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

Rightsizing Sensor Network Design for the IoT Whitepaper

Learn how to simplify your sensor network to measure only what can be translated into cost savings and a positive end-user experience

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