes with the reduced entrance alphabet and relative speeds 3b/4t and 3b/4q are described. During of transfer on the channel distortion of data is carried out by an additive white Gaussian noise. Results of modeling are presented in the form of diagrams of characteristics of noise stability for not an encrypted channel and after one, two, three and five iterations of decoding by the developed decoder of turbo-codes. The analysis of the received results of modeling is made. Comparison of characteristics of noise stability of perforated versions of turbo-codes with nonperforated analogs by criterion of a power prize of coding is executed at the probability of an error of characters per=10-4.