August 2005

Home Smart Home

Making building-automation practical

By Duncan Graham-Rowe

Next month, a host of new wireless gadgets designed to help make buildings and homes "smart" will debut at the ZigBee Open House and Exposition in Chicago. Among them will be a so-called domestic awareness system that warns you if the stove is left on or if the basement starts flooding. Another lets you network your home entertainment system with environmental controls such as light dimmers or a thermostat. The point of such a setup: to automatically set just the right mood when you're watching DVDs or listening to music.

Underlying these systems is a new wireless-networking standard called ZigBee.

Developed by the ZigBee Alliance -- which includes Honeywell, Samsung, Mitsubishi Electric, Motorola, and some 160 other companies -- the standard allows household appliances, sensors, and other devices to talk to each other without the need for connecting cables.

Of course, this is by no means the first attempt to boost the IQs of buildings and homes by networking their components. So can ZigBee finally deliver home and building automation? Yes, says Chris Ryan, an analyst with U.K.-based Future Horizons who has been following the standard's development.

"The problem in the past is that adding thermostats, lighting controls, and environmental sensors to buildings has been expensive," Ryan says. ZigBee technology could cut installation costs dramatically by letting you install a light switch, say, or a heat or moisture sensor wherever you want in a building just by sticking it on a wall, floor, or ceiling. The device's embedded ZigBee chip -- which costs less than five dollars -- would then link up wirelessly with the appropriate light fixture or alarm, saving the exorbitant cost of installing cables or wires in the wall. This kind of cost savings can make a significant difference both to the owners of large commercial buildings (which is ZigBee's initial target market) and to homeowners.

Whereas many earlier smart systems used proprietary technology, ZigBee is built on an Institute of Electrical and Electronics Engineers (IEEE) global standard, 802.15.4, similar to the standards that govern Bluetooth and Wi-Fi. Open standards encourage innovation and competition, which bring down costs.

But unlike Bluetooth and Wi-Fi networks, which require central hubs that distribute information to dispersed devices, ZigBee allows devices to form mesh networks, where each unit can relay information to its neighbors. Mesh networks are far more robust than their hub-and-spoke counterparts; if a node breaks down, other nodes can automatically reroute transmissions around it. That's a big advantage in something like a building-wide lighting system: you wouldn't want one bum switch to bring the whole thing down. What's more, mesh networking could let ZigBee systems link as many as 64,000 devices; Bluetooth networks, by contrast, are limited to just eight.

Homeowners' first taste of ZigBee is likely to come in the form of adaptors into which lamps, stereos, and other appliances can be plugged. The adaptors, which started shipping this summer,
are activated by wall-mounted wireless switches or even handheld devices, which means you could soon have your whole house on one remote control.