Apple and Google recently unveiled a hugely innovative — and highly controversial — touch tracing program intended to help people stop spreading the novel Coronavirus by finding out who has had touch with infected patients.
While device specifics are still scarce — considering how early the project is in progress, not even Apple and Google have worked out anything out here yet — we do know a few things, including that the companies intend to use Bluetooth Low Energy (Bluetooth LE) radio technology as the heart of the network.
As the name suggests, Bluetooth LE is a low-powered alternative to standard Bluetooth technology, relying on shorter communication bursts which use less power than a typical Bluetooth link that is continuously transmitting. A perfect example of the distinction is how Apple’s Airpods work: A short-burst Bluetooth LE interface is used to trigger the initial interface and headphone pairing before transitioning to standard Bluetooth to download the music you want to listen to.
The choice of touch tracing device for Bluetooth LE is important for a few reasons. There’s a lot about Bluetooth LE on the surface which makes it perfect for this kind of use: About every single new smartphone on the market, from the lowest Android handset budget to the most costly iPhone or Samsung flagship, embraces this. And it’s a very robust design, one that operates with very low levels of power so as not to impact battery life.
One of the keys here is the proximity profile (PXP) of Bluetooth LE, the central technology on which Bluetooth depends on the positioning and monitoring of devices. By calculating how much power a Bluetooth radio signals absorbs (the RSSI value), we can measure how far it is from that. It’s how Airpods knows how to turn up the “Would you like to talk” dialog on your nearest phone and not the phone across the room from your friend, or how Tile trackers will help you find the lost keys.
Similar Bluetooth LE technology implementations have also been found in this field, with products such as iBeacons, hardware transmitters that can detect nearby users and activate location-based alerts when you’re nearby. Although iBeacons are usually used in retail stores to monitor consumers, deliver discounts, and display ads, baseline technology is currently somewhat close to the device introduced by Apple and Google.
However, it also highlights the flaws: to go back to our analogy with Tiles, anybody who has used one of the trackers knows they’re only useful for a certain degree of accuracy. Bluetooth can help you locate the rough region of your lost piece, but it’s not something Bluetooth LE tech excels in discerning the precise physical location. Interference can be a major concern too. The further barriers and obstructions between devices — such as backpacks, bags, doors, or windows — the poorer Bluetooth LE tracks something reliably, as such obstructions weaken the radio signal intensity used to determine distance.
And — at least on paper — Bluetooth provides a better alternative than QR codes already used in countries like South Korea because Bluetooth operates at a broader range than the optical scanners needed by QR or barcode technologies. Given that distancing remains a vital part of stopping the virus from spreading, a bonus is technology that doesn’t allow consumers to get close to patients (or their phones).