Bluetooth AoA Direction Finding Study Finds Limitations

While we wait for products based on Bluetooth 5.1 direction finding to reach the market, researchers in the UK and Italy have performed a study Dead on Arrival: An Empirical Study of The Bluetooth 5.1 Positioning System.

The paper tests the market readiness of the Bluetooth 5.1 direction finding by experimentally evaluating the performance of the AoA mechanism. The authors took Software-Defined Radios(SDR) manufactured by Ettus Research and emulated Bluetooth AoA data in order to assess the potential accuracy and security.

The results show that accurate angular detection is limited to a restricted range:

“Observe that the error is below 85 cm for more than 95% of the positions. However, this is far from meeting the centimetre level accuracy expected by IoT applications, since the absolute positioning error is <10 cm only in 15% of cases. Although offering sub-meter accuracy, is far from achieving centimetre-level precision.”

It was found that a malicious device can easily alter the truthfulness of the measured AoA data by tampering with the packet structure because the Bluetooth 5.1 standard doesn’t enforce any security provisions. The researchers suggest an improvement to the standard, by changing the receiver, so that instead of using one main antenna and switching to the other only for measuring the phase-delay, it keeps the other antenna active for the next packet to be received.

Nordic Wireless Quarter Magazine Available

Nordic, the manufacturer of the System on a Chip (SoC) in many beacons, has the latest issue of Wireless Quarter Magazine. It showcases the many uses of Nordic SoCs.

News from the world of beacons includes:

  • Quuppa partnership – this might accelerate Bluetooth direction finding solutions
  • Beacons helping visually impaired
  • Beacons for robot perception and interaction
  • Beacons in restaurants

Bluetooth AoA Direction Finding Antenna Design

We have previously mentioned that antenna design is a complex area that will slow the rollout of Bluetooth AoA direction finding solutions. What are the issues?

Theodoros Prokic of the KTH Royal Institute of Technology has a new paper on the Antenna Design for Angle of Arrival Measurement in Access Control Applications (pdf) that explores the antennas needed for two sides of an in an inside-outside scenario.

The paper provides an analysis of the challenges the antenna designer faces when creating an AoA solution. Issues include orientation and polarization, matching, coupling, reflections, phase center, and physical size. Designing and creating antennas can easily lead to inconsistent results due to the affects of hardware, cables and other testing equipment in the vicinity.

New Interview with Quuppa

Mister Beacon has a new interview with Fabio Belloni of Quuppa. It clarifies that while Quuppa uses direction finding techniques and contributed to the Bluetooth 5.1 direction finding standard, their solution is based on Bluetooth 4 and is a proprietary, not standards based solution. Their solution will continue to be provided alongside their new products based on Bluetooth 5.1.

The interview mentions how the Bluetooth 5.1 direction finding standard might need to evolve to provide less ‘chatty’, shorter communication in order to be suitable for all usecases, particularly those that are battery powered or need to have very large numbers of assets being tracked.

It’s also mentioned that the Bluetooth direction finding standard doesn’t cover tools needed to setup and control direction finding systems. It also doesn’t specify antenna design that’s a complex area.

As we have also experienced, there’s mention how some Ultra Wideband (UWB) vendors and ISVs are moving to Bluetooth for reduced costs, reduced power requirements and compatibility with other devices (tablets, phones and single board computers) that also use Bluetooth LE.

There’s also a recent article by Quuppa on Quuppa’s Role Regarding the New Bluetooth SIG Direction Finding Feature. It explains how AoD will require work by software operating system providers, hardware ODMs, silicon vendors and direction finding product providers before products appear in the market.

Location Beacons

We sometimes get asked for location beacons or which beacons are best for determining location. All beacons can be used for locating. While there are physical aspects such as battery size/life and waterproofing that make some beacons more suitable for some scenarios, locating capability is determined more by the software used rather than the beacons themselves.

Our article on Determining Location Using Bluetooth Beacons gives an overview on locating while the article on Using Beacons, iBeacons for Real-time Locating Systems (RTLS) explains how RTLS work. If you wish to create your own locating software we have a large number of posts on RSSI.

If you have been attracted to Bluetooth by recent announcements on Bluetooth direction finding, be aware that no ready-made hardware or software solutions exist yet. It will take a while, perhaps years, before silicon vendors support Bluetooth 5.1 direction finding, silicon vendors create SDKs and hardware manufacturers create hardware.

New Bluetooth Direction Finding Feature

A new direction finding feature has been released for Bluetooth 5.1 (pdf). Using more than one antenna, as used by Quuppa, allows for direction finding.

The paper on Enhancing Bluetooth Location Services with Direction Finding explains how location services currently use RSSI to estimate the distance. Direction finding introduces more advanced Angle of arrival (AoA) and angle of departure (AoD) techniques into Bluetooth 5.

“Should smartphone vendors choose to include Bluetooth direction finding with AoA support in their products, item finding solutions could be enhanced to provide directional information.”

As with the move from Bluetooth 4 to Bluetooth 5 it’s going to be while before we see (non Quuppa) products with direction finding. This feature requires specific hardware and software. Before that, it needs SDKs from the SoC vendors. Existing smartphones, beacons and gateways won’t be able to be upgraded.

Read about Using Beacons, iBeacons for Real-time Locating Systems (RTLS)