# SNR to EbNo in OFDM scheme

Started by May 14, 2008
```hey all,

I made an ofdm simulation in matlab, I want it to output Ber/EbNo
plot, and I use the awgn function in order to add white noise in the
channel, and as u know the awgn function requires SNR as input, so I
need to convert from Eb/No to SNR.

I know this:
Es/No(dB)=10log10(Tsymb*Fs)+SNR(dB)

now I need to convert the Es/No of the ofdm signal to Eb/No:
Es/No(dB)=Eb/No(dB)+10log10(Nc*log2(M))+10log10(CodeRate)+10log10(Tinf/
(Tinf+Tcp))

where:
M - number of symbols used in the modulation scheme
Nc - number of subcarriers in the ofdm symbol
CodeRate - well..code rate
Tinf - information period in the ofdm system
Tcp - cyclic prefix period in the ofdm system
(Tcp+Tinf = Tsymbol)

I"m not too sure about the last equation, would like confirmation or
correction

thanks
```
```On May 14, 12:28&#2013266080;am, shach...@gmail.com wrote:
> hey all,
>
> I made an ofdm simulation in matlab, I want it to output Ber/EbNo
> plot, and I use the awgn function in order to add white noise in the
> channel, and as u know the awgn function requires SNR as input, so I
> need to convert from Eb/No to SNR.
>
> I know this:
> Es/No(dB)=10log10(Tsymb*Fs)+SNR(dB)
>
> now I need to convert the Es/No of the ofdm signal to Eb/No:
> Es/No(dB)=Eb/No(dB)+10log10(Nc*log2(M))+10log10(CodeRate)+10log10(Tinf/
> (Tinf+Tcp))
>
> where:
> M - number of symbols used in the modulation scheme
> Nc - number of subcarriers in the ofdm symbol
> CodeRate - well..code rate
> Tinf - information period in the ofdm system
> Tcp - cyclic prefix period in the ofdm system
> (Tcp+Tinf = Tsymbol)
>
> I"m not too sure about the last equation, would like confirmation or
> correction
>
> thanks

SNR = (Eb/No) E[x]^2

Maurice Givens
```