low density parity check encoded signals propagated over a channel are decoded by iteratively producing messages representative of the a - posteriori probability of output decoded signals as a function of check - to - bit messages produced from bit - to - check messages via check - node update computation . the check - node update computation is performed as a min - sum approximation and the reliability of the output messages from the check - node update computation is determined by the least reliable incoming message m . the decoding includes : identifying the smallest and second smallest modulus of bit - to - check messages , the signs of output messages and the position of a least reliable incoming message , and producing an updated version of the messages representative of the a - posteriori probability as a function of the smallest or the second smallest of i - th check - to - bit messages , the signs of said output messages and the position of said least reliable incoming message .