Channel Sounding with Two Antennas: Data Dropouts after Adding Second Path (2 antenna)

RE: Channel Sounding with Two Antennas: Data Dropouts after Adding Second Path (2 antenna)

Amanda Hsieh — Wed, 06 Aug 2025 16:20:54 GMT

There is a ring buffer in the ranging service that contains step data. If it gets new data locally, it overwrites the old and can produce this log message. This is all open source in the SDK, and if you want to look more closely at what's going on, you can simply enable debug logs.

It seems you are clearly not using the samples out of the box since you've made all the modifications. So I recommend you start by trying the things I suggested above.

RE: Channel Sounding with Two Antennas: Data Dropouts after Adding Second Path (2 antenna)

witc — Wed, 06 Aug 2025 08:57:14 GMT

Hi Amanda,

Thank you.

[quote userid="77782" url="~/f/nordic-q-a/123409/channel-sounding-with-two-antennas-data-dropouts-after-adding-second-path-2-antenna/544468"]Is it possible to test with the nRF54L15DK?[/quote]

If I know there is only 1 antenna, but for comparison it would be OK.

[quote userid="77782" url="~/f/nordic-q-a/123409/channel-sounding-with-two-antennas-data-dropouts-after-adding-second-path-2-antenna/544468"] If there isn't enough time to transfer the data before more data is produced, the new data will overwrite the old.[/quote]

What do you mean? Isn't it more likely that due to e.g. bad RF conditions (interference, high latency, poorly designed HW..), it is not possible to read the step data from the reflector? Or I don't understand what you mean by short time - because my code is practically the same as your example ras_initiator - it doesn't do anything extra, so the CPU can't be extra busy because of me.

...but it is quite possible that the problem is with the custom HW, and the RF conditions are not completely ensured correctly

Thanks for now, I'll keep testing.

RE: Channel Sounding with Two Antennas: Data Dropouts after Adding Second Path (2 antenna)

Amanda Hsieh — Mon, 04 Aug 2025 13:13:16 GMT

Hi,

Can you share the rest of your parameters? Adding multiple antenna paths to channel sounding means the controller produces more data, which in turn means the devices need to exchange more data over GATT to produce distance estimates. If there isn't enough time to transfer the data before more data is produced, the new data will overwrite the old.

Here are two things to try:

increasing the procedure interval
increasing CONFIG_BT_RAS_RRSP_RD_BUFFERS_PER_CONN

[quote user=""]but not sure how it works - could not find the source code where the RF switch is swithed, is that correct?[/quote]

We've decided to make this part of the controller open-source, here: https://github.com/nrfconnect/sdk-nrf/blob/95a5a55be764e2dc756a43ce7b485ac3a978d65e/subsys/bluetooth/controller/cs_antenna_switch.c#L4, but it looks like you're already using it correctly, so no need to look at the code.

[quote user="witc"]My hardware is a custom board and HOLYIOT-24005 with nRF54L15 – both behave almost the same.[/quote]

Is it possible to test with the nRF54L15DK?

Regards,
Amanda H.

RE: Channel Sounding with Two Antennas: Data Dropouts after Adding Second Path (2 antenna)

witc — Fri, 01 Aug 2025 14:21:38 GMT

Actually, the results do not come in a regular interval – sometimes there are long gaps and it is not stable at all. Even with only one antenna, it maybe works a bit better at the start, but after a few seconds the results become even more unstable. Even though I think my hardware is good, at a distance of 1 meter the results often drop out and are not stable. I set the CS parameters mostly by guessing, because I do not know how to make it more robust, but I did not see any big improvement compared to the default settings. My hardware is a custom board and HOLYIOT-24005 with nRF54L15 – both behave almost the same.
I use ncs 3.0.1