Cable Flips the Switch
Switched broadcast frees up valuable bandwidth
By Glen Dickson -- Broadcasting & Cable, 4/23/2006 8:00:00 PM
As cable operators look to offer new and better services to stave off competition from satellite operators and telcos, they are borrowing some elements from the competition. That includes the “switched-broadcast” techniques that AT&T plans to use to provide video over its advanced DSL network this year.
In the traditional distribution model, cable operators deliver hundreds of channels to a subscriber's home, though the subscriber can view only one at a time. The concept of switched broadcast is that, instead of simultaneously delivering hundreds of channels to a home, cable operators deliver only one channel to a digital set-top box at a time, freeing up bandwidth for faster data services and more telephony traffic.
The efficiencies gained across cable's hybrid fiber-coax (HFC) network by using switched broadcast will also allow operators to add new programming, including more HD networks.
Scientific-Atlanta and BigBand Net­works both demonstrated switched-broadcast products at NCTA's recent National Show, and major cable operators detailed their switched-broadcast plans in a panel session.
Time Warner Cable is already rolling it out in Austin, Texas, and Columbia, S.C., and will likely deploy it in four to six systems this year. Chief Technology Officer Mike LaJoie thinks it's the answer to bandwidth challenges. “I don't think it's 10 years away; it's much closer than that,” he says. “The whole notion of channelized video will go away.”
Cox Communications has been “toying with switched broadcast” for several years, says Chief Technology Officer Chris Bowick, and will probably deploy the technology in two markets this year. In the near term, Cox is focused on reclaiming bandwidth by deploying “digital simulcast”—converting the analog tier to digital for delivery to digital cable customers.
Comcast CTO David Fellows says “switching offers infinite choice.” Comcast has not deployed the technology yet, instead focusing on rolling out digital simulcast. By using technologies like switched broadcast and digital simulcast, he says, cable networks can compete against the fiber-to-the-home architecture used by phone company Verizon. “In the long run, we'll be okay,” says Fellows. “Right now, we have two-thirds of our bandwidth tied up with analog video.”
Scientific-Atlanta, a Cisco subsidiary, is providing its switched-broadcast technology to both cable operators and AT&T. Jeff Taylor, director of product strategy for Scientific-Atlanta, says its IP-based switched-broadcast system is slightly different from video-on-demand technology.
With VOD, operators set up a one-to-one “session” with a digital set-top to deliver programming. With switched broadcast, operators still transmit hundreds of channels, or “multi­cast,” down to fiber hubs that might serve 500-2,000 homes, where they will run through an “edge router.” When a subscriber served by that hub changes channels, the edge router sends the selected stream to the home over coax, and the set-top will “join” the multicast session.
The key to switched broadcast, says Taylor, is that customers don't know what's happening in the background because there's no noticeable delay in changing channels. “They want a transparent consumer experience,” he says.
To that end, Scientific-Atlanta demonstrated a traditional digital cable feed next to a switched-broadcast one. The channel change for switched broadcast took about as long as the one for a standard feed, a little over two seconds.
Insight Communications doesn't have a schedule to deploy switched broadcast yet but does plan to reclaim analog spectrum via digital simulcast. President/CEO Michael Willner nonetheless finds the concept of switched broadcast intriguing. Says Willner, “It was one of the more interesting things at the show.”
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