March 1, 2010

Comcast: Headends Getting Too Crowded

CMAP is all about saving space, according to Jorge Salinger, VP access architecture, office of the CTO, Comcast, at an event in Denver last week.

Of course, saving space occupied by expensive telecommunications equipment translates into saving money, too.

Converged multiservice access platform (CMAP), part of a Next Generation Access Architecture (NGAA) that Comcast unveiled a year ago, was the first topic of discussion at Light Reading's conference "Cable Next-Gen Broadband Strategies."

Salinger wrote a detailed description of CMAP for the February issue of Communications Technology. (For more, click here).

At the Light Reading event, Salinger said Comcast recognizes that its headends and hubs are going to be stressed in the near future to support additional QAMs. A lot of the pressure is coming from the demand for more narrowcast services such as video on demand (VOD).

"We see we can probably double the number of CMTSs, but we couldn't possibly triple them," he said. "Same thing with VOD QAMs: We couldn't triple or quadruple them, but we need to do that."

Besides the fact that it's extremely expensive to enlarge headends and hubs and expensive to power them, in some cases it's not even possible, where headends are built in crowded urban areas with no room to expand.

So Comcast is pursuing this CMAP option, which boils down to the MSO specifying an entirely new set of equipment.

The goal is to develop a new box that combines all QAMs into one RF port, with the capability to provide all services, including high-speed data, voice, video, VOD and switched digital video (SDV). In addition, the box would handle video encryption and PON for business services.

Working with vendors

Comcast is working with lots of vendors and keeping other MSOs and CableLabs in the loop as it develops this box.

"Everybody you can think of is involved in this process," said Salinger.

Ultimately, Comcast wants to be able to service 40 service groups out of 16 rack units, with a density of about 2 ½ service groups per RU, he said.

In addition to the huge space savings, another big benefit will be the flexibility and simplification of assigning QAMs for different service groups. The operator won't have to align services for different applications into a common subset of homes for each service group.

Also noteworthy is that Comcast is approaching DOCSIS differently for CMAP.

"We think of DOCSIS as software in this box, rather than hardware," he said. "It's a paradigm shift."

Salinger said the space savings from CMAP will be "enormous" and "jaw dropping," estimating that the MSO will be able to double its number of service groups.

In a later session at last week's conference, Chris Bastian, senior director of network architecture, Comcast Cable, talked about DOCSIS 3.0 and the wideband horizon.

He said before CMAP, the MSO is still working to increase densities on existing chassis.

"We want to get the value out of them for the next two to five years," said Bastian. "On roadmaps, CMTSs have denser blades."

-Linda Hardesty