OTHER TECH

"What's Up, DOCSIS?"

Beginning next year, in an effort to compete with high-speed fiber-optic Internet services, cable will roll out a modem technol- ogy, called DOCSIS 3.0, that will enable downstream data speeds of up to 160 megabits per second (Mbps). The technology uses "channel bonding," which combines several 6-MHz channels into a single, larger "virtual" channel. Comcast plans to be the first major cable supplier to offer DOCSIS 3.0 gear. Although the initial target is high-speed Internet access, the faster speeds could allow cable companies to migrate to IP-based video services. DOCSIS 3.0 is expected to let cable companies compete with Verizon, which is moving its FiOS service to new optical hardware that allows downstream speeds of up to 400 Mbps.

Cable companies are turning to ways to expand the bandwidth on existing networks - for instance, by pushing you to view more VOD, where only the requested channel needs to be delivered. They're also moving from the MPEG-2 video format to MPEG-4, which can squeeze twice as much HD content through the pipes without a loss of quality. Other initiatives include channel bonding (see What's Up, DOCSIS?), boosting transmission power, reclaiming (in other words, eliminating) some analog channels, and using statistical multiplexing, where information from several channels is combined for transmission via a single channel.

Cable's biggest potential savior might be "switched digital video" (SDV). Currently, the cable company sends all the programming a customer has ordered to his or her set-top box. But SDV works like VOD, sending only the program that's being watched, instantaneously substituting a different single stream when the channel is changed. This allows bandwidth to be allocated dynamically where needed.

Cox recently said it will use several of these new tools to bump the number of HD channels it plans for this year from the 30 it originally envisioned to 50. Time Warner will have SDV available in at least half of its markets by year's end, and Cablevision has already rolled it out in New York-area systems. As we went to press, Comcast had begun testing SDV in Cherry Hill (New Jersey) and Denver. The efforts appear to be working. Cablevision recently added 15 HD channels from its once-independent Voom service, for a total of 39 HD channels. And Time Warner and Comcast, at last count, had 26 and 23 HD channels, respectively, just a few shy of their telco competitors and ahead of DirecTV.

Telco TV's All-Fiber Diet Thanks to the allure of fiber-optic networks, telco TV has been generating a lot of buzz, luring customers with the promise of unlimited HD content and super-fast Internet access. Still, the fiber juggernaut has moved slowly, mainly because the telcos have to get franchise licenses town by town, much the way cable did when it first became available. But a growing number of states are authorizing statewide franchising agreements (moves being fought, not surprisingly, by the cable companies), which should greatly speed up licensing. Verizon's FiOS service now has about a half-million customers, while AT&T's U-verse has about 40,000. (Both companies also resell satellite-TV services in a number of markets, so the actual number of video users is much higher.)

At last count, FiOS TV was offering 28 HD channels while U-verse had 26. Both services use fiber-optic networks, but there are some key differences. Verizon's is a "fiber-to-the-home" (FTTH) network, meaning that fiber cables are run all the way to a customer's house. U-verse is largely a "fiber to the node" (FTTN) service, where programming is delivered via fiber from the head end to neighborhood nodes - usually within 3,000 feet of customers' homes - and then is sent the rest of the way using existing copper wiring. (But AT&T is running fiber all the way to the home in some new-construction neighborhoods.) Although FTTN is less expensive than FTTH, the latter provides four times more bandwidth, with unshared data streams up to 100 megabits per second (Mbps).

There are other major differences. Whereas FiOS TV uses traditional modulated RF-style video (QAM) for linear broadcast channels and Internet Protocol (IP) for interactive services such as VOD and pay-per-view, U-verse is a fully IPTV-based system. And whereas Verizon uses MPEG-2 boxes for video, U-verse sends linear content in MPEG-4 (H.264) and interactive services like VOD in the MPEG-4 and VC1 (Windows Media 9) formats.

Neither company currently offers HD VOD, but Verizon plans to launch that service this fall. And because it's delivered via IP, it won't have to share bandwidth with the linear TV channels. That's one reason why Verizon can offer 50-Mbps Internet download speeds, while AT&T can spare only 6 Mbps, reserving the rest of its capacity for its IPTV service. And U-verse can send only one HD signal at a time, meaning you can't record one HD show while watching another.