Bluetooth Direction Finding: Angle of Arrival (AoA) and Angle of Departure (AoD)

The Bluetooth 5.1 specification enhances location services with a direction finding feature that makes it possible to detect the direction of a Bluetooth signal. With Bluetooth direction finding, developers can bring products to market that understand device direction and achieve sub-meter location accuracy.

Applications for Bluetooth Direction Finding


Proximity marketing

Item Finding

Personal property tags

Real-Time Locating (RTLS)

Asset tracking

Indoor Positioning


Angle of Arrival (AoA)

  • Assets broadcast (TX) their location to an AoA locator such as a wireless access point (AP), connected light or smart luminaire
  • Locators measure the signal’s arrival angle

Angle of Departure (AoD)

  • Beacons transmit AoD information such as coordinates using multiple antennas
  • Mobile devices, including smartphones receive the beacons and calculates position

Bluetooth Angle Estimation for Real-Time Locationing Whitepaper

Bluetooth Angle Estimation for Real- Time Locationing

AoA Design Considerations

  • Assets only need a single antenna, can be low power, and simultaneously support additional Bluetooth LE functionality
  • Locators require 3 x 3 or 4 x 4 antenna arrays and switches
  • Edge gateways process angle readings and communicate to an asset management system in the cloud to determine device location

AoD Design Considerations

  • Beacons require 3 x 3 or 4 x 4 antenna arrays and switches
  • Mobile devices like smartphones need to support AoD algorithms
  • Beacon coordinates must be known by the location services system

Silicon Labs Direction Finding Solution

  • Bluetooth 5.1 stack with Direction Finding
  • Wireless Gecko EFR32BG13 Bluetooth SoC and BGM13 modules
  • Antenna reference designs and radio boards
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