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.
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