Data transmission device

A receiver for soft decision and decoding for deriving an appropriate soft-decision value so as to reduce the error rate at the output of a decoder such as a Viterbi decoder. A length V of continuous transmission sequences possible to be generated is set greater than a memory length L of a channel (V>L). By providing branch metric producing circuits as many as 2N (N=2V) and add/compare/select apparatus (ACS apparatus) of as many as N for respective states corresponding to combinations of transmission sequence data of V, the accuracy of a soft-decision value is enhanced. Further, a soft-decision value producing circuit performs a process not based on path metrics but based on survivor metrics. This allows a digital signal processor to easily perform the process.