How large can a ZigBee network be? In a few years, a typical house might conceivably have 100 or more devices, while a large office building or factory could contain tens of thousands of ZigBee nodes. Theoretically, a single ZigBee network might address more than 1018 devices, though 65,000 is the limit imposed by IEEE 802.15.4.
At the bottom of the ZigBee network hierarchy is a type of node called a ZigBee End Device (ZED), which can perform only a single monitor or control function. The ZED communicates with nodes called ZigBee Routers (ZR). These can perform monitoring or control tasks, but they can also function as a router or repeater to pass a message along to another ZR or to the ZigBee Coordinator (ZC). Each network has one single ZC, which initiates the network formation.
Each ZigBee device includes the radio along with an embedded controller, the IEEE and ZigBee stacks, and minimum memory (both RAM and ROM). All can be created using low-cost, 8-bit microcontrollers that are battery powered.
ZigBee was designed from the start to use very little electrical power. In general, ZigBee protocols do this by minimizing the time the radio is on.
In most devices and applications, users will expect battery life that's measured in years. For applications with very low duty cycles -- such as automated meter reading, where a device is active less than 1% of the time -- battery usefulness may be limited only by the battery's own shelf life. This could mean the advent of single-chip devices that automatically transmit data when needed and run for years. For some types of devices, it may be most appropriate to replace the entire unit, not just the battery. The potential for medical or environmental monitors is extraordinarily bright.
History
The idea for ZigBee started in the late 1990s, when many engineers realized that both Wi-Fi and Bluetooth would be ill-suited to many applications. In particular, many engineers wanted to design ad hoc networks of digital radios that could organize themselves without requiring external configuration or network administration. The IEEE 802.15.4 standard was completed in 2003 and ratified in late 2004.
The ZigBee Alliance (www.zigbee.org) is an industry association that has branded and is promoting new uses for this wireless networking standard, in a fashion similar to how the Wi-Fi Alliance has pushed the Wi-Fi standard. Formed in 2002, the alliance coordinates activities and regulates and promotes the proposed standard and related technologies. More than 175 companies have joined the group.
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See the complete Faces of Mobile IT special report.
Kay is a Computerworld contributing writer in Worcester, Mass. You can contact him at russkay@charter.net.
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The Faces of Mobile IT
Different types of mobile workers, such as road warriors, telecommuters and blue-collar workers, need different forms of IT support.
Stories in this report:
- Editor's Note: The Faces of Mobile IT
Editor's Note: Corporate America is addicted to mobile connectivity. In this special report we hear the stories of different types of mobile workers -- the devices they use, the features they'd like -- as well as the stories of the IT workers who have to support them. - Wireless Worker: White-Collar Road Warrior
These road warriors are savvy wireless users, which in turn creates support issues for IT. - Tethered to Treo
- Lightening the Load With Data Sharing
- Wireless Worker: Globe-Trotter
Different protocols, standards and security issues create unique support issues for workers who skip from country to country. - Wireless Worker: Blue-Collar Worker
In choosing portable devices for use in the fields, IT must find one that has the right technology, is sturdy enough to handle tough working conditions and comes at the right price. - At Home With a Palm
- Wireless Worker: Telecommuter
Stay-at-home workers are powered by laptops sitting atop docking stations, cordless phones outfitted with voice over IP and the often-mandatory instant messaging. - Close Contact With IP Communicator
- Wireless Worker: Campus Nomad
Most workers who spend their days roaming corridors and campuses want high connectivity paired with low-tech mobile devices. - PDAs for Warehouse Support
- Wireless Worker: Call Center Agent
Voice-over-IP and wireless and computer telephony integration options are making it easier to set up call center agents to work at home. - Setting Up Security With a 'Locked-Down' PC
- QuickStudy: ZigBee
ZigBee is a short-range, low-power, wireless personal-area network technology optimized for low-cost sensor and control devices used in homes, office buildings, and medical and industrial settings. - The Real Magic of Wireless Technology
Your end users expect real-time data anywhere they happen to be. It's your job to make that magic happen, says columnist Mark Hall. - Research Insights
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Online Exclusives
- Cool Wireless Stuff.
Sure it may be practical and help improve efficiency. But what good is a wireless gadget if it's not fun? Computerworld staffers share some of their favorites, from a universal charger to a $1,200 digital sound system. - The War Driver Returns:
Computerworld's David Ramel hits the road again to check out the state of wireless security — and comes up with some surprising conclusions. - Executive Briefing:
Read about the threats from mobile and wireless technology in the enterprise, and the strategies developed to deal with them, in this online special report. - Lone Warrior:
What about the one-person shop? Learn how power PDA user Bert Latamore thrives on being completely mobile and self-sufficient — until there's trouble. - The Wireless Security Value Chain
Click here to view this webcast.
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