At the main gate. (powering residential broadband networks)(Cover Story)

Powering the full service network.

In a Ray Bradbury story, an automated "smart house" operates flawlessly after a doomsday machine wipes out all human traces. Robots carry out their chores, making coffee and asking questions of silent masters. Eventually, though, the house loses power and goes "mad": electrical flaws catch up with the robots' misguided actions; time weaves its tapestry of shorts and blips, and the house burns to the ground.

The sci-fi allegory has some relevance to the powering of today's residential broadband networks. Fire, lightning, heat and increased power consumption are concerns for typical hybrid fiber coax (HFC) networks. As HFC, various digital subscriber line (xDSL), fiber-to-the-curb (FTTC) and other broadband networks proliferate, alternative copper and fiber solutions must be devised as functions traditionally performed in the central office move toward customer premises.

"The powering issue for broadband is still in its infancy," says Paul Pishal, a director of technology systems planning for Scientific Atlanta, producers of the "MainGate" energy management system for residences ["Opening Up the Residential Gateway," AN, Oct. 1, 1996]. People enhance the ability to provide power not only for adequate backup, but for reliably monitoring data that comes back from individual homes, he says.

Full-service telephony adds a power requirement to HFC, and not always in the most efficient or elegant ways. "The major element that impacts power is the telephony device, and if that's expected to be powered from HFC networks, it puts quite a burden on the system," says Chuck Dougherty, marketing vice president for transmission network systems at General Instruments. "A typical HFC system that comprises about 500 homes in the serving area, or about 100 homes per mile, works out to be somewhere around 2.5 watts per home passed in power consumption. That's excluding telephony products. Depending on whose ... products you want to implement, that can impact power draw anywhere from 5 to 7 watts per home passed.

"Most customers aren't concentrating on 100% telephony penetration, either," Dougherty adds. "Consequently, they're powering for lighter loads than 100% and …