generating AWGN in matlab

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michael
michael 2013-8-22
编辑： Walter Roberson 2015-8-30
I'd like to have your overview if what I'm doing is OK.
I need to plot the BER vs Eb/No. So the noise power which I should generate should be related to Eb/No.
  1. bits are encoded into 1/2 rate encoder.
  2. the output of the encoder is converted to +1 and -1 symbols
  3. symbols are oversampled by OS ratio.
  4. the oversampled symbols are passed through Gaussian filter and this is the data which i send to the channel.
now i need to generate AWGN:
EbNo_dB_bit_list = -2:0.25:2;
EsNo_dB_no_code = EbNo_dB_bit_list - 10*log10(OS);
dec_EsNo_dB_no_code=10.^(-EsNo_dB_no_code/10);
sigma2 = 1/(2*Rate)*dec_EsNo_dB_no_code; % to include the code rate
ni = randn(1,length(modulated));
nq =randn(1,length(modulated));
noise=(ni+1j*nq)*sqrt(sigma2(k));

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回答（2 个）

Bhavik Doshi
Bhavik Doshi 2013-8-22
编辑：Walter Roberson 2015-8-30
clc; close all; clear all; sym=1000; snr=30; M=2;
msg=randi(1, M-1,sym) mod=pskmod(msg,M); for i=0:snr yn=awgn(mod,i); msgbar=pskdemod(yn,M); [a(i+1) b(i+1)]=biterr(msgbar,msg); end semilogy(0:snr,b,'r'); grid on title('Simple AWGN'); xlabel('Eb/No'); ylabel('BER');
  2 个评论
Bhavik Doshi
Bhavik Doshi 2013-8-22
Separate lines after ;
michael
michael 2013-8-22
sorry, but i don't understand your answer. you have provided code for BER of BPSK. I need to have conformation that my steps in noise generation is OK

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Bhavik Doshi
Bhavik Doshi 2015-8-30
Let us consider that final signal this coded as x matrix. Assumption: x is a mxn matrix. x is already over sampled x is already modulated and coded as per requirement you need y = xh + n where h is complex channel and n is noise.
Now, as you mentioned, you do not need h, assuming wired transmission.
y= x+n.
Matlab implementation:
y = awgn(x, snr);
use x as your coded modulated signal matrix or vector. snr = choose value between 0 to 30 db only.

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