Channel Sounding with nRF54L15 – Poor Accuracy Compared to Nordic's Demo

[Ibai]

Hi Nordic team,

I'm currently working on a real-time distance measurement project using channel sounding with the nRF54L15 DKs. I’ve been using the channel_sounding_ras_initiator and channel_sounding_ras_reflector samples from your official GitHub repository, and I’ve managed to get the system running successfully.

However, the performance I’m getting in terms of distance accuracy and responsiveness is noticeably worse than what’s shown in your YouTube demo (https://www.youtube.com/watch?v=dbQKqXN80ms). In your video, the distance tracking appears smooth and accurate, even when the devices are in motion.

In my case, the measurements are much more noisy, and there’s a significant delay (sometimes several seconds) between physical movement and updated distance readings. I’ve only made minor modifications to the sample code—such as increasing buffer sizes and applying a median filter to reduce noise.

My questions are:

1. Is the code used in the YouTube demo exactly the same as the channel_sounding_ras_initiator and channel_sounding_ras_reflector samples, or was it modified for the demo?

2. Are there specific hardware requirements or environmental conditions (e.g., antenna placement, orientation, shielding) that are crucial for achieving the best performance?

3. Is any calibration or parameter tuning needed beyond what is included in the sample projects?

I’d really appreciate any tips or insights on how to get results closer to what you demonstrate in the video.

Thanks in advance,

Ibai

[SwRa]

Hello,

Which version of the nRF Connect SDK are you using.? You need to use the version 3.0 and using the IFFT.. 

I’ve only made minor modifications to the sample code—such as increasing buffer sizes and applying a median filter to reduce noise.

You don't need to do this if you are using v3.0 of the SDK as it has the filter. Also, make sure you are using the nrf samples and not the ones in Zephyr: https://docs.nordicsemi.com/bundle/ncs-3.0.2/page/nrf/samples/bluetooth/channel_sounding_ras_initiator/README.html and https://docs.nordicsemi.com/bundle/ncs-3.0.2/page/nrf/samples/bluetooth/channel_sounding_ras_reflector/README.html 

Best Regards,

Swathy

[Hay]

I have a similar impression when running the same samples without modifications in the latest nrf sdk version (also tried stepping back to 3.0 exactly) with two nrf54l15dk. The IFFT value is much better than the PBR and RTT value, and it seem fairly good at times when the initiatior and reflector are oriented towards each other and nothing else is obstructing them. But just some small adjustment can make the value jump by several meters at times or when I walk around in a room it's off by several meters. I suspect the demo was in quite good conditions, but I can't say for sure.

Based on my reading of appnotes from other manufacturers is that you need more antenna paths for good accuracy. Two antennas on either side seems to be a sweet spot, then you get four antenna paths in total. As far as I understand, Nordic supports multiple antennas in software, but has no hardware for it (or any hardware reference designs or recommendations).

Also, the algorithm that calculates the distance from the raw values play a role. I don't know how big compared to the antenna setup at this point, but there are companies focusing on just developing proprietary algorithms for this. Nordic's efforts towards this appears to be a work in progress with some significant improvements made in 3.0.

Someone from Nordic, please correct me if I'm wrong.

[Ibai]

Hi Swathy,

Thanks for your response.

I can confirm that I’m using nRF Connect SDK version 3.0.2, and I’m working with the official Nordic samples (not the Zephyr ones), specifically:

• channel_sounding_ras_initiator

• channel_sounding_ras_reflector

When both boards are stationary and facing each other, the distance estimations are quite accurate and stable. However, when either board is in motion, the measurements become significantly more noisy and fluctuate a lot. This makes real-time tracking unreliable in dynamic scenarios.

Do you have any recommendations on improving performance while moving? For example, would increasing the measurement rate or using specific antenna orientations help?

Thanks for your support.

[PaKa]

Please define "significantly more noisy and flucutate a lot". This to be able to determine if this is inside expecations or not.

[Ibai]

Hi again,

Thanks for your follow-up.

To clarify what I mean by "significantly more noisy and fluctuating":

When both boards are placed facing each other and the reflector moves linearly and steadily toward the initiator, the IFFT-based distance estimations are not behaving as expected. Specifically:

• The measured distance sometimes increases, even though the reflector is clearly moving closer to the initiator.

• Additionally, the measurements show high variability, with noticeable fluctuations even when the movement is smooth and at a constant speed.

This inconsistent behavior occurs despite maintaining proper alignment and a clear line of sight between the boards. When both boards are stationary, the estimations are much more stable and accurate.

Is this deviation expected in dynamic scenarios, or could it be related to how the IFFT processing handles movement?

Thanks again for your support.