One of the emerging applications of WSN is wireless monitoring and control. ZigBee is such an application that uses low-power and low-data-rate networked sensors. It was developed by the ZigBee Alliance, an industry association of semiconductor companies and network equipment companies such as Ember, Honeywell, Mitsubishi Electric, Motorola, Samsung, and Philips. It has to be noted that the term ZigBee refers to the silent communication between honeybees where the bee dances in a zig-zag pattern to tell others the location, distance, and direction of some newly found food. WSN communication somewhat resembles the ZigBee principle in that they must be simple and effective.
The idea is to take advantage of wireless sensors to monitor environments, objects, and human beings and control devices, appliances, and facilities. Wireless sensors make it possible to remotely and conveniently monitor or be notified of operational states or crucial state change of an object, such as a dying battery in a smoke detector and rapidly increasing temperature in a truck carrying frozen goods. WSNs in ZigBee are not designed to carry large data transfer due to the limited capability of wireless communication; however, these sensors are able to form a fully functional network, self-organize for efficient data routing and in-network processing, and self-heal in the case of node failure. The initial target markets of ZigBee products are home control, building control, industrial automation, personal healthcare, consumer electronics, PC and peripherals control, etc. Key specs of ZigBee include the following:
» Frequency bands: 868 MHz, 915 MHz, and 2.4 GHz;
» Data transfer rate up to 250 Kbps;
» Signal transmission range of 10 to 100 m, depending on the sensors being used;
» AES encryption of data;
» Various ZigBee applications can work with each other;
» Low power usage.
Unlike UWB or Bluetooth, ZigBee specifications do not define radio interface and data-link layer protocols; ZigBee simply uses the IEEE 802.15.4 physical radio standard. The ZigBee network application support layer and application profile are the major components that make up the ZigBee specification. Because ZigBee is a proprietary protocol rather than an open standard like those ratified by IEEE, its fate hinges on how it refines itself to become the de facto industry standard. To this end, standardization battles seem inevitable.
Source of Information : Elsevier Wireless Networking Complete 2010