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adding noise to an oversampled ofdm signal

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Mishaal

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Hi All,

I'm really in trouble because of this awgn. I am trying to add noise awgn to oversampled ofdm signal. my signal is oversampled 20 times and modulated on a high frequency carrier. After applying band pass filter I have tried to do this

SNR = EbNo + 10*log10(k) - 10*log10(upsamp)
corrupted = awgn(usig, SNR,'measured','dB');

where upsamp is 20, and k is 2, two bits per symbol with QPSK modulation,,,

am I doing anything wrong,,,,,

this results me no error in the signal with the higheer values of noise even,,,,

please help me ,,,,,what should i do,,,i tried the same thing with baseband ofdm signal as well, but same result,,

Thanks

Regards
 

Would really like to help but I do not understand your code
This is what o used for QPSK and it worked for me:
SNR =1:1:30; % SNR in dB
index_SNR =1:1:length(SNR)
noisy=awgn(sig,index_SNR,'measured');

hope it gives you some directions...
 

Hi,

The SNR definition there you can look at it as SNR_bit=Eb/N0=(SNR_symbol)*(W/R), where R is your rate and W is the bandwidth.
Now, you for R = Symbol Rate * modulation = (20*W*log2(M)), here W is the normal bandwidth and M is your modulation i.e. M=2 for QPSK.
so we have R=20*W. Then SNR_bit(dB)=SNR_channel-10log(20), which would be your SNR computation.

you can plug the channel SNR into the AWGN with the tx ofdm output.

Have Fun!
 

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