What is ZigBee
Zigbee is the only complete loT solution â?from mesh network to the common language that allows smart objects to work together. It increases choice and flexibility for users and developers, and makes people believe that products and services will work together by standardizing and testing all layers of the stack.
Zigbee certified products can connect and communicate with each other using the same Internet of things language, and millions of Zigbee products have been deployed in smart homes and buildings. Zigbee is built with backwards & forwards compatibility in mind.
Specification
Frequency
Zigbee operates in the industrial, scientific and medical (ISM) radio frequency bands. Although some devices use 784 MHz in China, 868 MHz in Europe, and 915 MHz in the United States and Australia, even in these regions and countries, commercial Zigbee devices used in homes are still 2.4 GHz. The data rate varies from 20kbit/s (868 MHz band) to 250kbit/s (2.4 GHz band).
Standards
ZigBee V1.0
This is the first public version of the ZigBee standard. It was available for download in June 2005,published on June 27, 2005. The internal file number is 053474R06.
ZigBee V1.1
The second ZigBee standard was available for download in January 2007. The document was published in December 1, 2006 and the internal document number was 053474R13. Also called ZigBee 2006.
ZigBee V1.2
The third ZigBee standard public version was available for download in January, 2008. The release date was January 17, 2008. The internal document number was 053474R17, also known as ZigBee Pro, ZigBee 2007
ZigBee Pro 2015
ZigBee Pro 2015 released in August,2015.It defines a set of rules by which the Zigbee application layer specifications will be created. As such, it provides formal definitions for the common Zigbee terms “Node”, “Cluster”, and “Device”. A Zigbee node represents a single testable implementation.These specifications have been integrated into the ZigBee 3.0 version: this new version eliminates all the problems that slowed down its deployment, offering full interoperability between a wide variety of devices that can now work together and interact with each other within the home.
ZigBee Pro 2017
With PRO 2017, Zigbee is a mesh network capable of operating in two ISM frequency bands simultaneously: sub-GHz 800-900 MHz for regional requirements and 2.4 GHz for global acceptance.
Network
Star
There is only one ZigBee coordinator device per network, which controls the network and is responsible for launching and maintaining the ZigBee network.All other devices are called end devices, can directly communicate with the ZigBee coordinator or other end devices via the ZigBee coordinator. In the Star network, the coordinator becomes a bottleneck for message routing, and failure of coordinator will cause the network to shut down.
Tree
In tree topologies, the ZigBee coordinator is responsible for starting the network and for choosing specific key network parameters, but the network can be extend by ZigBee routers. In a tree networks, routers use tree routing policies to route data and control messages through the network.In Tree network, a router failure can cause the network segment under the affected router to shut down.
Mesh
In a mesh topology, the ZigBee coordinator is responsible for creation and configuration, but the network can be extend using ZigBee routers. Mesh networks allow full point-to-point communication. It also called a self-healing network,means that a coordinator failure does not cause a network failure because the end devices communicate with each other and with the router.
Mesh network is complex and creates a messaging overhead in the network.
Security
Zigbee use a more secure 128-bit AES-based encryption system. The Zigbee protocol is based on the IEEE 802.15. 4 wireless standard, which has two layers, the physical layer (PHY) and the medium access control layer (MAC). Zigbee builds the network layer (NWK) and the application layer (APL) on top of physical and MAC layer. The network layer uses AES-128 to encrypt, and the application layer can also use AES-128.
Feature
- Lower power consumption.
- The data rate is about 250Kbps.
- Network Size (number of theoretical nodes) Up to 65,000
- Security is built in.
- Built-in mesh network support.
- Cross-band communication across 2.4GHz and sub-GHz bands, supporting multiple physical layers.
- Global operation in the 2.4GHz frequency band according to IEEE 802.15.4 protocol.
- Regional operation in the 915Mhz and 868Mhz frequency bands. The transmission range of sub-GHz channel can reach 1 km.
- IP Compatibility.
- Interoperability between different vendors.
- Energy-saving mechanism suitable for equipment.
Advantage
Limitation
Device Type
There are three classes of Zigbee devices:
Zigbee coordinator (ZC): the most powerful device that forms the root of the network tree and can be bridged to other networks. There happens to be one Zigbee coordinator in each network, because it is the device that started the network in the first place. The (Zigbee Light Link specification also allows you to operate without a Zigbee coordinator, making it more suitable for off-the-shelf household products. It stores information about the network, including acting as the trust center and repository for security keys.
Zigbee router (ZR): As well as running an application function, a router can act as an intermediate router, passing data from other devices.
Zigbee end device (ZED): contains just enough functionality to talk to the parent node (either the coordinator or a router). It cannot relay data from other devices. This relationship allows the node to sleep for a long time, thus providing a long battery life. ZED requires the least amount of memory and thus can be less expensive to manufacture than a ZR or ZC.
Zigbee Green Power Device: A self-powering, energy-harvesting device that implements the Green Power feature. Green Power is a feature of Zigbee that allows for energy-harvesting technology to be used directly with the Zigbee stack. Green power is the global wireless standard for large installations, where replacing batteries and access devices become very expensive.
Certification
ZigBee alliance has a certification program for Zigbee device, to test whether the device meet the ZigBee Standards, only certified device can mark the ZigBee logo.
https://zigbeealliance.org/zigbee_products/?product_type=certified_product
Resource
https://en.wikipedia.org/wiki/Zigbee
https://payatu.com/blog/dattatray/zigbee-protocol-101
https://payatu.com/blog/dattatray/zigbee-security-101
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