Channel Sounding - Speed and Multiple Devices

[MatthewP]

Hi,

We are evaluating BLE Channel Sounding for indoor localization of small mobile robots. We need 2D localization within the room, so we would need to measure the distance to multiple anchors.

We have some basic questions about this:

• How fast can a single distance measurement be performed? I've seen numbers in the range of 100ms?
• Is it possible to be paired with multiple anchors and perform BLE CS sequentially without having to establish a new connection each time?
• When can we expect an update of the SDK with CS support?

Thank you very much for your response.

BR, Matthew

[msip]

Are you testing between with two nRF54L15-DKs using nRFConnect SDK 2.8.0?

[MatthewP]

Sorry, my question wasn't clear in that regard and it seems I have missed the support for CS in the release notes for 2.8.0.

So at the moment we aren't testing with DKs at all yet. We wanted to know whether it was even worth trying it out, depending on potential limitations from my first two questions.

In essence we would like to know how fast the positioning can run (in PBR mode for higher accuracy) and whether we can perform the ranging quickly with multiple connected anchors.

[Simonr]

Hi

1. As we Channel sounding is still experimental on our end, I'm not sure we have the lowest possible time yet, but under 100ms seems doable at least. I assume you mean a ranging after the devices are connected and synchronized, correct?
2. I have asked the developers of the channel sounding features in the nRF Connect SDK about this, as I am not sure from just reading the spec and technical overview.
3. Experimental support was indeed added as of NCS 2.8.0. More details available here.

I'll let you know when I hear back from the devs regarding question 2, and if they have some more input on your first question.

Best regards,

Simon

[MatthewP]

Hi Simon,

1. Yes, exactly. The question is basically "under ideal conditions with all devices connected, which ranging update rate can I expect".
2. Great, thank you!

Thank you for your help, very much appreciated.

BR, Matthew

[Simonr]

Hi Matthew

I got a reply from the devs now, and I'm still waiting on a specific answer on question 1, but here are some preliminary responses.

1. This is very situational, but it's worth noting that CS can be started by setting the max_procedure_count=0, that means that CS procedures will continue to run on the ACL indefinitely or until explicitly disabled. In principle you could start a new CS procedure every ACL interval (minimum 7.5ms). 7.5ms is most likely not getting enough CS measurements in that time to do any accurate distance estimatio., but you can configure it so that a new procedure starts once you have collected enough CS measurements in the current CS procedure, to continuously get new measurements.

2. Having multiple peripherals connected at the same time to do sequential CS should be possible in the current NCS 2.8.0 implementation, although we haven't done any testing on this. Note that the central device would be using a lot of memory to store CS measurements from each peripheral device it is connected to and performing CS with. The ACL interval also needs to be noticably higher for the conncetions in order to not get scheduling conflicts between different links.

Best regards,

Simon