Trellis coded modulation employing lower dimensionality convolutional encoder

摘要

Coding gain is improved by employing an N-dimensional trellis encoder incorporating an N'-dimensional convolutional encoder where N' is less than N. The additional coding gain is realized as a shaping gain. This unique modulator encodes a digital signal by generating a sequence of N-dimensional symbols as a function of the digital signal using an N'-dimensional convolutional encoder within the trellis encoder more than once (integer N/N' times) during each N-dimensional symbol interval. This allows the trellis encoder to produce an output of higher dimensionality than would normally be expected from the lower dimensionality convolutional encoder. The trellis encoder is applicable to television transmission.