Error performance analysis of a concatenated coding scheme with 64/256-QAM trellis coded modulation for the north American cable modem standard

Concatenated coding schemes with Reed-Solomon (RS) coding in the outer stage and trellis coded modulation (TCM) in the inner stage are analyzed. The TCM decoder incorporates a Viterbi decoder compliant with ITU-T Recommendation J.83, Annex B (north American digital video transmission specifications for multimedia cable network system (MCNS)). The module is suitable as the inner stage for a concatenated decoding scheme. A triple-error-correcting extended RS (128,122,7) code is used in the outer stage. Union bounds on the bit error performance of concatenated coding schemes, over 64- and 256-QAM signal constellations over AWGN channels are derived and verified by computer simulations. The effects of quantization of input symbols and of trace-back depth in the Viterbi decoder are simulated as well.