Adaptive scaling of parity check messages for LDPC decoding

A method for decoding a codeword with a decoder of low-density parity check code (LDPC) code, said LDPC code being defined by a binary parity matrix of size M×N stored in a memory of the decoder, M and N being positive integers, the parity matrix corresponding to a representation of a bipartite graph comprising connections between M parity check nodes and N variable nodes, each line of the parity matrix corresponding to a parity equation associated with a parity check node, each column of the parity matrix corresponding to a variable associated with a variable node, each non-zero element of the parity matrix corresponding to a connection between a parity check node and a variable node, the codeword to be decoded corresponding to a set of values taken respectively by said variables, the method comprising executing one or more iterations by a processing unit until a stop criterion is met, each iteration comprising:

• calculating variable messages, for the different variable nodes, from parity check messages,
• calculating parity check messages, for the different parity check nodes, from the variable messages, wherein the parity check messages are stored in a first volatile memory of the decoder,
• when the calculated value of a parity check message or of an a posteriori estimation variable exceeds a predetermined saturation value, saturating said calculated value at said saturation value,
• calculating a posteriori estimation variables from the parity check messages, wherein the a posteriori estimation variables are stored in a second volatile memory of the decoder,
• wherein at the end of an iteration, when a saturation criterion is met, the processing unit performs a first scaling of the parity check messages and of the a posteriori estimation variables, a scaling corresponding to assigning to a value the integer with the same sign whose absolute value is the closest integer greater than the absolute value of the value divided by two, the saturation criterion being met when one or more of the following conditions is met:
• a number of saturations of the parity check messages is greater than or equal to a first saturation threshold,
• a number of saturations of the a posteriori estimation variables is greater than or equal to a second saturation threshold,
• a sum of the number of saturations of the parity check messages and of the number of saturations of the a posteriori estimation variables is greater than or equal to a third saturation threshold, and
• wherein, when the stop criterion is met, the method comprises outputting a decoded value of the codeword based on current values of the a posteriori estimation variables.