Bluetooth 5.1 Refines Location Accuracy

GPS direction assistance to get from A to B has become so commonplace that physical maps for most of us seem as antiquated as cassette tapes. Still, this class of technology only works outdoors because it needs a line of sight to satellites (and perhaps an assist from a cell base-station); none of this will work indoors. Should we care? Consider these cases: you’re in a subway station and you want to get to another line somewhere else in that very large station, or you’ve already walked around a supermarket/store three times and still can’t find the product you want.



Helping you with these use-cases is an example of indoor positioning services (IPS), a method to get you to a point of interest in a store for example. Alternatively, maybe you want to find a medical crash cart in a hospital – generally urgently. Or maybe you want to track assembly progress along a production line. These cases, tracking something which will frequently move, also depend on indoor location tracking and are classified as real-time location services (RTLS).


This is a market with very significant potential in which Bluetooth-based beaconing can be an attractive solution given its ubiquity and lack of need for additional infrastructure. One survey estimates the Bluetooth beacon market could be worth $58B by 2025, for a CAGR of 95%. However, until recently the accuracy of Bluetooth in this kind of application has been problematic because 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, given limited range and need to consider noise and multi-path effects.


In fact, a different technology, ultra-wideband (UWB) has been promoted as overcoming these problems with claimed accuracy down to centimeter levels. However UWB comes with its own challenges, notably an expensive radio chip, along with concerns that the signal could be disruptive to critical equipment such as in medical applications.


As a general-purpose wireless technology, and leveraging its ubiquitous adoption in mobiles, Bluetooth leads in cost, low power (especially in BLE) and ease of deployment, therefore making it work better for IPS and RTLS looks like a good bet for mass deployment. That’s what the Bluetooth SIG has aimed for with the 5.1 release of the standard, with the addition of angle-of-arrival (AoA) and angle-of-departure (AoD) detection. The resulting directional information coupled with a distance estimate derived from signal strength allows the location of a device to be calculated with much higher accuracy, to within centimeters in ideal conditions or to within tens of centimeters to a meter in everyday conditions.


By providing two methods for angle detection, Bluetooth 5.1 enables a product developer to 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 mobile user.


In many consumer, business and industrial applications, 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 most of these cases there is no need for centimeter-level accuracy. And the value of working with a widely established standard seems like an obvious advantage in scaling to mass deployment.


Importantly, 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 for asset tracking but is very short-range, where Bluetooth 5.1 can reach several 100m indoors. Checking moving assets from some distance using a BT5.1 radio can provide continuous location information versus the intermittent checks you would be limited to through hand-held readers.


Integrating with Bluetooth 5.1 isn’t free. The transmitter and/or receiver must host an array of antennae to support angle-detection, depending on whether you want to support AoD or AoA methods. But this is a modest incremental cost compared to the UWB option and offers an opportunity for solution providers to add further differentiation to their products.


CEVA now offers Bluetooth 5.1 compliant IP, for both BLE and Bluetooth Dual-Mode, under the RivieraWaves family, adding to our existing support for location services in GNSS and Wi-Fi-based location. You can learn more about our full range of connectivity and location technologies here.