Bluetooth 5.1 Angle of Arrival backward compatibility

Question

I am currently designing a simple indoor location project to evaluate possibilities of Bluetooth 5.1 standard. The feature I would like to use is AoA (Angle of Arrival) introduced in Bluetooth 5.1.

According to the standard, AoA allows to measure position of a transmitting device (tx) by approximating the angle and measuring RSSI on a locator/receiver (rx). Since AoA is a feature newly implemented in 5.1, I understand that rx needs to support 5.1 Bluetooth standard. How about the transmitting device? What is the minimum version of Bluetooth it needs to support? Can I use 4.x BLE beacons (or Android/iOS devices simulating beacons) for this purpose?

Answer 1

The implementation uses an extended version of the advertisement data that contains a "Constant Tone Extension". Both devices need to support this feature in order to calculate the angle. So no you can not use old 4.x devices. Both devices must explicitly support this feature, and use it. Keep in mind that far from all Bluetooth 5.1 and 5.2 devices support this feature.