Location Indoors: Bluetooth 5.1 Advances Accuracy

OK, so you’re in a giant mall, you want to find a store that sells gloves and you want to know how to get there. Or you’re in a supermarket and you need some obscure item, say capers, that doesn’t really fall under any of the main headings they post over the aisles. If you’re like most of us, certainly like me, this can be a frustrating experience. Modern stores know how to provide up-to-the-minute information, they provide wireless internet, usually, and we have our phones. But there’s been no way to provide the kind of service we take for granted with GPS – where is the thing I’m looking for and how to I get there? So we have to ask, or check mall maps, try to find the right store, try to figure out where we are on the map and try to figure out how we are oriented relative to the map. What is this, the Dark Ages?

The problem for indoor positioning is that GPS is quite literally dark indoors; GPS devices can’t see satellites in those cases. That’s pretty limiting, not just to personal convenience but also to enhanced automation. In industry 4.0 we want to track assembly progress through a production line, or locate machines having problems – all indoors. In a hospital, nurses want to find a crash cart when a patient goes into cardiac arrest – also indoors. You can’t afford to waste time finding out where a cart was last left. Less dramatically (Paddy McWilliams, Engg Dir at CEVA gave me this one), where the *#!@ did I leave my left earbud (maybe down the side of the sofa)?

Helping find something in these cases is an example of indoor positioning services (IPS). Tracking something which will frequently move (such as the crash cart) is classified as real-time location services (RTLS) and Bluetooth beaconing is a major player in both spaces. When you consider the size of the GPS market and the scope for similar services indoors, it’s not surprising that the Bluetooth beacon market has been estimated at $58B by 2025.

A challenge for Bluetooth in this kind of application has been accuracy since location has been determined primarily by signal strength. This gives an indicator of distance but not direction, and triangulation to multiple sources doesn’t help much, given limited range and need to consider noise and multi-path effects. Wi-Fi with triangulation suffers from similar problems, also unpredictable latencies. Another technology, ultra-wideband (UWB), claims accuracy to centimeter levels but is expensive in cost and power and interference is a concern near critical equipment. Frankly most of the time, we don’t need that kind of location accuracy. Get me in the ballpark and I can find it from there.

Bluetooth is a strong contender for IPS and RTLS for multiple reasons. It’s already in every mobile phone and virtually every other kind of mobile device. It’s best in low power (especially in BLE) and low cost. This already makes it good bet for mass deployment. If only we could fix that accuracy problem. That’s what the Bluetooth SIG has delivered with the 5.1 release of the standard, adding angle-of-arrival (AoA) and angle-of-departure (AoD) detection. These add directional information to the distance estimate derived from signal strength, allowing location of a device to be calculated with much higher accuracy, to within tens of centimeters to a meter in everyday conditions. That’s good enough for me to find where the capers are.

Two methods for angle detection let a product developer choose the optimum IPS approach to be used for the target application; AoA is aimed at very low cost tracking tags with location calculations performed by the infrastructure system, whereas AoD allows the location calculations to be performed at the mobile device, allowing greater privacy for the user.

Bluetooth 5.1 IPS accuracy is a perfect match in smart manufacturing, healthcare, proximity services in retail, way-finding in airports, shopping malls, and hotels, for all of which, sub-meter accuracy should be just fine. And using an already widely-established standard seems like an obvious advantage in scaling to these levels of deployment.

For RTLS, adding angular to distance-based estimation can improve tracking of rapidly-moving objects so it becomes easier to track assets moving around a factory floor. RFID is the classic solution here but is obviously very short-range, where Bluetooth 5.1 can reach several 100m indoors, making (semi-)continuous monitoring much more practical.

Bluetooth 5.1 comes with some cost. The transmitter and/or receiver need an array of antennae to support angle-detection, depending on whether you want to support AoD or AoA methods. But this is modest compared to UWB and provides an opportunity for solution providers to add further differentiation to their products.

CEVA provides Bluetooth 5.1 compliant IP, for both BLE and Bluetooth Dual-Mode, under the RivieraWaves family, adding to its existing support for location services in GNSS and Wi-Fi-based location. Check them out next time you circle the supermarket three times trying to find those capers.