Electronic Design

Waiting For ZigBee

With all of the wireless standards on the books, you would think we pretty much had the wireless front covered. But we don't. We really need a cheaper, simpler, lower-power, longer-range standard that doesn't necessarily need to be fast, and we're about to get it. Say welcome to ZigBee.

ZigBee is a wireless option that can give you practical wireless remote monitoring and control, something you can use in plants and factories, building automation, or home monitoring and control. Some other applications include games, toys, and slow PC peripherals like keyboards, mice, and printers. The current wireless local-area network/wireless personal-area network (WLAN/WPAN) standards such as IEEE 802.11b/a/g and Bluetooth are overkill since they address high-speed data transmission and short cable replacement needs, respectively. Yet the new ZigBee standard is right on target for these simpler, slower speed applications.

ZigBee is designed to operate in one of three frequency ranges: the 2.4-GHz ISM (industrial, scientific, medical) band, the 902- to 928-MHz ISM band, and on 868 MHz. It uses direct-sequence spread spectrum (DSSS) with two types of modulation, depending on the band and data rate. Available data rates include 20, 40, and 250 kbits/s. Typical transmission range is 10 to 20 m with a 0-dBm power level. Distances exceeding 100 meters are possible at lower data rates. As for networking, ZigBee supports both star and peer-to-peer topologies with up to 255 nodes. ZigBee uses the carrier-sense multiple-access with collision-avoidance (CSMA-CA) access method as well.

ZigBee is currently working its way through the IEEE standardization process. Known as 802.15.4, this standard is expected to be ratified in March. For an update, visit www.ieee802.org/15/pub/TG4.html.

Expect to see some silicon and finished products later this year. With Philips Semiconductor and Motorola leading the way, there should be lots of competition, plenty of options, and low prices. ZigBee also has an industry support group, the ZigBee Alliance (www.zigbee.org), with 25 major semiconductor and industrial equipment companies.

If you're designing wireless products for low speed, low power consumption, low complexity, and low cost, ZigBee is worth a look.

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