METHOD AND SYSTEM FOR CALCULATING BRANCH METRIC USED BY SOFT DECISION DECODING ALGORITHM

摘要

PROBLEM TO BE SOLVED: To provide a calculation method for decreasing number of input bits while suppressing performance deterioration in a Viterbi decoder.;SOLUTION: In this invention, first a symbol (d) received from an antenna is demodulated to generate demodulation symbols (x) expressed in N bits. Then a maximum power (Pmax) is decided on the basis of the demodulation symbols (x). A scale factor (α) is obtained on the basis of a ratio of the maximum power to a soft decision maximum value (Bmax) expressed in M (M;N) bits. The scale factor is multiplied with the demodulation symbols, the value of demodulation symbols in excess of the soft decision maximum value is regarded as a soft decision maximum value and (N-M) bits among N bits of the demodulation symbols are rounded down to obtain an output symbol (y) in M bits. Then a branch metric(BM) is calculated on the basis of a distance between the output symbol and a predetermined symbol (C).;COPYRIGHT: (C)2002,JPO