What is Zigbee and what is its importance to IOT?

Zigbee is an open global wireless protocol standard that addresses the needs of low-cost, low-power networks that connect IOT devices such as home automation; (automating functions like opening doors, garage openers, water sprinklers, etc.); environment control like temperature; controlling traffic; and other IOT devices and not just home automation. The range is around 10 to 100 meters and a Zigbee  network can support 1000's of end devices.

 

Technically speaking the Zigbee standard operates on IEEE 802.15.4 (physical and MAC layers)  physical radio specificaiton and operates in unlicensed bands 2.4GHZ, 900MHZ and 868 MHZ (http://www.rfwireless-world.com/Tutorials/Zigbee-frequency-bands-data-rates.html).

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The Zigbee protocol was been created and ratified by member companies belonging to the Zigbee alliance consisting of more than 300 leading semicondutor manufacturers; technology companies; service providers; and OEMS. You can find the member list here: http://www.zigbee.org/zigbeealliance/our-members/

Zigbee components:

• Coordinator
• Router
• End device

The componets are connected in mesh or star. The coordinator which is installed first  as well as the routers which join the Zigbee network next are always up and the end  devices (bulbs, thermostats, etc.) that join later can stay up or down. The end devices are usually battery operated.

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Here is an example of setting up a Zigbee network with a specific device. network.
http://www.solaredge.com/files/pdfs/se_application_zigbee_gateway.pdf

Zigbee being open stardard, the adoption will be slow and vendors add their own special tweaks. Xbee is a special kind of Zigbee manufatured by Digi International. Review this link for more info on Digi and IoT(www.digi.com).