The smart home is not as simple as it should be. Nick Peers separates the ZigBees from the HomeKits to reveal what you need to know, and what's compatible with what here in the UK

Updated: Today’s connected home is not quite the nirvana we want it to be. Instead of smart devices working perfectly in unison, it’s like the Tower of Babel, with devices essentially chattering in different, competing languages. If you look on the side of your smart kit’s box, you’ll see a bewildering array of terms, from the likes of SmartThings and Nest to obscure references to Z-Wave and HomeKit. What do these terms mean, and how do they link together – assuming they can at all?

Building a smart home should be simple, but with no clear standards defined, it’s can be a tricky, messy and potentially very expensive business. This is where we’ve come in – cutting through the jargon and providing you with the means of understanding how your smart devices communicate, and what you need to do to bring them together.

SmartThings-Hub

If your smart devices require a hub, it’s because they’re not broadcasting over Wi-Fi.

What’s a protocol anyway?

The first hurdle you need to clear is that of how your devices physically communicate – and which set of rules (protocols) they use. In theory it should be as simple as connecting everything to your local Wi-Fi network, right? Not quite. Wi-Fi may be ubiquitous and convenient, but its power-hungry nature makes it unsuitable for use with low-powered devices such as motion detectors or smart smoke alarms that run off batteries for years at a time.

If Wi-Fi’s a no-no, how do these devices communicate with each other – and ultimately you? There’s a specific standard for low-power, low-speed networks, called 802.15.4, but unfortunately it’s not universally used in the same way. Instead there are actually four major protocols in existence. The first is Bluetooth, or more precisely Bluetooth LE or Bluetooth Smart. Then there’s ZigBee, Z-Wave and – coming up on the rails fast – Thread.

All four networks share similar characteristics:

1. They communicate in a similar manner

Because low power restricts the range of individual devices (as little as 10-20m in perfect conditions for ZigBee devices), each device also talks to another device, which extends the range as whole. If you drew a picture of it, the devices and connections would form a mesh, hence they are all described as ‘mesh networks’. The upshot is the more devices you have in the mesh, the better the network performs.

2. They share a similar underlying standard

They also share the 802.15.4 standard, because they all operate on different frequencies, there’s no direct communication between them. Thread and Bluetooth operate within the same frequency band as Wi-Fi, while Z-Wave uses a lower frequency to try and avoid interference with other networks. ZigBee however can transmit over both frequencies.

3. Yet they are all incompatible

As a result of the above, access to Bluetooth, ZigBee and Z-Wave requires specific and largely incompatible equipment – in the case of Bluetooth, most modern smart phones should be able to address devices directly, but with ZigBee and Z-Wave networks, you’ll need a smart hub to communicate with these low-power devices.

The hub not only communicates using the devices’ own network protocol, but also supports Wi-Fi to relay those signals to your smartphone or other controller. Some – like the latest SmartThings hubs – actually include radios for all five protocols we’ve mentioned. However, even if devices share the same protocol or can communicate between protocols, that doesn’t mean they can communicate. That boils down to which standards – or languages – they support.

  1. 1. What’s a protocol anyway?
  2. 2. Why all the competing standards?
  3. 3. Still confused? Our table will help
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