PURPOSE:To obtain a viterbi decoding method adaptive for decoding by software by computing the other tables of seven groups with the table of one group out of eight groups at the output of a trellis encoder as reference. CONSTITUTION:Data Q6n-Q3n, Y2n, Y1n, and Y0n at the time (n) outputted from the trellis encoder are transmitted via a mapping part 2. Encode data inputted from a line is restored by a viterbi decoder. Thence, the data Q6n-Q3n, Y2n, Y1n, and Y0n are divided into eight groups segmented by Y2n, Y1n, and Y0n, and a transmission signal point is estimated from a reception signal point. At this time, the tables of other seven groups are computed by setting the table representing the signal point of one group as reference, and rotating and moving the signal point. Therefore, the decoding can be performed by the software without requiring the table classified by every group.
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