Importance

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Abstract

An outer symbol error correcting code is concatenated with a punctured multidimensional trellis code to provide an optimal scheme for communicating digital television signals in a standard (e.g., approximately six MHz) bandwidth channel via a cable television network or the like. An input signal is encoded using an outer symbol error correcting code to produce successive blocks. Each block comprises N seven-bit coded symbols of which M represent information to be communicated and the remaining N-M coded symbols comprise error correcting information. M/N is either 120/126, 121/127 or 122/128. The blocks are interleaved, and may be supplemented with control symbols that include a synchronization pattern for M/N=121/127 or M/N=122/128. The interleaved blocks are convolutionally encoded using an inner trellis code having a punctured rate 4/5 (sixty-four QAM) or 3/4 (sixteen QAM). The output symbols are multilevel modulated for transmission over a communication path using, for example, sixteen or sixty-four QAM. The transmitted symbols are decoded using a trellis decoder, deinterleaved, and further decoded in an outer symbol error decoder concatenated with the inner trellis decoder.

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First Claim