Tuesday, July 3, 2007

Comcast says it Could; Not "Would"

“We’re not necessarily saying we want to offer 100 or 160 megabits” per second access speeds, says Comcast CTO Tony Werner, referring to the DOCSIS 3.0 upgrade Comcast is planning. Using channel bonding, DOCSIS allows a cable operator to support downstram bandwidth as high as 480 Mbps and upstream as high as 120 Mbps, on a shared basis.

And that’s the key. Two bonded TV channels (6 MHz each) will support that amount of bandwidth from a fiber node to customers served off that node, possibly an area of 500 or more homes in any given location. At 60 percent video penetration and 30 percent cable modem penetration, that implies a potential customer base of about 90 homes or businesses.

If three customers really wanted 150 Mbps downstream and 40 Mbps upstream, that would chew up 12 MHz of bandwidth, equivalent to two analog TV channels.

So unless a cable operator wants to reclaim a fairly significant amount of television bandwidth, it isn’t going to be able to provide such speeds to more than one or two customers in a fiber-served area.

The DOCSIS 3.0 upgrade is supposed to start in 2008.

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