Comcast Eyes Gradual Move to DOCSIS 3.0

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Comcast hasn't let the cat out of the bag as to when — or where — it expects to launch “wideband” cable-modem service, with the promise of download speeds topping 100 Megabits per second.

But chief technology officer Tony Werner is confident that upgrading Comcast's networks to the Data Over Cable Service Interface Specification 3.0 will proceed as a natural evolution of the existing cable-modem infrastructure.

“The good news is that when we go to 3.0, we're backward-compatible with existing modems — so we don't have to rip out any modems,” Werner said.

And, in Werner's analysis, the headend side won't require a forklift upgrade either. Comcast typically has deployed chassis-based, integrated cable-modem termination systems from vendors that include Motorola and Arris Group.

Upgrading those systems to 3.0 will mostly be a matter of software, though some systems will require additional hardware blades, Werner said: “In my mind, this will be no harder than [migrating from] DOCSIS 1.0 to 1.1.”

Probably the hardest work, according to Werner, will be finding three additional 6-Megahertz channels to get the four necessary to achieve downstream connections of 160 Mbps. The DOCSIS 3.0 specification allows equipment to bond several channels together to act as a single virtual pipe. “We have a pretty good plan for channel recovery, but we have a lot of things that want that bandwidth.”

Werner said for Comcast there's “no business-case decision” today for deploying modular CMTSs — which split out functions into separate components — as opposed to integrated systems. A modular CMTS is supposed to give operators more flexibility by separating DOCSIS processing from edge quadrature amplitude modulation devices, allowing edge-QAM units to be deployed and allocated separately from the CMTS core.

Comcast for now plans to keep integrated CMTS architectures in place, adding 3.0 where it's needed. “We are buying CMTS blades and chassis on an ongoing basis,” Werner said, adding, “We're going to gradually evolve to a 3.0 footprint whether we like it or not.”

While DOCSIS 3.0 cable modems will be more expensive than 2.0 models, the additional cost will only be incurred “in the places you're selling a new service,” Werner said. Plus, the bill of materials costs are declining as DOCSIS 3.0 silicon vendors like Broadcom and Texas Instruments ramp up production.

With the next wave of CMTS hardware, the cost per port will come down, Werner said. A DOCSIS 3.0-compatible CMTS is “quite a bit less than half” the cost on a per-port basis of existing equipment.

Comcast is very close to initiating trials of DOCSIS 3.0 equipment. As for what services the operator will offer, Werner said, “We believe in having a very good high-speed premium service, but we're not necessarily saying we want to offer 100 or 160 Megabits” per second.

Factors Comcast will consider when deploying DOCSIS 3.0 include the competitive nature of a market, what new business services it could offer and whether there's an appetite for a premium Internet tier among consumers.

Pricing, too, will depend on what competing service providers — namely, Verizon Communications — sell in a given area. “The market is reasonably rational,” he said. “We're not going to be irrational.”

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