. . . . "eing an integer, m is an even integer no smaller than 4, and the constellation has 1.5??2r+1 signals; the encoder is further arranged (e.g., by means of a single-parity-check code, a Hamming code, or a state-transition trellis) so that one signal point for each block may be drawn from among all signals in the constellation, m-2 of the signal points are drawn from groups that depend on the group fr" .