Here’s why Apple put a Thread radio in the iPhone 15 Pro

Following Apple’s iPhone 15 announcement and the news that the iPhone 15 Pro and Pro Max will come with a Thread radio, I did some more digging into how Apple might deploy this wireless connectivity protocol in its ecosystem.

The smart home is the obvious answer and the one Apple halfheartedly offered (Thread is a main protocol for Matter). But adding the low-power, low-bandwidth, mesh-based Thread protocol could also signal the company is moving away from relying solely on Bluetooth for connecting to peripherals like the Apple Watch. Here’s a look at some of the ways that new wireless connectivity could be put to use.

The obvious use for Thread in the iPhone is as a Thread border router for the slew of new Apple Home and Matter-enabled Thread smart home devices from companies like Eve, Nanoleaf, and Belkin WeMo. This would mean you wouldn’t have to have a HomePod Mini, Apple TV 4K, or other Thread border router to use Thread smart home gadgets with your iPhone.

Jonathan Hui, VP of technology at the Thread Group and a software engineer at Google, confirmed to me that a smartphone can technically act as a Thread border router — even when running on battery power. (The Thread Group specifies that border routers should always be powered). “Like any Thread device, a smartphone can serve as a Thread end device, Thread extender, and/or Thread border router or a Thread provisioning device,” he said.

But using your iPhone as your one and only Thread border router would not be a good idea. A Thread border router is required to connect Thread devices, such as smart sensors, locks, shades, and lights, to the internet and to other IP-based smart home networks. If you used your phone to do this, your Thread devices would run into issues when you leave home or when your phone runs out of battery. This is similar to what happens if you connect devices to Apple Home over Bluetooth using your phone but don’t have an Apple Home hub.

So, while the iPhone could act as an additional border router (a Thread network can have more than one, which — in theory — helps with reliability for the mesh network), for most use cases, you would still need another Thread border router operating in your home.

Hui also says that Thread connectivity in a smartphone will allow it to communicate directly with a Thread device. “Compared to existing smartphones without Thread, a smartphone with Thread can communicate directly with a Thread device, without relying on a separate Thread border router or any other communication technology,” he said.

Again, this is similar to how devices connected to Apple Home work over Bluetooth today. But Thread has the advantage of being a self-healing mesh network with less latency at scale than Bluetooth. The most likely benefit in the short term will be speed. Even if you have other Apple Thread border routers, with Thread on your iPhone you’ll be able to control Thread devices like lights and locks directly without needing to go through a border router first.

As a local protocol with no cloud dependence, Thread is already very fast, so this probably won’t make a significant difference — unless you live in a really big house. Thread is designed to use less power, though, so there may be some longer-term benefit there.

Another possibility with direct control is some type of trigger or presence detection. Your Thread devices could know you’re home as soon as you walk into the house and respond appropriately. However, presence detection — something the smart home sorely needs — would be easier to do with the UWB chips already in most iPhones and HomePods (and is already being done to some extent).

“Thread has some interesting applications for outside of the smart home, as we see movement towards Thread in mobile,” says Daniel Moneta, a marketing and product consultant for Samsung SmartThings and former product marketing manager for Google. “In particular, the potential to be an alternative to Bluetooth for connecting peripherals to smartphones, such as smart watches, medical and fitness devices, and camera accessories.”

As an IP-based mesh protocol, Thread could be a more reliable way to connect multiple such devices to your phone while also having multiple “parent” devices within the same home (such as your iPad, MacBook, or other family member’s iPhones). Its IP characteristic makes it easier to maintain a persistent data connection directly to the device, says Moneta. Additionally, Thread being mesh means your device doesn’t have to be in range of the controller (iPhone/iPad etc.), as it would with Bluetooth.

This could apply to Apple accessories such as the Apple Watch and third-party devices that use Bluetooth, like camera accessories and medical devices. Of course, all of those would need a Thread radio in, too, so that’s not going to happen anytime soon. Plus, Thread is only on two iPhones in the line right now, so any Thread-based Made for iPhone accessories would have limited appeal until the chip rolls out down the line.

There’s also the matter of throughput. According to Google Home’s developer resources, Thread devices have a practical throughput limit of around 125Kbps, whereas Bluetooth LE 5.0’s practical throughput can be up to 10 times that.

Thread would be fine for most smartwatch uses but not for audio streaming (so probably not AirPods). And there’s nothing to say future peripherals couldn’t have both Thread and Bluetooth (as the iPhone 15 Pro does) and use whichever is fit for purpose. After all, many smartwatches have Wi-Fi radios that they’ll use if they’re out of reach of their paired phones.

A popular theory in my X (formerly Twitter) feed after the Apple event was that Thread is in the iPhone 15 Pro line more or less as a freebie. It’s plausible that the Wi-Fi / Bluetooth chip Apple is using in its highest-end phones comes as a sort of three-for-one: you pay for Wi-Fi and Bluetooth, and you get your Thread for free!

Case in point: this tri-radio chip that NXP announced at CES 2022. If that’s indeed the case, it’s likely we’ll see Thread trickle down through the iPhone line slowly, probably showing up next year on the base-model iPhone 16 — right around the time Matter might actually be working. I reached out to Apple for comment on this but did not hear back.

Given that Apple itself doesn’t seem to have a clear idea or any concrete examples of what the Thread capabilities will add (beyond a vague “opening up future opportunities for Home app integrations” statement in the iPhone 15 press release), this does seem to be the most likely reason — for now. Although, Apple rarely does anything without some purpose in mind.

At the very least, the addition of Thread makes the iPhone 15 Pro the most smart home-friendly option if you’re in the market for a new phone. At least until Google’s Pixel event next month. (Remember: Thread essentially began with Nest, and most Google Nest products use Thread.)

The Thread radio in the iPhone adds some intriguing futureproofing, and as a smart home user who bought an iPhone 14 last year and was not planning on upgrading anytime soon — my plans may be changing.