J.83
A number of standards for the transmission of digital TV signals in broadband cable networks are listed in the ITU-T J.83 standard. The baseband signal in each case is the MPEG-2 transport stream. The standards do not depend on the video- and audio-coding method; usually, however, MPEG-2 video and MPEG-1 audio or Dolby digital audio are now used.
ITU-T J.83/A directly corresponds to the DVB-C methods developed in Europe for TV channels occupying a bandwidth of 8 MHz or 7 MHz. The modulation methods normally used are 64QAM or 256QAM, but other modulation schemes in between or below these two methods are also possible.
ITU-T J.83/B describes the broadband TV cable transmission method used in North America, where the channel bandwidth is 6 MHz. The main distinction is the completely different error protection (concatenated Reed-Solomon and Trellis coding) and the roll-off factor. The modulation methods correspond to those used in ITU-T J.83/A.
ITU-T J.83/C is basically nothing more than the adaptation of DVB-C to the 6 MHz world; error protection and modulation method are the same as in DVB-C, but the roll-off factor was changed. ITU-T J.83/C is used in Japan.
ITU-T J.83/D was derived from ATSC and utilizes 16VSB as modulation method. However, it is not used.
