Cable Technologists Explore Upstream Bandwidth Expansion
NEW ORLEANS -- Cable engineers are looking at various ways to boost their upstream bandwidth capacity for high-speed data, user-generated video, commercial services and other possible applications, they said at the Society of Cable Telecom Engineers (SCTE) convention. But don’t expect too many moves right away.
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Executives of Comcast, Time Warner Cable, Cox Communications, Cisco Systems and SCTE said they're looking at ways to increase their upstream spectrum as needed. Among other things, they're weighing whether to expand their overall capacity through plant upgrades, convert some downstream spectrum to upstream through mid-splits, top-splits, and module swaps or to use their upstream spectrum more efficiently with channel-bonding.
"A lot of bandwidth can be strung out of that” HFC network, said John Chapman, chief technology officer of Cisco’s access and transport technology group. Like the others, he expressed confidence that cable can meet any upstream bandwidth challenge.
Although they're exploring various upstream expansion options, cable operators don’t seem in a hurry to do anything now. Unlike the outlook on the downstream side, where operators are scrambling to carve out more bandwidth for HD programming and new video services, cable technologists don’t see a pressing demand for more upstream capacity over the next couple of years.
"For a while, we were pretty concerned about the upstream,” said Jay Rolls, senior vice president of technology for Cox Communications. “But then we realized the real problems were with the downstream. That’s really taken the pressure off the upstream.” He said cable may not have to create more upstream capacity for another five years.
Mike Hayashi, executive vice president of architecture, development, and engineering for Time Warner Cable, warned against upstream moves that could affect customer service. “I think it’s pretty challenging to touch anything in the plant,” he said. “We're a 24-hour business. … A module swap is not just a module swap."
But Daniel Howard, chief technology officer of SCTE, said cable operators may have to move more quickly than planned if the commercial-services sector continues to take off. He said operators may need more upstream bandwidth to deliver more symmetrical business services that rely on DOCSIS standards, such as metro Ethernet services.
Cable technology officials said they will continue to pursue different ways to carve out more spectrum in general, particularly for downstream services like HD. While Comcast, Time Warner, and Cox have taken different approaches, they intend to use some of the methods favored by the others as well.
For example, Time Warner Cable, which has relied heavily on switched digital video (SDV) technology to reuse digital spectrum, also plans to use plant upgrades, like Cox. And, like Comcast, Time Warner is considering the use of digital terminal adapters (DTAs) to reclaim analog bandwidth. “We opted to do switched video first,” Hayashi said. “For us to do both at once is too challenging. … But the truth is we're all going to be doing all of the above.”
Similarly, Comcast, which has been installing DTAs in subscribers’ homes, is starting to roll out SDV. DTAs didn’t offer “a technology solution,” said Steve Reynolds, senior vice president of consumer premises equipment and home networking at Comcast. “It was a business-driven solution. For us, reclamation made sense first. Now we'll do switched digital video.”
But the three largest cable operators will keep going their own ways on DOCSIS 3.0. While Comcast has almost finished launching D3 in all of its markets and Cox plans to roll out the wideband service in at least two-thirds of its regions by year-end, Time Warner Cable will continue to proceed slowly and cautiously. Plans call for Time Warner to offer D3 to no more than 20 percent of its subscribers by year-end.
"What matters is home demand and the competitive landscape,” Hayashi said. “We're deploying 3.0 in certain markets for competitive reasons. But we have other means to deliver more IP bits to the home."