Soft decision estimation unit and maximum-likelihood sequence estimation unit

摘要

A metric calculating means calculates a first metric corresponding to a transmitted symbol sequence estimated by an adaptive equalizer, then calculates a second metric corresponding to a symbol sequence in which a symbol located at a position where a soft decision is made in the transmitted symbol sequence is inverted in polarity. Thereafter a subtracting portion subtracts the second metric from the first metric. Further, a multiplying portion multiplies the subtraction result from the subtracting portion by the symbol located at a position where the soft decision is made in the transmitted symbol sequence to generate a soft decision.