ZigBee protocol

The ZigBee protocol is a communication protocol defined by the IEEE 802.15.4-2003 standard. The protocol uses small, low-power radios to create Low-Rate Personal Area Networks. Zigbee devices offer a low data rate, but with reliable data transfer, secure networking, and low power (and hence long battery life), and at a low cost. It is used as the basis for the popular XBee modules for Arduino.

Technical Details
Zigbee has a number of released specifications, and several more under development:


 * ZigBee Home Automation
 * ZigBee Smart Energy 1.0
 * ZigBee Telecommunication Services
 * ZigBee Health Care
 * ZigBee Remote Control
 * ZigBee Smart Energy 2.0 (Under Development)
 * ZigBee Building Automation (Under Development)
 * ZigBee Retail Services (Under Development)

The ZigBee specifications is publicly available for free. Entry level membership in the ZigBee Alliance (Adopter) provides access to unpublished specifications and permissions to to use the specifications in commercial applications.

It operates in the ISM radio bands (868MHz in Europe, 915MHz in the USA and Australia, and 2.4GHz is most world-wide jurisdictions). Sleep-to-active time ranges about 15ms, offering low latency. Likewise, the device is designed to remain largely in sleep mode, greatly extending battery life.

There are three different classifications of ZigBee devices:  ZigBee Coordinator (ZC): The Coordinator is the network root, and has the potential to bridge to other networks. There will be only one Coordinator. ZigBee Router (ZR): Can run processes but can also pass data to other devices. ZigBee End Device (ZED): Can talk to a parent node, but cannot relay data between other nodes. 

Protocols
There are two types of ZigBee networks: Beacon and Non-Beacon.

In a Beacon Network, WigBee Routers transmit beacon signals to alert network nodes to their presence. To save power, nodes only need to be active while a beacon is transmitting. In Non-Beacon networks ZigBee Routers are constantly active, thus requiring more power. This allows some devices to constantly receive while other devices only transmit periodically.

Links

 * ZigBee Alliance