Zigbee is a high level communication protocol for small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs). Zigbee is specifically useful for applications that require a low data rate, long battery life, and secure networking.

A wireless personal area network (WPAN) is meant to cover a small area like for instance a home, where communication is needed over relatively short distances. One of the key aspects of WPANs is ad-hoc networking, which means that devices can be part of a network on a temporary basis. Zigbee is known as a sleepy, battery powered WPAN that would be a perfect fit for wireless sensor networks for applications in agricultural, building and industrial automation and home control.

Zigbee is specified by the Zigbee Alliance, which is backed by a large number of suppliers. So called profiles are specified for several market segments: Energy Management, Health Care, Building Automation, Home Automation etc. These profiles specify the devices for these markets and the so called clusters which are applicable. A cluster is a set of commands and attributes that can be used to control and interrogate the devices. All clusters are part of the Zigbee Cluster Library (ZCL).

I have been playing with XBee hardware for some time, but found the supplied stack not very usable for Home Automation (ZCL not supported). TI offers a far better hardware platform for this purpose. I finally bought hardware modules (Z100A) from NetVox, which are based on the TI CC2530. I have used these modules as a base for my DIY hardware Zigbee modules.

Some Zigbee characteristics:

  • Frequency: 2.4 GHz
  • Physical Standard: IEEE 802.15.4
  • Range: 30-100m
  • Current: 3 uA asleep, 30-60 mA while transmitting
  • Data rate : max 250 kbps
  • Network join time: 30 ms
  • Nodes per network: 64000
  • The Zigbee specification adds support to the IEEE 802.15.4 standard for the mesh and cluster tree network topologies. After a device has joined a Zigbee network, it can send commands to all the other devices on the same network.

Zigbee device types
All Zigbee devices can be divided into 3 types.

Zigbee Coordinator (ZC)

  • This is the only device required for creating a ZigBee network
  • It initiates network formation
  • There's always only 1 coordinator in a ZigBee network

Zigbee Router (ZR)

  • This is an optional component
  • It may associate with the ZC or a ZR
  • Takes care of it's ZEDs regarding routing data

Zigbee End Device (ZED)

  • No routing capability (Note: A ZED can also have routing capability, but should not enter a sleep state than)
  • Low power operation
  • Used as sensor/actuator

Advantages of Zigbee

  • Based on open standards and detailed documentation is freely available
  • Vendor independence, no proprietary solution
  • Its network is reliable and self healing
  • It's easy to use (all the hard work has been done for you 'inside' the firmware)
  • It's secure (encryption)
  • It supports a large number of nodes
  • It enables long battery life
  • It's low cost