[USRP-users] Estimate the SNR at the receiver

Martin Braun martin.braun at ettus.com
Wed Jul 5 14:59:23 EDT 2017


On 07/04/2017 01:10 PM, Βασίλης Τσέκενης via USRP-users wrote:
> Hello everyone, 
> 
> It's the third time that I post something here and I would like to
> express my thankfulness because reading Questions/Answers helped me in
> completing my bachelor thesis in MIMO-OFDM systems using USRP N210 and
> MATLAB.
> 
> At the time, I have 3 final questions to solve (in MATLAB) and I would
> be glad if someone can help me. 
> I am sending OFDM packets (bursts), receive them, keep one burst,
> synchronize (with preamble) and demodulate correctly. 
> 
> 1) I would like to know how to find SNR at the receiver without any
> build-in function of MATLAB. I came up with energy detector (I heard I
> can find SNR also with this) but it didn't help me so I use sync based
> on preamble. 
> 2) What it the Transmin Power of USRP? I can only adjust Tx and Rx
> gain.. (Try to confirm Free Space Loss Model)
> 3) Is there an easy method to find Banwidth of transmitted signal?

Basil,

all three questions are not something we can answer for you,
unfortunately. Estimating SNR is a hard problem, and there are
algorithms, typically tied to the waveform you're receiving (e.g., OFDM
would have different algos than SC QPSK, etc.).

The transmit power depends on many things, and USRPs are not calibrated,
so you would need to measure the feed going into your antenna using a
calibrated power meter or spectrum analyzer (and then factor in data
from your antenna).

The bandwidth however is a function of the signal you provide. You
should be able to calculate that.

Cheers,
Martin




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