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.

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Achieving Sub-Meter Location Accuracy with Bluetooth Direction Finding

Applications for Bluetooth 5.1 Direction Finding

Point-of-Interest

Proximity marketing

Item Finding

Personal property tags

Real-Time Locating (RTLS)

Bluetooth Real-Time Locationing - Silicon Labs

Asset tracking

Indoor Positioning

Wayfinding

Silicon Labs Bluetooth Direction Finding Solution

Bluetooth 5.1 stack with Direction Finding
Wireless Gecko EFR32BG22 SoCs
Wireless Gecko EFR32BG22 modules
EFR32BG13 Bluetooth SoCs
BGM13 modules
Antenna reference designs and radio boards

Understanding Angle of Arrival and Angle of Departure

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

Angle of Arrival 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

Angle of Departure 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