Zigbee is a word that has become almost synonymous with the Smart Home, but how does it actually work and what are some of the upsides and downsides to using Zigbee in our Smart Homes?
Let's find out as we explore the Smart Home Protocol of ZigBee!
How Does ZigBee Work?
Unlike WiFi that we looked at in the previous article, ZigBee is a protocol that was designed specifically for low power wireless applications like consumer electronics, medical equipment, industrial automation and you guessed it - home automation.
However, just like WiFi, Zigbee also operates in the 2.4ghz radio frequency space, but that doesn’t mean its characteristics are the same - far from it.
ZigBee Coordinators and End Devices
Zigbee is a wireless mesh network, where you have two different types of devices, a ZigBee Coordinator and a ZigBee end device.
The ZigBee End Device are usually battery operated devices such as motion sensors, and these communicate back to the ZigBee Coordinator.
The ZigBee co-ordinator is a mains powered device responsible for starting the ZigBee network initially - there can only be one Coordinator in a ZigBee network.
It receives information from the end devices, and is responsible for converting this information into a format that computers and our phones can actually use, by bridging it to our home networks, since our phones and other devices cannot speak ZigBee natively.
So far, that sounds pretty straight forward and similar to WiFi right?
The ZigBee Router
That’s where our third type of device comes in, the ZigBee Router. Not to be confused with the WiFi router - leave it to the tech industry to keep using confusing names for stuff!
The ZigBee router is a special device on the ZigBee network which helps it with its mesh capabilities - this is a mains powered device or sensor such as a smart socket or light switch, and just like our battery operated devices, can also send information to the coordinator - but this time, can actually route data packets from those other devices, to the coordinator.
This is a game changer for ZigBee, because it means that ZigBee End Devices that would otherwise be physically out of range, are able to connect and join the ZigBee network, through the ZigBee router.
They are also particularly useful for adding overall strength and reliability to a ZigBee network, since you can have many routers in a single ZigBee network, all of which can provide extra pathways for data packets to travel down, great for if another router ever goes offline.
Joining A ZigBee Network
ZigBee devices can join a network by first placing the coordinator in pairing mode, then pressing and holding the pair button on the end device and after a few seconds the device will join the network. ZigBee also implements AES128 bit encryption to help secure the network.
ZigBee - The Pro's
So that is how ZigBee works in a nutshell, but what makes ZigBee one of the most popular smart home protocols out there at the moment?
ZigBee's first upside is WiFi's biggest downside - battery life.
ZigBee was designed with low power applications in mind, and it certainly delivers on that promise - usually the biggest draw of power with wireless applications is having a radio on and powered on.
ZigBee minimizes this by allowing end devices to turn off the radio when the device is not transmitting, a feature that is not possible with a WiFi network and means that a lot of ZigBee devices spend most of their time asleep.
This is huge for saving power, and the net result is that some ZigBee devices can last for well over a year on a single battery.
Take a look at this video from The Hook Up, which shows a ZigBee door sensor lasting for over 878 thousand cycles before the battery ran out - that’s a lot of opening and closing the door!
Cost And Availability
ZigBee is also an open standard, which makes it low cost compared to some other standards.
It also means that because anyone can use it, there is thousands of different ZigBee devices out there on the market - everything from motion sensors and contact sensors, to door locks, sirens, smoke alarms and everything in between.
If you are looking for a smart home device, chances are you will probably find it available in ZigBee format.
ZigBee's other huge advantage is as we spoke about earlier, is its mesh capabilities which can really help improve the overall distance and reliability of the network.
By adding additional devices that will act as ZigBee Routers, that, as well as improving the ZigBee network, can also be used to benefit your smart home as a whole - WiFi can also be extended by adding more access points, but this would generally be far more costly not to mention time consuming than extending a ZigBee network would be.
ZigBee - The Con's
ZigBee so far is sounding pretty amazing right, it’s relatively cheap, has a wide range of available devices, works great with battery powered devices and has mesh capabilities, but it's not all sunshine and rainbows and there are some downsides to the ZigBee protocol.
Single Failure Point
Let's start with that last one, the mesh capabilities - remember earlier I said that you can add as many ZigBee routers as you want, but there can only be one ZigBee coordinator for the network?
Well that ZigBee Coordinator is a potential failure point for the entire network - should that coordinator fail or go offline, then the whole ZigBee network is dead in the water.
And it's not like with WiFi where you can just replace a dead access point and all the devices will reconnect - if you are forced to replace a dead coordinator, none of your ZigBee devices will automatically reconnect, they need to be manually re-paired again before they will work.
ZigBee can also suffer from some rather unfortunate compatibility issues - ZigBee started out as an open standard with great intentions for inter-compatibility between devices and manufacturers. But that open nature unfortunately became its downfall when manufacturers took that open standard and twisted it into something to fit their own needs.
That resulted in a very fragmented ecosystem where one manufacturers ZigBee hub, or Coordinator, will only work with that brands devices and sensors and this is arguably the biggest problem with ZigBee, is you never know if it will place nice with another device.
Now there have certainly been huge strides to combat this problem, such as community websites that list individual device compatibility, or software that can force devices to work together properly, but this only really helps users of opensource platforms like Home Assistant or OpenHAB.
ZigBee 3.0 has also been a big help here too by requiring manufacturers to implement the protocol in a standard way before they can be certified, but even though ZigBee 3.0 was finalized in 2015, we are only now starting to see ZigBee 3.0 devices become more popular now after the damage was done.
Finally, you know how ZigBee is great for battery devices because of its low power consumption?
Well not only is the power consumption low, but so is the bandwidth. ZigBee tops out with a theoretical max of around 250 kilobits per second. Now don’t confuse low bandwidth meaning that ZigBee is slow, far from it.
ZigBee is generally very quick to respond when it needs to be and is perfectly suited for most devices and sensors since they aren’t high bandwidth applications, the only real limitation of its low throughput is that it makes it unsuitable for video applications like doorbells or CCTV cameras - both of which would be much better suited using WiFi anyways.
Should You Use ZigBee In Your Smart Home?
What is the final decision on ZigBee, and is it worth considering for use within our smart home?
Absolutely - ZigBee is a great smart home protocol that has many good things going for it and is definitely worth considering so long as you're aware of some of its limitations that we just talked about, but overall, ZigBee is an absolute staple in the smart home world.