SNR in AWGN

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oblivious
oblivious 2012-6-10
回答： philip 2023-10-11
Hello,
i am trying to do some simulation of AWGN channel. matlab has a function awgn(x,snr). what kind of snr does it use here? is it Eb/No (average bit energy/power spectral density)? If so, then i know the awgn has a PSD equal to No/2. does that psd in the snr term implies No/2?
-OBLI

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Darel
Darel 2021-8-4
The function awgn does not use EbNo. It uses SNR, defined in the same manner as the snr() function from the Signal Processing Toolbox: sum of the squared samples of the signal over sum of the squared samples of the noise, where that ratio is converted to dB. Thus, if you created noisy data according to
y = awgn(x, SNR);
you should be able to check that
mySNR = snr(x, y-x)
is about the same as SNR in the first call.

更多回答（2 个）

Wayne King
Wayne King 2012-6-10
With the syntax
y = awgn(x,snr);
You generate a white noise vector with a variance of
variance = 10^(-snr/10);
noise = sqrt(variance)*randn(size(x));
If you use 'measured', then awgn actually measures the signal power.
For example:
x = cos(pi/4*(0:99));
y = awgn(x,5,'measured');
In this case the variance of the additive white noise is:
sigp = 10*log10(norm(x,2)^2/numel(x));
snr = sigp-5;
noisep = 10^(snr/10);
noise = sqrt(noisep)*randn(size(x));
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Mustafa qays
Mustafa qays 2017-11-14
The calculation is correct but the variable names need to be corrected
Signal to noise ratio SNR = sigp/noise_p (in ratio)
or
SNR = sigp - noise_p (in dB)
=>
noise_p(dB) = sigp - SNR , SNR = 5 dB
noise_p(db) = sigp - 5
noise_p = 10^(noise_p(db)/10)
So , (snr) in his equation should be written as noise power in the last section of code
Mrutyunjaya Hiremath
Mrutyunjaya Hiremath 2020-9-13
Meaningful Explanation

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philip
philip 2023-10-11
x = cos(pi/4*(0:99));
y = awgn(x,5,'measured');

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