Channeling the Channel
by Leslie Ellis // August 10 2009
Oftentimes, the language of technology mixes inextricably with the language of life. “Network” is a good example: there are the networks of television (ABC/CBS/NBC/Fox), and then there are the physical networks that carry TV networks, over air or wires, to homes.
This week’s translation is a back-to-basics look at another multi-dimensional, cross-disciplinary word: The channel.
To a consumer electronics manufacturer — and to Consumer Bob, sitting in front of the TV, remote in hand — a channel is a numbered destination for TV content.
To a programmer, a channel is them. The Discovery Channel. The Independent Film Channel. ESPN, A&E, Bravo, Lifetime, C-SPAN, all the way through the well, the channel lineup, they’re all channels.
That’s the mainstream usage, for the most part.
Even in tech-talk, “channel” has many hues. To an RF engineer, a “channel” can be the carriers that make up an analog TV signal, or it can be a defined, 6 MHz slice of radio frequency bandwidth.
To a digital video engineer, a channel might be a digitized, compressed stream of video, riding inside a 6 MHz channel.
To a broadband engineer, a channel is a DOCSIS carrier, capable of conveying 40 million bits of data, every second.
And to a tracker of cable bandwidth, a channel is a measure of capacity, 6 MHz wide, and capable of carrying two to three HDTV video streams, or 10 to 12 standard definition video streams, a ga-jillion voice-over-IP calls, or 40 Mbps of data.
And, let’s not forget this: Many (many) times when cable engineers say “QAM,” they mean “channel.” Because one QAM — quadrature amplitude modulator — is needed for every 6 MHz slot used to carry anything digital, the two terms, in tech lingo, are synonymous.
Here’s how this happens, conversationally. You’ll be talking with an engineer about VOD capacity. You ask how much room you’ll need, to keep up with anticipated consumer demand. The answer comes back like this: “We’re at four QAMs now for VOD, and over time maybe that goes to eight.”
QAMs, in that case, are the same as channels. They’re at four digital, 6 MHz channels now, allocated for VOD, going to eight over time.
This column originally appeared in the Platforms section of Multichannel News.