Channel Sounding Distance accurancy issue

[Fhar]

Hello Support Team,

I am currently testing the new Channel Sounding feature on two nRF54L15 boards, on which I flashed your Channel Sounding samples (initiator and reflector).
I noticed that the distance accuracy (for example, using the IFFT) is not as precise as I expected (see the graph below). 

I tested with real distances of 5 m and 4.5 m, but the measured values were significantly different — with more than 4 m of error for the 4.5 m test. I am a bit confused about this behavior.

I also performed a test at 13 m in another environment, this time with more Bluetooth devices nearby that could generate interference. However, the IFFT results were very irregular, and I find it difficult to understand its behavior.

Do you have any idea what could cause this inaccuracy ?

For these tests, I was in a typical indoor environment.
The only change I made in the code was adjusting the sleepins time from 5 s to 1 s.
I am using NCS version 3.1.0.

Thank you for your help

[PaKa]

It looks like what is called "average" is actually a median filter. This works differently as outliers are ignored totally while in average they will impact the results. You use median filters here as one of the quirks of phase based ranging is that you can get suddenly get very wrong results caused by for instance multipath. With a median filter these are removed while with average they would "count".

More advanced and tailored filtering can also be used if you need even better performance