Use of the STD_NOISE value

Wireless Connectivity Ultra-Wideband
1

Hi All,

I am working on a project where I want to use the received frame quality for determining if that particular ranging measurement is likely to be good quality first path LOS measurement or not. I read the section 4.7 Assessing the quality of reception and the RX timestamp. A part that confused me, however, is the use of STD_NOISE value.

The description says it is the standard deviation of the noise. How do we use this value? Instead, if the average magnitude of noise was reported, it could be directly compared with FP_AMPL2 (by taking a ratio akin to SNR). Has anyone used this value? Is it really the standard deviation of the noise (all CIR taps before FP)?

Edit: Is the term “standard deviation” used to be synonymous of “root mean square” in the documentation? That would make perfect sense for zero mean noise.

Thanks and Regards,
-Ashutosh

2

Hey Ashutosh,

as far as I know yes it is the standard deviation of the noise (please someone from Decawave correct me if I am wrong), hence, CIR taps before FP. But you can easily check that by yourself.

No why should ‘standard deviation’ be the same as ‘root mean square’?

And be careful by calling FP_AMPL2 / STD_NOISE the SNR, this is not correct.

BR,
Bernhard

3

Hi, All is well described and explained in our application note APS006 Part 3 , which you can download from our website under Range and Accuracy.

4

Thanks a lot, Bernhard and Leo,

I calculated the noise from the CIR and indeed the reported standard deviation of noise is close to the std(CIR[0…fp_index-1]).

So I did not use the STD_NOISE value and I will no longer call (FP_AMPL/STD_NOISE) the SNR.

Leo,
I had not read the AP006 Part3 before. It is an extremely useful document. Thanks for sharing it.

-Ashutosh

5

Hi, I’ve also read the AP006 Part3 document and I agree it is very useful. Nevertheless, I have a question: with this document we can, roughly speaking, understand if a ranging is LOS/NLOS, but how can I compute a SNR measurement, related on, e.g., electromagnetic noise regardless of LOS/NLOS scenario?