Wireless sensor networks looking to Zigbee Alliance

Imagine a golf course that can sense rainfall, and adjust the automatic sprinkler system to delay a scheduled watering session or focus on parts of the course that didn't get as much rain as others. Or a hotel that can detect when a room is vacant, and turn off the heating or cooling systems in that room to save energy.

Later this year, vendors will start releasing products based on a wireless standard called Zigbee that enable these types of sensor networks. The Zigbee Alliance planned to certify products with a Zigbee logo to ensure that products from different vendors were interoperable and easy to manage, chairman of the Zigbee Alliance, Bob Heile, said.

Zigbee is a set of networking, security and application software standards that sits atop the 802.15.4 low-data wireless standard approved by the Institute of Electrical and Electronics Engineers.

Unlike other wireless standards such as 802.11 or 802.16, Zigbee and 802.15.4 were designed to carry limited amounts of data at a maximum rate of 250Kbps (bits per second), Heile said.

Backers of the technology take great pains to avoid overselling Zigbee as a wireless panacea, but many think the technology can find a home as a replacement for wiring that connects electrical system controllers or passive asset management tags.

Zigbee will allow users to construct mesh networks that can send data back to a central repository, respond to changes in their environment and monitor themselves for failures or redundancies, director of radio technology and strategy at Freescale Semiconductor, Jon Adams, said. Other popular wireless standards are overkill for the types of applications envisioned by Zigbee supporters.

Wi-Fi and Bluetooth used far more power than a Zigbee radio would consume, Heile said.

The Zigbee Alliance thought radios built with the standard should be able to operate on standard household batteries for years, he said.

Wi-Fi and Bluetooth chips were also much too expensive to justify setting up the large networks that would allow some of these applications to work, an industry analyst with Meta Group, Jack Gold, said.

Semiconductor makers, such as Freescale, would have to produce chips that cost less than $US1 to convince companies that there was a need for this type of information.

After addressing the cost issues, Zigbee products should be an easy sell to any factory or distribution outlet that wants to assimilate as much information as possible, president of Harbor Research, Glen Allmendinger, said.

Most businesses develop operations or capacity plans using historical data that only presented users with a sense of what had happened in the past, Allmendinger said. Sensor networks would allow companies to gather data as it happens, and therefore predict where problems might occur.

For example, a Zigbee tag could be placed on a pallet of chocolate bars and provide more data than whether that pallet arrived at its destination, Adams said.

These tags could tell the chocolate manufacturer whether the temperature around that pallet had risen steadily for the past hour because it was left on a runway in the sun. Armed with that data, the manufacturer could call the airport and have that pallet moved before its merchandise melted away.

Some companies were starting to experiment with passive radio frequency identification (RFID) tags that did little more than store a unique identification number.

Zigbee radios held some promise as active RFID tags that could sense more complicated information and distribute that information on its own, president of the Wireless Data Research Group, Ian McPherson, said.

"[Zigbee products] are not meant to replace passive RFID, but they can change the economics of active RFID by using more sensors and less gateways," McPherson said.

Right now, even passive RFID tags were too expensive for most companies to consider implementing, but costs were expected to come down over the next few years, he said.

Despite Zigbee's promise, the technology would face hurdles as users tried to scale their networks to massive sizes, McPherson said.

Mesh networks were an emerging technology that users were still evaluating and troubleshooting, he said.

The technology would probably be used on less-important applications until users became comfortable with the technology, McPherson said. Freescale would introduce Zigbee-based products in the fourth quarter, Adams said.

The company is a promoter of the Zigbee Alliance along with companies such as Samsung Electronics, Honeywell International, Ember, Philips Electronics, Mitsubishi Electric and Invensys.

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