As the new smart home standard Matter gets closer to launch, connected devices built on Thread — a technology that’s integral to Matter — are starting to roll out. In the last year, Eve, Nanoleaf, Schlage, and Wemo have released smart home gadgets such as motion sensors, light bulbs, door locks, smart plugs, and motorized blinds that run on Thread. But just what is Thread, and why does it matter to Matter?

I sat down with three Thread Group board members to find out how this “new” protocol (it’s actually been around since 2015) promises to fix many of the smart home’s biggest issues: reliability, speed, connectivity, and scale. I spoke with Vividh Siddha, president of the Thread Group and director of software engineering at Apple, Jonathan Hui, vice president of technology for Thread and principal software engineer at Google, and Sujata Neidig, vice president of marketing for Thread and director of marketing at NXP.

As you may have spotted in those bios, Thread — like Matter — is being developed by a consortium of competing companies in the smart home industry. Only Thread started much earlier than Matter. “In 2015, several companies got together and identified a problem in the industry and that we can work together to bring a solution to the market,” says Neidig.

That problem was how to securely and simply connect all the various devices in the consumer smart home. The solution they came up with was Thread, an IPv6-based wireless protocol that could create “a secure, robust, reliable, and simple-to-use network.” Today, Thread is run by a board of directors that includes representatives from Google, Apple, Amazon, Samsung SmartThings, Qualcomm, NXP, Assa Abloy (owners of Yale and August), Lutron, and more.

---

What is Thread, and why is it important to Matter and the smart home?

Thread is a wireless protocol specifically built for IoT devices. It’s designed to make them work faster, have fewer points of failure, use less power, and communicate with each other more seamlessly.

A low-power, low-bandwidth mesh networking protocol that uses the 802.15.4 radio technology, Thread is similar to existing smart home protocols Zigbee and Z-Wave. But unlike them, it doesn’t need a central hub or bridge. Instead, Thread devices can talk directly to each other. By cutting out the middle man, Thread can be faster, especially over large networks.

Also, unlike the other low-powered smart home protocols, Thread is internet protocol (IP)-based, meaning it can directly connect to any other IP-based device, such as smartphones, tablets, computers, and Wi-Fi routers. “What makes it unique is that it was built on IP,” says Neidig. “We are bringing the same protocol that the internet runs on to run on small devices.”

Matter is an application layer that runs on Thread. “Matter supports both Wi-Fi and Thread for connecting devices, and Thread provides that reliable mesh capability so there is no single point of failure,” explains Neidig.

When Matter arrives later this year, Thread will be the protocol it uses for low-bandwidth devices, such as door locks and motion sensors, and Wi-Fi and Ethernet will be used for high-bandwidth needs, such as streaming video from a security camera. Finally, Bluetooth LE will be used for onboarding devices to a Matter network.

Why is Thread a better smart home protocol than those we already have?

“Thread was designed from the ground up to be an IoT low-power protocol that supports low latency. That’s its purpose,” says Hui. “A lot of the other technologies [used in the smart home] were designed to optimize other applications. For example, Bluetooth was originally designed as a wire replacement. Thread was designed for devices that just want to sleep for a long time, wake up, send a single packet, and then go back to sleep and preserve battery for as long as possible.”

Thread’s direct communication capability, combined with its ability to handle scale (over 250 devices), means lower latency. Benchmarking tests run by Silicon Labs show Thread thrashing Zigbee and Bluetooth in latency tests, especially in large networks with many devices.

“Also, a Thread mesh [can work] as a routed mesh, which means the devices are proactively looking for the best route to every other device in the network,” says Hui. This efficiency translates directly into reduced power consumption as well as reduced latency. As a mesh network, Thread is self-healing; if a router (see sidebar) drops offline, another one can pick up the slack so your network doesn’t go down.

Image: Thread Group

Does Thread really replace the need for any kind of hub or bridge?

“Yes, although it does require a border router to bridge the Thread network to the internet. But it avoids you having a different bridge for [multiple] devices,” says Siddha. Instead, any Thread device can connect to any Thread border router — regardless of manufacturer. Additionally, unlike a bridge or hub, a Thread border router can’t see the traffic it routes, as all communications in a Thread network are encrypted.

A Thread border router is not a dedicated device like a bridge or a hub. “A border router is a feature that can be integrated into any device that’s powered all the time, like Nanoleaf light panels, the Apple TV, or [a] HomePod Mini,” says Neidig.

Do you have to have a border router to use a Thread device?

“No, you don’t need a border router for Thread devices to talk to each other. But you need a border router if you want them to talk to other networks in the home or the internet,” says Hui.

Photo by Jennifer Pattison Tuohy

Will Thread work when the internet is down?

“Yes, Thread devices will. A Thread network will not go down if the internet goes down because it’s not doing anything in the cloud,” says Hui. “The network is self-configuring, self-healing, self-managing even. And it’s all done locally.”

Which specific products benefit from Thread? It’s not designed for every product in the smart home, is it?

“No, it’s not. And looking at the current [smart home] use cases, the biggest elephant in the room in terms of bandwidth are cameras,” says Siddha. “Thread can be used for all sensors but not for high bandwidth use cases like cameras. Cameras are among the few IoT devices that require high bandwidth. Every other use case for a sensor or IoT accessory can be satisfied by Thread.”

Thread is specifically designed for small, low-powered devices — leak detectors, CO detectors, and motion sensors. These may be left untouched and unused for months or more but need to reliably spring into action when required and crucially need to not have run out of battery. “In addition to sensors, it’s designed for actuators as well — things like door locks, window shades, light bulbs, wall plugs, water valves, thermostats, thermostatic radiator valves, alarm sirens, etc.,” says Siddha.

Why are there so many versions of Thread? There’s Matter over Thread, HomeKit over Thread, Google / Weave over Thread, Open Thread, and so on.

“Those are all the same Thread; they’re just different application layers running over Thread,” says Hui. “That’s actually one of the key highlights of the importance of IP [in Thread]. It’s the same network technology; it can support multiple different application layers simultaneously. Matter over Thread is just another example of an application layer over Thread.”

The latest release of Thread 1.3.0 addresses a significant problem around these different versions, allowing them to interact with each other. “Previously, different ecosystems didn’t have a good way for sharing this Thread network credentials with each other,” says Hui. “That’s changing.”

Combined with APIs announced by Apple and Google for sharing Thread credentials between different mobile apps, the latest release of Thread — Thread 1.3.0 — will allow users to have one unified Thread network in their homes.

With 1.3.0, if a home network has an Apple HomePod Mini, a Google Nest Hub, and an Eero Wi-Fi router, they can all act as border routers in a single Thread network. That’s not how it is today, and likely, we won’t see all devices update to Thread 1.3.0 until closer to when Matter arrives this fall, says Hui.

The origins of Thread go back to 2011 and the first Nest Thermostat. Why has it taken so long for it to be adopted in the smart home? And why are there so few Thread products available?

“Thread had an inflection point probably two or three years ago when both Google and Apple came up with border routers,” says Siddha. “Then we were able to finally see Thread devices in action. Turning on a [smart] light switch was literally as good as turning on a physical light switch. That was not the experience people had before.”

With border routers beginning to enter the wild, companies like Eve and Wemo, who had previously used Wi-Fi or Bluetooth, started to look at shifting. “They saw the issues with [the other protocols] and now, seeing the maturity of Thread, are adopting Thread into their products and making a conscious switch from a different technology to Thread, for the benefits of the reliable, secure, instant control experiences,” says Neidig.

However, there are still very few Thread devices available (see sidebar), and some that are — such as the Nanoleaf Essentials A19 bulbs — won’t be compatible with Matter when the standard arrives. Similarly, a number of Google products with Thread — such as the Nest x Yale door lock — are based on earlier implementations of Thread and don’t support the features required for Matter.

Amazon has announced its Echo smart speaker (fourth gen) will be updated to become a Thread border router.

What about backward compatibility? If Thread was built on Zigbee, can’t all Zigbee devices be upgraded to Thread?

“Technically, Zigbee runs on 802.15.4 radio just like Thread. So, current Zigbee products could be upgradeable to Thread,” says Neidig. “But because it’s IP-based, Thread has different resource requirements — like memory. If a product isn’t built with the right resource structure, it won’t be upgradeable.”

Image: Philips Hue

Can products that use hubs or bridges today, such as Philips Hue light bulbs, be upgraded to Thread through the hub or bridge? Or would you have to upgrade the individual bulbs?

“One constraint is: do the accessories — not the hub — have sufficient memory to support Matter over Thread,” says Siddha. If the accessories don’t, then the product can’t be upgraded to Thread via the hub (but it could work with Matter over Wi-Fi). “Those are considerations that product manufacturers will have to make,” he says. “As a general principle, if something is not broken, people don’t want to fix it.”

Philips Hue already works with almost every ecosystem, and the company has said it will support Matter through its existing bridge but that it doesn’t plan to replace its existing Zigbee-powered bulbs with Thread bulbs.

“In the longer term, I think products will undergo a natural evolution to [Thread],” says Siddha. But he hopes every company will look at bringing Thread into their existing devices, “Because it just gets us to this IP backbone [for the smart home] quicker.”

How will Thread and Matter work with Apple HomeKit?

“HomeKit will be this application that works on the Apple ecosystem. But uses Matter underneath,” says Siddha. “So, you will have HomeKit on our products, supporting Matter and Thread accessories. Then we have our own kind of user experience for HomeKit, just as Google will have their own. We expect the innovation to happen at that higher layer.”

Photo by Dan Seifert / The Verge

How will Matter and Thread ultimately benefit the smart home?

“For years, companies in the consumer smart home were trying to differentiate based on the connectivity they have [which platforms the device worked with],” says Hui. “That’s not what consumers care about. They care about the cool, fun features. Standardizing all these connectivity technologies gets the hard stuff around reliability and power out of the way. It lets the product companies focus on the new and exciting features consumers really care about.”

“The smart home today is like the early days of the internet,” says Siddha. “There are legacy technologies that weren’t coming together to make everything just work. Instead, there are all these multiple bridges and other devices you need. Thread, with its all IP-backbone, allows seamless access to the home network, essentially making home automation complete.”

Ultimately, Thread and Matter are a reset for the smart home. They are an attempt to rebuild a broken system and make it capable of fulfilling its initial promise; the intelligent technological evolution of our homes. Now they just have to actually arrive.