ZigBee is a new technology now being deployed for wireless sensor networks. A sensor network is an infrastructure comprised of sensing, computing and communications elements that allows the administrator to instrument, observe and react to events and phenomena in a specified environment.
Typical applications include, but are not limited to, data collection, monitoring, surveillance and medical telemetry. The administrator typically is a civil, government, commercial or industrial entity. The environment can be the physical world, a biological system, or an IT framework. Sensor networks are seen as an important technology that is expected to be deployed widely in the next few years. For example, observers expect the number of ZigBee-compliant nodes to increase from fewer than 1 million today to 100 million in 2008.
Some sensor networks support highly distributed, large-node-count applications such as environmental monitoring and Homeland Security systems. Others support confined short-range spaces such as a home, factory, building or the human body. Short-range, low-data rate wireless applications include RFID systems, light switches, fire and smoke detectors, thermostats and home appliances. The information collected is typically parametric in nature, where one transmits small volumes of simple data; however, some systems also support low-bit-rate video and imaging algorithms. Node power and battery life are key design considerations for sensor networks.
There are four basic components in a sensor network: an assembly of distributed or localized sensors; an interconnecting wireless network; a central point of information clustering; and a set of computing resources at a central point to handle data correlation, event-trending, querying and data mining. In this context, both the sensing and computation nodes are considered part of the network.
For a number of years vendors have used proprietary technology for collecting performance data from sensors. In the early 2000s device suppliers researched ways to introduce standardization. For in-building applications, designers soon discounted Wi-Fi standards as being too complex and expensive; Bluetooth technology was also considered, but it too was found to be relatively complex.
This opened the door for a new standard, ZigBee (the trademarked name of the IEEE 802.15.4). ZigBee operates in the 2.4-GHz Industrial, Scientific and Medical radio band, and supports data transmission at rates up to 250K bit/sec at ranges up to 200 feet. ZigBee is expected to become a global specification for reliable, cost-effective, low-power wireless applications, providing interoperability and desirable radio frequency performance characteristics. Chip sets implementing the standard-specified protocol stack now are becoming available. Examples of ZigBee applications include lighting controls, automatic meter reading, wireless smoke and CO detectors, HVAC controls, home security, and medical sensing and monitoring. Sensor networks that operate outside a building and over a broad geographic area use any number of other radio technologies; for example, the new WiMAX standard (IEEE 802.16) and cellular 3G technologies also may be useful for metropolitan environments.
ZigBee may well be for you: There will be many opportunities for technology developers in this space in the next few years, as well as for system integrators and network engineers.
Minoli is an adjunct professor in the Stevens Institute of Technology's graduate school and coauthor of a Wiley book on wireless sensor networks. He can be reached at firstname.lastname@example.org.