Help on Noise Power

Chan_Loss = 1;

y_mod_am_chan = y_am_mod/Chan_Loss; % signal after channel attenuation/loss

% a_int_sig = 5e-2; % amplitude of interference signals

% f_int_sig = [10e3, 20e3, 25e3, 32e3, 40e3]; % frequencies of interference signals

% int_sig = a_int_sig*sin(2*pi*f_int_sig(1)*time');

% for f_int = f_int_sig(2:end)

% int_sig = int_sig + a_int_sig*sin(2*pi*f_int*time');

% end

signal_power = std(y_mod_am_chan); % Signal Power

noise_power = 0.01*signal_power; % noise power

noise_sig = randn(no_of_pnts, 1)*noise_power; % noise signal generated based on normal distribution

y_mod_am_int = y_mod_am_chan; % received signal with interference signals

You need to geneterate the same plots for all noise powers (0.01, 0.1, 0.5, and 1 times the received signal power at the receiver).

Basically you need to change the coefficient value in

noise_power = 0.01*signal_power; % noise power

line in your channel section.

Answer 1

[Sulaymon Eshkabilov]

If understood correctly, what you are trying to attain is to generate a few different noise powers from the given signal. If so, then

t = (0:0.05:10)';
x = sin(t);
SNR = [0.01, 0.05, 0.1, 1, 10, 50];
LC = 'kbmgck';
for ii = 1:numel(SNR)
    % White noise is generated with awgn():
y_noise = awgn(x,SNR(ii), 'Measured'); % Assumes that the input signal power value in dBW
figure(ii)
plot(t,x, 'r',"LineWidth",2, "DisplayName",'Measured data')
hold on
plot(t,y_noise, LC(ii), 'LineWidth', 1.25, "DisplayName",'Noise added signal')
title(['SNR Level is ' num2str(SNR(ii)) ' dB'])
legend('Show')
end

[Matt]

That is beautiful. Thank you so much.

[Matt]

On the line for ii = 1:numel(SNR) it comes up with the warning: Negative data ignored.

[Sulaymon Eshkabilov]

Most welcome! Glad to be of some help :) Please vote for Thumbs UP :)

[Sulaymon Eshkabilov]

Check your typed in code carefully. It should not produce any warning. Note that numel() does not care about negative or positive values. It counts how many elements in the array.

[Matt]

@Sulaymon Eshkabilov it still does the same issue

[Matt]

@Sulaymon Eshkabilov nevermind, it completely works :)