Patent FR-2829636-A1 (FR)
Title: Method for qualifying the error-correcting codes, optimization method, coder, decoder, and the corresponding application
Inventor: BERROU CLAUDE
IPC: H03M13/29
Filed: 2001-09-11
Abstract: The qualification method delivering the code words each formed of at least one symbol associates with the code an information of qualification representative of the capacity of a corresponding decoder to correct the errors, which is obtained by an estimation process comprised in the determination of a pulse distance (d) in block (24), and includes two substeps: (i) the insertion of a predetermined error pulse which introduces a perturbation on a set of at least one symbol of a reference code word preliminary coded without error, and (ii) the decoding of the code word modified by the error pulse by use of a weighted-inputs decoder and analysis of the decoding result which delivers the information of qualification.  The set contains one symbol, or at least two symbols belonging to a code word concurrent with the reference code word. The qualification method associates the set of at least one symbol affected by the error pulse with an intermediary datum of qualification, where the function of maximum amplitude of the error pulse does not perturb the decoding of the code word. The estimation process is repeated by incrementing the index in block (26) at least two times thus introducing a perturbation on the same set with variable amplitudes of the error pulse so to determine the pulse distance. The estimation process is repeated in a test block (28) for at least two distinct sets of symbols of the reference code word. The information of qualification is the minimum pulse distance (d) found among the determined pulse distances. The multiplicity (m) representative of the number of sets more sensitive to the error pulse is determined in block (27) as the second information of qualification, in addition to the minimum pulse distance. The sets are selected to take into account eventual periodicity of the code. The reference code word is a word whose all symbols take binary 0 value. The reference code word is subjected to a modulation in block (22) before the error pulse is inserted. The qualification method comprises a step of estimating asymptotic gain representative of the efficiency of the error-correcting code with respect to the absence of coding. The reference code word is generated and modulated in block (22), and at least one set of at least one symbol of the reference code word is selected by blocks (23,26) by setting and incrementing the index (i). The amplitude of the error pulse is varied according to a determined rule. The code belongs to a group comprising convolutional codes, convolutional turbo-codes, algebraic turbo-codes, parallel concatenated codes, serial concatenated codes, convolutional turbo-codes, algebraic method for optimizing a channel coding implements the method for qualifying an error-correcting code on at least two candidate codes and a step for selecting of the candidate codes by analyzing the information of qualification. The coder allows the correction of errors, and the decoder allows the decoding of data coded by an error-correcting code and a corresponding error correction. The application of the qualification method belongs to a group comprising the transmission of data in a noisy channel, the optimization of the coding channel with unequal protection, the estimation of the free distance of a code, and the estimation of code performance.