Switched Broadcast a Hot Topic at NCTA


As cable operators look to offer new services and more HD programming to stave off competition from satellite operators and telcos, they are experimenting with some of the same "switched broadcast" techniques that telco AT&T plans to use to provide video over its advanced DSL network later this year.

In the traditional distribution model, cable operators deliver hundreds of channels to a subscriber's home, though the subscriber can only view one channel at a time on a given television set. The concept of switched broadcast is that, instead of simultaneously delivering hundreds of channels to a subscriber’s home, cable operators will only deliver one channel to a digital set-top box at a time, thus freeing up bandwidth for faster data services and more telephony traffic. The overall 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.

Technology vendors Scientific-Atlanta and BigBand Networks were both demonstrating switched broadcast products at the NCTA show in Atlanta this week, and technology chiefs from major operators detailed their switched-broadcast plans in a Monday panel session.

Time Warner Cable is already rolling out switched broadcast in Austin, Texas, and Columbia, S.C., says chief technology officer Mike LaJoie, and will probably deploy it in four to six systems this year. He thinks switching is the answer to cable’s bandwidth challenges, and says that "I don’t think it’s 10 years away, it’s much closer than that. The whole notion of channelized video will go away."

Cox Communications has been "toying with switched broadcast" for several years, says Cox Communications Chief Technology Officer Chris Bowick, and will probably deploy the technology in two markets this year. He says in the near term, Cox is more focused on reclaiming bandwidth by deploying "digital simulcast," taking the current analog tier and converting it to digital for delivery to digital cable customers.

Comcast CTO David Fellows says that "switching offers infinite choice." Comcast has not deployed the technology yet but instead has focused on rolling out digital simulcast. He says that, by using technologies like switched broadcast and digital simulcast, cable’s network will be adequate to compete against the fiber-to-the-home architecture being 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 (VOD) technology. With VOD, operators set up a one-to-one "session" with a digital set-top to deliver programming. With switched broadcast, operators will still transmit hundreds of channels, or "multicast," down to fiber hubs that might serve 500 to 2,000 homes, where they will run through an "edge router." When a cable subscriber served by that hub requests a channel change, the edge router will then send the selected stream to the home over coax and the digital set-top will "join" the multicast session.

The key to switched broadcast for operators, says Taylor, is that customers don’t know what’s actually happening in the background by experiencing a noticeable delay in changing channels.

"They want a transparent consumer experience," he says.

To that end, Scientific-Atlanta was demonstrating a traditional digital cable feed next to a switched-broadcast feed. To this reporters’ watch, the channel change for switched broadcast took about as long as the channel change for a standard feed, a little over two seconds.

Michael Willner, president and CEO of Insight Communications, says that switched broadcast "was one of the more interesting things at the show."

Insight doesn’t have a schedule to deploy switched broadcast yet, says Willner, but it does plan to reclaim analog spectrum by using digital simulcast. Willner expects Insight will probably use switched broadcast as well, but not necessarily in conjunction with digital simulcast.

"I don’t think you necessarily have to do both," he says.