In a couple of years' time, we will be turning on our lights and monitoring our home security by remote control. But will we be using the much-lauded Zigbee standard? Or could other protocols steal its market?

Zigbee has the air of a done deal. A short-range low-bandwidth network, developed by a major alliance of vendors (the Zigbee Alliance), and running over an established standard (IEEE 802.15.4) in unlicensed spectrum, it has a major major opportunity as homes and factories connect up sensors and devices by wireless.

However, it has competition, and its rivals talk big. "Zigbee is dead in the home space," says Chris Johnson, vice president of business development at Zensys, the company behind a rival called Z-Wave. While Zigbee aims to do everything, says Johnson, rivals like Z-Wave can take chunks of market away, removing the economies of scale on which Zigbee's success is predicated. "The Zigbee market is much smaller than the Zigbee Alliance claims," says Johnson.

Pick a better band?
While Zigbee majors on the unlicensed 2.4GHz band, home of Wi-Fi and Bbluetooth, Z-Wave operates in unlicensed bands around 800MHz, used in various countries for cordless phones, which Johnson says is a better fit for control applications, particularly in the home.

"2.4GHz has too much bandwidth for control applications," says Johnson. "It has less range, requires more power and is a more crowded band." For the small messages that are required to switch devices on and off, and gather information from sensors, 800MHz is perfectly adequate, he says. "Sub-GHz signals have 30m range indoors, and 500m outside."

In that band, Zensys has re-used the FSK radios developed for cordless phones, and delivered volume silicon in April. Like Zigbee, Z-Wave systems set up a self-healing mesh network, passing signals between themselves.

Nodes are dedicated to one network, and can only be added in proximity to the controller, to ensure networks remain secure and do not interfere with each other. Traffic is encrypted to prevent snooping and attacks which playback network traffic.

Sensors and switches are available, and companies including Honeywell are on board. Z-Wave enabled home management software such as Meedio Housebot and HomeSeer is appearing. "Home automation by Z-Wave is a done deal in the US," says Johnson.

Z-Wave problems
The fly in the ointment is the fact that Z-Wave is proprietary. : Zensys has set up a user group, called the Z-Wave Alliance, but Zensys makes the only modules.

"It's proprietary and has about 5 percent of the functionality at similar price points," says Bob Heile, chair of the Zigbee Alliance. "They will have their fifteen minutes of fame but will ultimately be marginalised by a larger volume of suppliers who can buy solutions from multiple silicon vendors."

If the sub-GHz bands turn out to be better, it's no problem, says Heile, as Zigbee also has a sub-GHz version, which has been implemented in products: "Zensys can only access 30 percent of the world market. the low band. Zigbee can access 100 percent."

Even the freedom from interference is disputed, with Heile claiming that even a single cordless phone can disrupt Z-Wave in the 900MHz band, where it is, he says, single band.

Everything in the Zigbee garden is rosy, according to Heile, who earlier this month presided over a Zigbee "open house" in Chicago, which featured products from thirty vendors, including a low-power system from Ember and Texas Instruments, already in use for monitoring the health of the elderly in Virginia, and a single-chip Zigbee device from Oki, as well as another from Chipcon which includes networking and 128k of Flash memory.

But there's more competition
Whatever the merits of Z-Wave, there are other contenders lining up against Zigbee. Some of them have come from the existing home automation space, and some implement different upper-layer protocols on top of 802.15.4.

One that has had positive response from analysts is Insteon, a system that is backwards compatible with the existing X-10 radio control sysatems. "Insteon being fully backwards compatible with X-10, has a strong advantage," says analyst Kirsten West of West Technology Research Solutions, "in that it can piggyback on the X-10 installed base and can in addition also port onto any 802.15.4 compliant chip for the wireless component of the solution."

Analysts tend to be sceptical of Zensys' long term prospects, for its lack of an IEEE basis. "Z-Wave has no underlying IEEE standard," says Harry Forbes, senior analyst at the ARC Advisory Group. "The competitors for ZigBee are proprietary solutions using IEEE 802.15.4, that offer different performance parameters, plus to some degree other technologies like 802.11 and Bluetooth, and also future developments."