Methods and systems for turbocoding and turbodecoding of quadruplet-pair type, comprising padding, two recursive convolutional codings in parallel, one with global interleaving

摘要

The method for turbocoding associates successive quadruplets of binary sequences (a,b,p,q) with information to be transmitted, where the information sequences (a,b) inclusive of padding bits are of a predetermined length k, and the parity sequences (p,q) are produced by use of interleaving (INT), that is a permutation, with switching (S) which exchanges the bits of information sequences (a,b). The parity sequences are generated by use of two retroaction polynomials (gh(x), g*(x)) with binary coefficients, of the same degree (delta), the period N, and the constant term equal to 1. The information sequences (a,b) and the interleaved sequences (c*,d*) contain 2(delta) padding bits, which are added to each series of 2(k-delta) information bits, where k is a predetermined multiple of the period N. The coding device (901) comprises a padding module (30) and a turbocoder block (40) containing two coders and a global interleaver (50) which carries out the permutation. The parity sequences (p, q) are determined by the polynomials p(x)=[a(x).f1(x)+b(x).f2(x)]/g(x), q(x)=[c*(x).f3(x)+d*(x). f4(x)]g*(x), where a(x), b(x), c*(x), d*(x), are the polynomials of degree (k-1), and f1(x), f2(x), f3(x), f4(x), are the polynomials with binary coefficients. The switching operation applied to the information sequences (a,b) consists of taking ci=bi, di=ai, for predetermined values of index i, and ci=ai, di=bi, for other values of i. The polynomials g(x) and g*(x) are identical. The interleaving (INT) includes a permutation pi(i) of the exponent for the index i in the range from 0 to (k-1), so that each integer pi(i) is congruent to (t+2r i) modulo N, where t and r are integers, or pi(i) is congruent to i modulo N, or pi(i) is residue modulo k of product (ie), where e is strictly positive integer, relatively prime to k and congruent to 1 modulo N. The method for turbodecoding allows the decoding of received sequences which were turbocoded before transmission. The decoding device comprises a turbodecoder block containing two global interleavers and an inverse global interleaver, and a depadding module for removing the padding bits. The apparatus for the transmission of coded digital signals comprises the coding device, and the apparatus for the reception of coded digital signals comprises the decoding device. The telecommunication network comprises the apparatus for the transmission and/or reception of coded digital signals. The permanent or portable data-storage means comprise the information program code instructions for the execution of method in steps. The computer program for controlling a programmable data-processing device implements the method.