To carry out error correction coding and decoding according to a serially concatenated
coded modulation system with a small circuit scale and high performance. A coding
apparatus 1 is designed so that an interleaver 20 interleaves order
of bits so that all weights are coded by a convolutional coder 30 with respect
to data comprising a series of 3 bits supplied from a convolutional coder 10;
the convolutional coder 30 makes as small as possible the total value of
the hamming distance of input bit between passes to be the minimum Euclidean distance
with respect to data of 3 bits supplied from the interleaver 20; and a multi-value
modulation mapping circuit 40 causes the hamming distance of input bits
in the convolutional coder 30 as the distance between signal point on the
I/Q plane is smaller to subject data of 3 bits supplied from the convolutional
coder 30 to mapping.
