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Re: [Discuss-gnuradio] BER over air

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] BER over air
Date: Mon, 29 Dec 2014 13:12:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0

Hello Mostafa,
On 12/29/2014 12:55 PM, Mostafa Alizadeh wrote:
I finally got to this point that if one need to measure SNR, it means that he/she has to eliminate all the other channel effects as well as receiver uncertainties, (like fading, shadowing, Doppler shift, carrier frequency and phase offsets etc.) to have a correct estimate of SNR.
SNR is relative to signal. Signal is what you define it to be. You can say "I measure my SNR after equalizing and perfect synchronization", you could also say "the power of the signal coming out of the receiver amplifier relative to the noise generated in that amplifier, before any filtering". It's all up to your definition. I will never cease to repeat that.

There is no physical entity SNR to measure. When you say "SNR is XY dB", it is utterly meaningless unless you define what your signal is and where in your signal processing chain you determine the SNR.
Otherwise, he/she coudln't obtain signal-to-noise power ratio. 

Remember the received signal formulation I mentioned before: 
y(t) = h(t) * x(t) + n(t).

Thank you all. Any interesting ideas would be appreciated.
... you're still asking for easy ideas how to solve your problem which is complicated. You will have to accept the fact that SNR is not a universal measure with a "right" way to measure for any kind of signal, any kind of channel, any kind of system.


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