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BLE Standard Brings RTLS Functionality to Beacons

The Bluetooth Special Interest Group's new 5.1 standard comes with angle-of-arrival and angle-of-departure direction finding functionality, so that solutions can be built to locate the position of a tag or mobile phone within centimeters.
By Claire Swedberg
Mar 06, 2019

The Bluetooth Special Interest Group (SIG) has released a new direction-finding feature for location services as part of its specification update 5.1, making angle-of-departure (AoD) and angle-of-arrival (AoA) standard functions that Bluetooth Low Energy (BLE) beacon technology companies can build into their solutions. That means Bluetooth beacons can comprise a real-time location system (RTLS).

The technology can be used for asset tracking with AoA and wayfinding, or for other smartphone-based systems using AoD. These direction-finding features, built on top of BLE 4.0 and enhanced with proprietary extensions, are already being sold as parts of proprietary solutions, such as those from Quupaa.

The Bluetooth SIG's Ken Kolderup
With the direction-finding feature in the 5.1 specification, says Ken Kolderup, the Bluetooth SIG's marketing VP, "We're adding a new capability that is targeted to up our game in location services." The 5.1 feature will allow BLE companies to offer solutions by which a Bluetooth device can be trackable down to a location level of a few centimeters. Bluetooth beacons are already being used to identify where individuals or items are located, but not with the granularity afforded by direction-finding.

The AoD and AoA features consist of a beacon (also known as a locator) with multiple antennas rather than the standard single antenna, making it possible for a system to detect the angle at which a signal is sent and received. In the case of AoD, the technology could enable a smartphone to serve as a receiver to identify its own location, based on the angle of the signals transmitted by beacons operating within its vicinity. In another scenario, the phone could employ the antenna array built into it to take samples of beacon transmissions, and thereby understand the exact direction from which the transmission was received. A phone receiving these multiple signals could then utilize both triangulation and trilateration to narrow down the location.

With AoA systems, asset tracking is enabled using tags transmitting via Bluetooth, as well as nodes with a multiple-antenna array built in, serving as locators or receivers. Those receivers measure the angle of transmission from the asset tags and send data to a server.

Traditionally, Kolderup says, most Bluetooth beacon solutions rely on received signal strength indicators (RSSI) to estimate the distance between two devices and thereby calculate the general location of a tag or smartphone. Whether a solution offers wayfinding to help a mobile phone user identify where he or she is, or large-scale, complex asset- and people-tracking capabilities, the technology has based location data on signal strength measurements.

"That's been great," Kolderup says. "The basic approach has allowed the location services market to really take off well for Bluetooth." However, he adds, as technology evolves and as users become more accustomed to a variety of location services, "There has been a market demand for enhanced performance." While asset tracking now can employ Bluetooth beacons to identify location within about a meter-level accuracy, users are seeking something that can provide centimeter-based granularity.

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