On Apr 7, 6:33 pm, "Crisanquito" <crisanc...@hotmail.com> wrote:
> Hello
>
> I just want to know if the computations I do to know the relation
> Energy_per_Bit/No are correct in the next situation: I add white noise
> after performing the FFT in a OFDM receiver as shown next:
>
> Signal_Power=var(Noiseless_Signal_in_Frequency);
> VarianceNoise=SNR/Signal_Power;
> Noisy_Signal=Noiseless_Signal_in_Frequency+sqrt()*(randn()+1i*randn())...;
>
> Is the Energy_per_Bit/No relation computed as:
>
> Energy_bit=(Signal_Power/Number_Subcarriers)*1/(OFDM_Symbol_Duration*Number_Subcarriers)*1/log2(4)
> (QPSK)
>
> No=NoiseVariance/Signal_Bandwidth
>
> ?
It looks like Signal_Power is per OFDM carrier and per OFDM symbol. In
that case,
Energy_per_bit = (Signal_Power*Number_Subcarriers)*1/
(OFDM_Symbol_Duration*Number_Subcarriers*2)
You have a typo above in the Noisy_Signal formula, but I think you
mean:
Noisy_Signal=Noiseless_Signal_in_Frequency+sqrt(NoiseVariance/2)*(randn
()+j*randn())
where NoiseVariance=N0*Signal_Bandwidth
Otherwise, your formulae are correct.
Thanks,
Dilip.
Reply by Crisanquito●April 7, 20092009-04-07
Hello
I just want to know if the computations I do to know the relation
Energy_per_Bit/No are correct in the next situation: I add white noise
after performing the FFT in a OFDM receiver as shown next:
Signal_Power=var(Noiseless_Signal_in_Frequency);
VarianceNoise=SNR/Signal_Power;
Noisy_Signal=Noiseless_Signal_in_Frequency+sqrt()*(randn()+1i*randn())...;
Is the Energy_per_Bit/No relation computed as:
Energy_bit=(Signal_Power/Number_Subcarriers)*1/(OFDM_Symbol_Duration*Number_Subcarriers)*1/log2(4)
(QPSK)
No=NoiseVariance/Signal_Bandwidth
?