Touted as a low-cost, low-power, low-data-rate technology, Zigbee is already getting attention from potential customers. They range from industrial control and home automation companies such as Honeywell, Eaton and Invensys Metering Systems to toy companies like Mattel.

All have participated in the IEEE 802.15.4 group responsible for developing technical specifications for Zigbee's physical and media-access control layers.

The blue-chip companies "have been very vocal in the standard development and they are telling us what they want us to do," said Kristen Law, senior product-marketing engineer for wireless connectivity at Motorola Inc.

The draft spec is on track to be refined in a third round of balloting later this month. The final spec is expected to be ratified at the end of the year.

Though IEEE is churning out wireless standards at a rapid clip, Zigbee proponents say theirs is unique in that power consumption is so low that it allows a battery to last many months to years.

Backers also say it will cost less than $2 to implement Zigbee in a system, making it inexpensive to install more nodes in a network.

Zigbee protocols are said to be simpler than those of Bluetooth, high-rate personal-area networks (PANs) or 802.11x wireless-LANs.

Philips Semiconductors will finalize Zigbee's system spec and evaluate system development by October, said Francisco Ferrer, product line manager for wireless PANs. By March, Philips will provide samples of its first one-chip Zigbee solution integrated with radio and baseband, he said.

For its part, Motorola plans to offer a complete 2.4-GHz Zigbee system that includes an RF transceiver and a choice of 8-bit microcontrollers that will contain the application stack for both full- and reduced-function devices, as required by 802.15.4 specs. The company expects to roll out the system in the second half of 2003.

Zigbee has its sights trained on industrial and home automation applications such as factory floor systems, crop sprinklers or household thermostats. Beyond that, proponents are hoping to widen its appeal to makers of toys, game machines, consumer electronics devices and PC peripherals.

This agenda is decidedly less ambitious than that of existing wireless-networking schemes, such as Bluetooth, which have been slow to emerge.

"We do not want to create an expectation that we cannot fulfill," Ferrer said. "Bluetooth's two-year delay was very upsetting to a lot of companies."

A number of wired and wireless solutions — including infrared narrowband 27-MHz through 900-MHz RF transmission — address Zigbee's target area, but no one agreed-upon method exists.

"This lack of standardization leads to higher expense for the end user, especially in terms of development cycle time," said Motorola's Law. The user "would need to develop its own RF protocol link-management software."

Not like Bluetooth

One of Zigbee's most notable attributes is low power consumption.

"Battery-operated devices are an area where the differences between Zigbee, Bluetooth and wireless LAN are very apparent," Law said. "The Zigbee chip set can be held in 'hibernate' mode until an external event triggers an interrupt." In this state the Zigbee system will draw a few microamps, against 100 microamps or more for a comparable Bluetooth state and tens of milliamps for wireless LANs, she said.

Once Zigbee starts showing up in consumer electronics equipment and PC peripherals, the inevitable question is how it will coexist with Bluetooth.

Ferrer, who is responsible for both Bluetooth and Zigbee products at Philips, believes the lines of distinction are clear. "Bluetooth won't be used in home automation applications, while Zigbee will not be incorporated in cell phones and headsets," he said.

Cost is another deciding factor. Ferrer predicted that a Bluetooth system solution, which costs somewhere between $7 and $10 today, may go as low as $4 next year. "It's most likely that Bluetooth's cost won't get much lower than that," he added. In contrast, by 2004 a Zigbee solution will come in at "less than $2," he claimed.

As Motorola's Law pointed out, Zigbee's RF link protocol and customer application are hosted in an 8-bit microcontroller, whereas Bluetooth requires a dedicated core to manage the baseband protocol stack and a separate host device to manage the Logical Link Control and Adaptation Protocol, RFCOMM, protocol interfaces and applications.