Intersymbol interference and precoding loss are minimized by combining the precodingand coding operations. An intersymbol interference coder uses a feedback loop to apply adither sequence to a sequence of input signal points. The dither signal applied to each inputsignal point is a function of the previous signal points in the sequence. The intersymbolinterference coder implements, for example, a trellis coding operation by selecting one ofseveral different modulo operations to determine the magnitude of the dither signal, theselection being made in response to the current trellis state. The sequence of signal pointsoutput from the intersymbol interference coder generates a valid sequence of the trellis codeinput to the Viterbi decoder.
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