Method and apparatus for communicating multilevel modulated data using concatenated coding.

摘要

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 (10) is encoded using an outer symbol error correcting code (12) 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 (18), and may be supplemented with control symbols (19) 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 (20) having a punctured rate 4/5 (sixty-four QAM) or 3/4 (sixteen QAM). The output symbols are multilevel modulated (21) for transmission over a communication path (26) using, for example, sixteen or sixty-four QAM. The transmitted symbols are decoded using a trellis decoder (32), deinterleaved (34), and further decoded in an outer symbol error decoder (36) concatenated with the inner trellis decoder (32).