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Cable Technology Feature Article

March 15, 2012

Eyeing Cable Bandwidth Upgrades

By Joan Engebretson, Contributing Editor

DOCSIS 3.0 has given cable operators a strong position in the residential broadband market, enabling them to offer services supporting speeds above 100 Mb/s. But the cable industry is already debating a range of approaches to increasing the bandwidth and/or capacity of cable systems. Also in the pipeline are ways to make bandwidth more symmetrical, as today’s residential broadband cable offerings provide considerably more bandwidth on the downstream path than they offer upstream.

I checked in recently with Daniel Howard, chief technology officer for the Society of Cable Telecommunications Engineers, to discuss the options.

Bandwidth boosting options

DOCSIS 3.0 is a broadband cable technology that works over hybrid fiber-coax networks to boost cable modem bandwidth by bonding multiple channels together. As Howard explained, about four downstream channels are bonded together in a typical DOCSIS 3.0 system—although systems with many more channels have also been demonstrated.

Like many forms of telecommunications, DOCSIS 3.0 relies on the idea that not all broadband subscribers in a neighborhood will be on line at the same time, meaning cable operators may eventually deploy fiber closer to the end user and re-architect the network so total bandwidth is shared between fewer homes. But Howard doesn’t see that as a high priority.

“Analog reclamation and a move toward unicast and going to 1 GHz transmission on the downstream are showing that [cable operators] can get [a lot of] mileage out of their existing plant,” said Howard.

Howard explained those three options in more detail.

Analog reclamation, he said, is when a cable company converts analog channels to more efficient digital transmission, thereby requiring less bandwidth per channel—an option Comcast (News - Alert) has used extensively. The cable operator can then bond more channels together to support broadband cable modem services.

A unicast approach transitions video content transmission from the cable industry’s traditional broadcast approach to more closely resemble the switched digital video approach that some telcos are using. With this approach, according to Howard, “you send the channel a customer is watching at that instant versus sending all channels simultaneously to everyone.”

Time Warner (News - Alert) is moving aggressively toward a unicast model,” Howard noted—and Charter, he said, is now almost exclusively digital video.

Upgrading to 1 GHz transmission from today’s typical 750-850 MHz transmission is an option chosen by Cox (News - Alert) Communications, Howard said. “They replaced the amplifiers that used to go to 750 or 850 MHz.”

A cable operator could potentially use various combinations of these three options to get an even bigger bandwidth boost.

The upstream path

There is another issue that cable operators will need to address as they strive to offer higher-bandwidth services to end users, however – and that’s the upstream path, which is considerably narrower than the upstream path on HFC systems and, some might say, is about maxed out.

Cable industry stakeholders are discussing dedicating more HFC bandwidth to upstream communications—and as Howard explained, several different approaches are currently being debated. Howard expects this to be a hot topic at upcoming cable industry events, including events sponsored by the NCTA (News - Alert) and the SCTE expo in October.

Edited by Braden Becker

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