What is Thread?
Thread is a radio networking standard based on IP that was specifically developed for use in a smart home. Thread’s big selling points are speed and reliability. A motion sensor will turn your lights on in a millisecond compared to a second, and your network won’t go down because you accidentally unplugged the hub, as —with enough devices deployed— a Thread network can self-heal. Thread networks also automatically extend their range every time you add a device that can function as a Thread Router.
Unlike existing technologies that rely on dedicated bridges ("hubs") that create a single-point of failure, Thread network routing and bridging is built into the devices themselves, and each Thread device that you add as a router extends and adds redundancy to the Thread mesh network.
There are three types of Thread Devices:
Thread Border Router: a Thread Border Router connects Thread devices to IP networks. An example of this is the HomePod mini and AppleTV 4K. This then allows a Thread device to communicate with a non-Thread device via Matter/HomeKit. It also allows a Thread device to communicate with the Internet.
Thread Router: a Thread Router connects Thread devices to other Thread devices. They are what creates and extends the Thread mesh network. Since more power is required for a router, Thread Routers would typically be devices that are connected to power (like wired light switches, outlets, etc) and not battery-powered devices like sensors.
End Device: a Thread End Device connects to a Thread network but does not forward a signal or extend the network. They typically (but not always) need to conserve energy and run on battery power, like sensors.
What Makes Thread a Better Wireless Protocol?
Unlike Bluetooth or Wi-Fi, Thread was specifically developed as a smart home protocol. Other protocols used in the smart home to date have been co-opted into that role, meaning they have practical and usability issues. Wi-Fi is too power-hungry for battery-powered devices. Bluetooth has range limitations. Zigbee and Z-Wave require dedicated hubs, which are cumbersome to set up and maintain and can be a single point of failure.
Wi-Fi was never designed with home automation in mind, and it is a relatively complicated protocol to implement. It doesn't handle hundreds of connected devices very well (especially consumer networking access points and routers). It has high latency, which means that there is a longer delay between the time that you hit a button and a device responds. It is susceptible to interference. It requires lots of power, so doesn't lend itself to small, battery operated devices (like door locks, doorbells, and sensors).
Thread was designed from the start with home automation in mind. It is a simple protocol designed with low latency, requires very little power, and can automatically extend itself by creating its own mesh network. Thread was designed to work with hundreds of devices connected. It can also reroute the network traffic if a device is removed or unavailable. Think about why people love their Lutron light switches so much: they always work, they are reliable, and they are very responsive. This is because they are using their own proprietary radio network protocol that automatically creates an extendable mesh network with themselves. Thread is basically built like Lutron's radio protocol, but uses IP as a foundation.
Thread also has some advantages over bridges. With bridges and hubs, there’s a translation that happens; they see the data sent to them and then translate it from one environment to the other. A Thread router only ‘routes’ data. It doesn’t translate or even see the packages it’s transferring.
How does Thread Integrate with HomeKit?
While Thread is IP-based, it's important to note that a Thread network is a completely separate network from your home network, with a completely separate address space. If your home network's router goes down, the Thread network will continue to operate.
Thread integrates with HomeKit via a Thread Border router (see above). The HomePod minis and AppleTV 4Ks have Thread radios in them and can act as Thread border routers. These two Apple border routers allow Thread devices to integrate into a HomeKit network, and allow them to appear in the Home app, and respond to Siri commands and automations, and enable you to obtain data from and control your Thread devices remotely.
Designed for home automation from the start
IP based: can integrate with home Wi-Fi network
Low-latency: quickly executes commands
Low-power: suitable for small, battery operated devices like sensors
Designed to handle hundreds of devices
Easily extendable mesh network: each device that can act as a Thread Router extends the network and adds redundancy
Self-heals: if a device is removed or unavailable, the Thread network will reconfigure itself
No management: automatically configures itself
Thread's Website: https://www.threadgroup.org/