Method for controlling a basic parity node of a non-binary ldpc code decoder, and corresponding basic parity node processor

A method for controlling an elementary parity node of a decoder for decoding non-binary LDPC codes or a code decoder using at least one non-binary parity constraint, said elementary parity node receiving first and second lists (U1,U2), referred to as first and second input lists, having nm elements sorted in an order defined among a descending order and an ascending order, nm being greater than 1, and delivering a list (Uout), referred to as the output list, having nm′ elements sorted in said defined order, nm′ being greater than 1, each element of the output list (Uout), being the result of a computing operation φ between an element of the first input list (U1) and an element of the second input list (U2), said computing operation φ being such that, if a≧b and c≧d, then φ(a, c)≧φ(b, d), said method including the following steps:

• a) selecting the p first elements of the first input list (U1) and the first element of the second input list (U2), p being a predetermined number less than nm,
• b) carrying out computing operations φ between the elements selected from the first input list (U1) and the element selected from the second input (U2) list so as to generate a list of p candidate elements for the output list,
• c) determining, from among the p candidate elements, the candidate element having the highest value if the defined order is the descending order, or the candidate element having the lowest value if the defined order is the ascending order, and inserting it into the output list (Uout), the candidate element inserted into the output list being the result of the computing operation φ between an element of order i of the first input list and an element of order j of the second input list, i and j being between 1 and nm,
• d) selecting, according to a predetermined criterion, the element of order i of the first input list and the element of order j+1 of the second input list or the element of order i+1 of the first input list and the element of order j of the second input list,
• e) carrying out a computing operation φ between the elements selected in the preceding step so as to generate a new candidate element, and replacing, in the list of p candidate elements, the last candidate element inserted into the output list by said new candidate element,
• f) determining, from among the p candidate elements, the candidate element having the highest value if the defined order is the descending order, or the candidate element having the lowest value if the defined order is the ascending order, and inserting it into the output list (Uout) in the order of determination, the candidate element inserted into the output list being the result of the computing operation between an element of order i of the first input list and an element of order j of the second input list, and
• g) repeating steps d) to f) until the output list comprises nm′ elements.