adding noise to an oversampled ofdm signal

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 

mishal81 wrote:

> 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 

On Thu, 09 Feb 2012 08:44:42 -0600, mishal81 wrote:

> 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,,

It appears that you are blindly applying Matlab toolbox functions with no 
idea of what they mean.

Try this:  Let your signal be x.  Make a noise vector of random, normal, 
zero-mean samples that's the same size as x.  Add the noise vector to x.  
Then proceed.

Or, if you want to understand what Matlab is doing, use 'awgn' to corrupt 
the signal (I assume that's what it does), then subtract your real signal 
from the corrupted signal.  This should be the noise that was added, and 
you can verify that it is Gaussian, white, etc., -- in other words, you 
can figure out just what Matlab is doing when it does that function.

And for heaven's sake -- learn signal processing, not just Matlab button-
pressing!

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Feb 9, 12:59&#4294967295;pm, Tim Wescott <t...@seemywebsite.com> wrote:
> On Thu, 09 Feb 2012 08:44:42 -0600, mishal81 wrote:
> > 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,,
>
> It appears that you are blindly applying Matlab toolbox functions with no
> idea of what they mean.
>
> Try this: &#4294967295;Let your signal be x. &#4294967295;Make a noise vector of random, normal,
> zero-mean samples that's the same size as x. &#4294967295;Add the noise vector to x.
> Then proceed.
>
> Or, if you want to understand what Matlab is doing, use 'awgn' to corrupt
> the signal (I assume that's what it does), then subtract your real signal
> from the corrupted signal. &#4294967295;This should be the noise that was added, and
> you can verify that it is Gaussian, white, etc., -- in other words, you
> can figure out just what Matlab is doing when it does that function.
>
> And for heaven's sake -- learn signal processing, not just Matlab button-
> pressing!
>

probability of solving problem within proper time by first learning
signal processing:

0% = a

probability of solving problem within proper time by matlab button
pushing

>0% =b

b-a = +epsilon?


learning signal processing