Patent ID: 7120850

Claim:
A decoding method, implemented by executing a program embedded in a computer readable medium, of decoding a product code, in which symbols of each codeword are placed in a table comprising n 2 rows and n 1 columns, such that the symbols constituting each row form a permitted word of length n 1 according to a first component code to be decoded by means of an algorithm A 1 for correction with erasures, and the symbols constituting each column form a permitted word of length n 2 according to a second component code to be decoded by means of an algorithm A 2 for correction with erasures, said method being characterized in that it comprises a succession of main steps which are implemented until the correction of the received word is complete, each of these steps consisting in processing either a row or a column of said table in a predetermined order, and in that it comprises, to process a row i (1≦i≦n 2 ): a) applying the algorithm A 1 to the row i taking into account the τ 1 i erased positions (if any), b) if the algorithm A 1 is unable to correct the row, erasing all the symbols of that row, c) if the algorithm A 1 is able to correct the row, counting the number t 1 i of symbols whose value has been changed during the correction in the row to be corrected and of which it was not known in advance that they were to be corrected, and determining whether the result of this correction is reliable on the basis of the value of t 1 i and of the number τ 1 i of erased symbols in this row and, if the result is deemed reliable, accepting said correction, if the result is not deemed reliable, erasing all the symbols of that row, and in that it comprises, to process a column j (1≦j≦n 1 ): d) applying the algorithm A 2 to the column j taking into account the τ 2 j erased positions (if any), e) if the algorithm A 2 is unable to correct the column, erasing all the symbols of that column, f) if the algorithm A 2 is able to correct the column, counting the number t 2 j of symbols whose value has been changed during the correction in the column to be corrected and of which it was not known in advance that they were to be corrected, and determining whether the result of this correction is reliable on the basis of the value of t 2 j and of the number τ 2 j of erased symbols in this column and, if the result is deemed reliable, accepting said correction, if the result is not deemed reliable, erasing all the symbols of that column.