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lincolndsp
Joined: 13 Aug 2005
Posts: 209
Helped: 3
Location: Ukraine
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 25 Mar 2006 7:20 matlab question |
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How can I accurately add to my signal white
gaussian noise of exact SNR in dB (in POWER not
voltage terms)?
when I use awgn(...) function it seems
to me the noise has more power than I
set in its SNR parameter.
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Sal
Joined: 29 Nov 2005
Posts: 291
Helped: 36
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| 27 Mar 2006 22:51 matlab question |
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Added after 24 seconds:
Hi
That is not really true, after adding the awgn to your signal by the awgn() function, you can substract your original signal and then calculate the energy of both signals, this will clear your doubts. Mind the dB conversion.
Sal
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carpa
Joined: 12 Nov 2004
Posts: 82
Helped: 5
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| 28 Mar 2006 6:28 matlab question |
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Y = AWGN(X,SNR) adds white Gaussian noise to X. The SNR is in dB.
The power of X is assumed to be 0 dBW. If X is complex, then
AWGN adds complex noise.
Y = AWGN(X,SNR,SIGPOWER) when SIGPOWER is numeric, it represents
the signal power in dBW. When SIGPOWER is 'measured', AWGN measures
the signal power before adding noise.
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Naveed Alam
Joined: 06 Jan 2006
Posts: 280
Helped: 16
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| 29 Mar 2006 12:05 Re: matlab question |
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hi...
i m giving u somepart of Eric Cosby's program, u can use it to calculate it...
%suppose u have Tx_data, and now u want add awgn noise
SNR=13; % in dB
Tx_signal_power = var(Tx_data);
%
linear_SNR = 10^(SNR/10);
noise_sigma = Tx_signal_power/linear_SNR;
noise_scale_factor = sqrt(noise_sigma);
%
noise = randn(1, length(Tx_data))*noise_scale_factor;
REGARDS
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