Digital Video Services over Cable
When John Malone, CEO of TCI, talked about the 500 channel service in 1994, we surmise that he was referring to MPEG-2-encoded digital TV over HFC. HFC systems would be built with 750 MHz of forward bandwidth, offering 110 or more passbands of 6 MHz each. Each 6 MHz passband would be MPEG-2-encoded to yield four to six digital channels. Here's how.
Take 6 MHz and remove 500 kHz from each side for guard band, yielding 5 MHz. Use QAM 64 modulation on the 5 MHz. QAM-64 is selected by American and European standards bodies as the modulation scheme of choice for cable systems. QAM-64 encodes 6 bits per Hertz, yielding just over 30 Mb of raw throughput. Use Reed-Solomon forward error correction, which consumes ...
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