I just read

Bluetooth Direction Finding, added to the Bluetooth spec as part of Bluetooth 5.1 to allow devices to measure angle of arrival and angle of departure (AoA and AoD) to position devices to an accuracy of under one metre (around 3.3 feet.)

(read it here).

I am excited about the idea, but want to be sure that I have understood it.

If I want to track people/objects and report their locations to a server, I imagine that I need a BLE Gateway/router.

I assume that the devices would send advertising packets, the gateway would receive these, detect the device location and send it via HTTP(S) to the server.

I also assume that only the BLE gateway/router needs to be BLE 5.1, since it is the one performing direction finding.

Are my assumption correct? Does it work that way? Can a BLE 5.1 gateway perform direction finding on a BLE 4.0 advertisement?

I welcome any more info, such as tutorials, videos, books, etc

  • 1
    You’ll find a detailed explanation of how it all works here: bluetooth.com/wp-content/uploads/Files/developer/… As far as I understand it, no, you need both ends to have BT 5.1 support (though in different ways, and it depends on whether you are using AoA or AoD), at the very least at the software/firmware level. – jcaron Oct 28 '19 at 19:57
  • Thanks (+1). Feel free to post that as an answer (especially if you can summarize it, in case the link breaks) – Mawg says reinstate Monica Oct 28 '19 at 20:24

The way Bluetooth direction finding works is described in this document.

There are two scenarios:

  • AoD (Angle of Departure):

    • Sending device sends a "direction finding signal"
    • Sending device is equipped with a "phased array antenna"
    • Receiving device performs "IQ Sampling"
  • AoA (Angle of Arrival):

    • Sending device sends a "direction finding signal"
    • Receiving device is equipped with a "phased array antenna"
    • Receiving device performs "IQ Sampling"

As you see, in both scenarios, there are requirements on both ends. Some are definitely hardware upgrades (the phased array antenna). The rest (IQ sampling and sending the direction finding signal) may be possible with just firmware / software upgrades, depending on the exact implementation, though I kind of doubt it (it would also most likely require at least a change in the BLE chip firmware, not just a high-level OS/app change).

So, as far as I understand it at this point, you need BT 5.1 equipment at both ends to make it work.

I'd love to hear otherwise!

  • Thank you for an excellent and most helpful answer ! I look forward to your future contributions to the site. Now to buy some BLE 5.1 devices; hopefully ESP32, but STM32 will do – Mawg says reinstate Monica Oct 30 '19 at 7:25
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    I don’t think the ESP32 supports BT 5.1, does it? There’s an nRF52 IC with BT 5.1 (52811 IIRC), though I haven’t looked at the details yet and what it implies in terms of antennas etc. – jcaron Oct 31 '19 at 9:19
  • Well, I will go with that, then, until a suitable ESP32 comes along/. Thanks for the tip. I was hoping for something with both BLE5.1 and WiFi, to use it as a Gateway & Router, but can cobble something together for the time being – Mawg says reinstate Monica Oct 31 '19 at 11:37

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