There are many different choices for IoT devices these days, and there are many different ways to connect to these devices, such as WiFi, Bluetooth, Z-Wave, etc. In this post, I discuss Zigbee—its advantages, disadvantages and applications in home automation.
Zigbee is network protocol based on the IEEE.802.15.4 specification, a standard for low-rate wireless personal area networks (WPANs). Zigbee expands on the IEEE specification by “adding mesh network and security layers along with an application framework to become a full stack, certifiable, interoperable solution."
A Zigbee device typically has four layers—the IEEE.802.15.4 Radio, Zigbee Pro, Zigbee Cluster Library and Zigbee Certification (see below). Zigbee Pro is the network infrastructure, implementing features ranging from communication band specification and pair mechanisms to security key generation and power saving. The Zigbee Cluster Library is the application layer, which is used to define clusters that are standard sets of messages/device behaviors to allow Zigbee devices to behave in a standard manner across devices. This helps with interoperability, so Zigbee devices from different manufacturers can work with each other.
Zigbee devices typically communicate over 2.4GHz, but they can also communicate in sub-GHz bands, which are region-specific. Zigbee can transmit anywhere from 10 to 100 meters over 2.4GHz. It can transmit up to 1km on the sub-GHz bands. Since WiFi also uses 2.4Ghz, Zigbee devices handle interference over 2.4GHz by having 16 separate channels of communication. They also automatically retransmit data as well as send a low number of data packets, making transmission failure unlikely.
Zigbee is interoperable, which means that if I buy two different Zigbee devices, they're capable of communicating with each other over the Zigbee network. While there are limits to interoperability due to multiple application profiles, such as Home Automation and Smart Energy, Zigbee's device interoperability is still a very useful feature.
Zigbee is capable of forming various arrangements of networks, or network topologies, between its devices. The most common network topologies are shown below—star, cluster tree and mesh. Each Zigbee network can consist of three types of devices: end device, router and coordinator. A coordinator is responsible for creating the network as well as routing traffic through it. A network can only have one coordinator. A router is responsible for routing traffic, and an end device does not route traffic through the network. (Silicon Labs and Elprocus).
Finally, Zigbee’s main advantage over another network protocol like WiFi is that it's very low-power. This is a result of it being IEEE.802.15.4 standard plus the Zigbee protocol itself mandating lower power operation. While this does mean that Zigbee devices may not have a high range or push through much data, they do save power, money and maintenance work. Zigbee even has a Green Power feature, which allows battery-less devices to join the network. According to the Zigbee Alliance, “Green Power [can take] advantage of the energy used to flip a typical light switch via common energy harvesting techniques, which is powerful enough send commands through a Zigbee PRO network.”
Now that we have understood what Zigbee is at a high level, let’s look into Zigbee’s application for Home Automation. Zigbee is ideal for home environment becomes out of the box with a mesh network and most devices should be within the 10 to 100 meter range of each other. It is nice to know that you can go to the store buy an entirely new Home Automation Zigbee device and it will connect into your existing mesh network. Currently the Zigbee Alliance site lists about 400 devices for Home Automation. The Home Automation Zigbee Devices are all the common IoT Home devices such as light bulbs, switches, locks, motion sensors, and thermostats.
There are major companies with Zigbee products including Samsung, Bosch, Honeywell, Texas Instruments and Amazon. In fact, Amazon’s Echo Plus came with a built-in Zigbee hub to control Zigbee devices. Samsung’s SmartThings devices uses Zigbee as well to communicate (they also support Z-wave). It's good to see that Zigbee has support from big-name companies and a wide-range of devices.
In conclusion, Zigbee is a low-power low-data network protocol. Zigbee devices can easily be added to a network such as mesh network to communicate with each other. It's ideal for applications such as home automation, where devices don't communicate frequently and are in close range of each other. Zigbee’s built-in power saving is a great feature that allows devices to last on battery much longer than other network protocols. I hope you all try Zigbee devices to automate your homes!
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