Patent ID: 6993703

Claim:
A decoder for decoding digital information from an encoded input signal received over a communication channel by determining a log likelihood logarithmically expressing a probability of passing a given state on the basis of a received value in the encoded input signal regarded as soft-input and decoding the digital information from said encoded input signal using the log likelihood said decoder comprising: an absolute value computation circuit for calculating a variable based on the absolute value of said received value; and a linear approximation means for calculating a correction term to be added to the log likelihood, the correction term being expressed in a one-dimensional function relative to said variable; said linear approximation means computing said correction term using a coefficient representing a gradient of said function for multiplying said variable, the coefficient being expressed as a power exponent of 2; wherein said linear approximation means discards bits from the lowest bit to the k-th lowest bit of the received value when the power exponent expressing the coefficient representing the gradient of said function is expressed by −2−k.