​Thread, ZigBee, Z-Wave: Why smart home standards matter

We explain what's going on behind the scenes

Wi-Fi has proved to be a really effective way of getting our laptops, our tablets, our phones and even our TVs and stereo systems to talk to the internet but it's not working for the smart home.

The Internet of Things has more subtle needs than these big-batteried, regularly charged or permanently powered items, and clunky old Wi-Fi can't handle the pressure of getting scores of small sensors talking.

Essential reading: Check out our smart home hub

You might have heard of names ZigBee, Z-Wave and, more recently, Thread but what do they do? And should be you considering them when planning your smart home? Read on to find out.

Why standards matter

Let's say you fill your home with connectable devices. They're sitting there - your washing machine, your door lock, your toasted sandwich maker or whatever - and they're bursting with notifications to send to you and to each other.

For that to happen, we need to make sure that they're all talking the same wireless language on the same frequencies otherwise they'll never be able to communicate.

A wireless standard, in this instance, is therefore a single technology that all the manufactures can agree to embed into their smart home gadgets to make sure there's homogeneity. That way, you can rest assured that when you buy product X, it's going to work with products Y, Z and the rest of the alphabet. That's the idea but the trouble is that not everyone has agreed on what that standard is going to be, and in all likelihood, they never will.

What about Wi-Fi?

Wi-Fi is the name of a wireless standard that is really good at providing wireless internet access for your TV, your laptop, your phones and tablets but it's not the best answer for all situations. The very existence of Bluetooth and NFC should be proof of that if nothing else.

Wi-Fi takes a lot of processing power, it runs down batteries relatively quickly and its range isn't always the best. For products which are mains-powered or those which we're used to recharging overnight, then that's ok but it's not a realistic option, for example, for all the little window sensors that help make up your smart home security system. You can't plug them all into the mains or change their batteries every day and the ones at the extremities of your house will be out of reach of the network.

What we need from a more universal wireless standard for the smart home, then, is something with good range, low power requirements, high capacity and very robust. Wi-Fi is ok but it doesn't fit the bill entirely.

Who's using what?

Bluetooth is a solution of sorts, although, like Wi-Fi, not a complete one. It's very low power but it's also very low range. So, while you could still have battery operated kit, it would need to be very close to the rest of the network which, more often than not, isn't going to be convenient. On top of that, there are limitations with the number of devices that you can connect together using Bluetooth and that pairing itself is not as automatic or convenient.

The two most common smart home wireless standards are called ZigBee and Z-Wave and both have been around for about 10 years now. Like Bluetooth, they have the kind of low power consumption that works. And their ranges are much longer often than Wi-Fi because they operate by means of what's known as a mesh network.

With Wi-Fi, all connections go via the router. If your sandwich maker wants to talk to your door bell, it has to send a signal back to that box and then out again to the door bell. With a mesh, each device can pick up the wireless signal from any other device, so messages can be sent from point to point in a more direct manner. It also means that each location can work as a hotspot of sorts meaning that even gadgets in your loft can pick up a connection. The other bonus of a mesh network is that, if one device on it drops out, then there are other alternative routes that the signal can take and it won't wipe out the whole system.

Unlike Bluetooth, you can also load up ZigBee and Z-Wave with hundreds of smarthome devices. So, they have range, they have low power consumption, they have plenty of room for expansion and they are robust too.

What are the differences?

Z-Wave has a slighter better range at about 40m. The signal can perform four hops after the initial journey from the hub to the first product, so the maximum range gets up to around 200m making it suitable for a home even the size of Buckingham Palace. With ZigBee, each hop is only about 10m but the signal can hop many more times. As a result, it can support over 65,000 devices on a single network compared to 255 on Z-Wave. The only real limitation for ZigBee is making sure that no single smart device is any further than 10m away from any other.

The difference in range is down to the frequency upon which each standard operates. Z-Wave works at around 900MHz and ZigBee at 2.4GHz more often than not. That higher frequency with ZigBee can offer faster data transfer rates but the signal degrades more quickly. ZigBee does have the capability to work at around 900MHz but not everywhere. The other bonus of working at 900MHz is that it won't interfere with your mobile phone, your Wi-Fi or Bluetooth, all of which also kick about on the 2.4GHz part of the spectrum. So, there's an argument that Z-Wave could be a better choice.

All the same, Z-Wave is not out in front as the market leader, at the time of writing, in terms of numbers. It has 350 manufactures signed up with their 1500 devices which have clocked up a total sales of 40 million Z-Wave units worldwide, which is not bad. ZigBee has around 1,000 products from 425 companies and claims to be shipping around 10-15m each year which is very possible given that a lot of smart energy metres are ZigBee certified.

The only other point of consideration is that Z-Wave does come with the built-in guarantee that it will always be backwards compatible with older Z-Wave devices, no matter how much it's updated and changed over time. So, if your Wi-Fi hairdryer works on it today, it always will.

And then there's Thread…

Thread is the Google-owned new kid on the wireless smart home standard scene. Created by Nest Labs along with Samsung and ARM among others, it's already gathered a lot of device support by partnering with ZigBee. The two use the same base form of communication within their networks and operate on the 2.4GHz frequency, so it's a natural match.

Both are open standards, meaning that the technology is publicly available to all whom wish to use it, and that's not the case with Z-Wave. In fact, Nest Labs have recently announced the availability of an OpenThread reference code for developers to tinker with. The possible advantage to Thread is an eye on accelerating the smart home timeline with Thread tech at the helm.

Which standard is going to win out?

Each of ZigBee, Z-Wave and Thread are perfectly good enough to do the job even going into the future. They have their respective advantages. Some sort of Thread/ZigBee outcome seems a likely situation but not everyone is going to be keen on letting Google rule the smart home. Of course, there might not be much choice in the matter if more de facto gadgets like Nest arrive on the scene.

As it stands, Samsung's SmartThings ecosystem is happy on both ZigBee and Z-Wave. Philips Hue works on ZigBee and there's even ZigBee tech inside the Nest. ZigBee has a lot of expertise at the moment in smart energy systems and Z-Wave is good for security but these are by no means exclusive nor exhaustive skill sets.

Ultimately, a lot of the devices seem to find a way to work with whatever's going on around them and we've not yet met a piece of kit that wasn't happy to work in our smart homes.

Do you need to worry about this?

In a lot of ways, probably not. There is a lot of cross compatibility behind the scenes. Often it will be a case of a particular device coming either with multiple standard capabilities embedded or its own dedicated hub to work with. A lot of Wi-Fi routers come with the smart home standards inside them and even with something as potentially tricky as the Apple HomeKit platform, which is not intended to be compatible with any of the above, there are already plenty of behind the scenes bridges and chips that will make everything work together - and all without you having to know about it.

It's also worth noting the OpenHab standard which is an entirely open source wireless standard which has the aim of being entirely universal and platform neutral. With interest all around and such a wide array of options, it's unlikely that anyone or smart thing will be left in cold.

Going forward, we may find the odd problem case by case but it's more likely that the standards will be sorted out one way or another by the time any significant issues arises. It's in everyone's interest to make all of this work and the same manufacturers are signed up to multiple standards. What's more, with so many format wars over the years, it feels like the planning is being done well in advance this time. After all, the smart home still has a long way to go.



  • yogibimbi says:

    How secure is any of these systems against outside intrusion? I mean, if somebody got a hold of the remote and managed to convince my toaster, that it has to kill me, that would be pretty inconvenient.

  • LarryS says:

    "The other bonus of working at 900MHz is that it won't interfere with your mobile phone, your Wi-Fi or Bluetooth"

    Unfortunately, it runs head-on into older technology, such as cordless landline phones and baby monitors, to the point where 900MHz wide-area wireless internet service still encounters fatal interference levels in places where even long-distance 2.4GHz is viable.

    • stephan says:

      Only in very limited situations. As Wifi has become ubiquitous and landline phones are less essential you find much more interference in the 2.4GHz range. When I scan for Wifi in my apartment I find at least 11 publicly broadcasting SSIDs, besides probably some hidden ones and any Zigbee and Bluetooth devices nearby.

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