SOFT DECISION APPARATUS AND SOFT DECISION METHO

PROBLEM TO BE SOLVED: To obtain a soft decision value as a value expressing a probability closer to an actual state, as much as possible through simple processing. SOLUTION: The soft decision apparatus outputs the soft decision value for each bit of each symbol to be used for decoding each symbol as a value, corresponding to a function value obtained by applying a predetermined function for each bit to a sample value of each symbol, on the basis of a demodulation signal in which a probability distribution of sample values at symbol points is a Gaussian distribution. In such a soft decision apparatus, each of the functions for each bit is approximated to a curve, representing the probability for each bit to be 1 or 0, with respect to the sample value of each symbol in the demodulation signal and is configured by using a quadratic function. COPYRIGHT: (C)2009,JPO&INPIT