OFDM simulation

hi all

I hope that you can help me.

I actually have to simulate an ofdm system to show the graph of magnitude
against frequency. I am however stuck...

part my initial codes are as follows:


        % generating 400 symbols (block 20 x 20)->transmitted signal
        qpsk= exp(j*[pi/4 3*pi/4 5*pi/4 7*pi/4]');
        s=qpsk(randint(20,20,4)+1);
        
        %convert to time domain
        x=ifft(s);
        
**** this is where i need to show the graph****

Can anybody kindly help me. i can say that im stuck at this point.

thanking you for your assistance

sheen

On Oct 24, 4:30 am, "sheen2411" <nawshee...@hotmail.com> wrote:
> hi all
>
> I hope that you can help me.
>
> I actually have to simulate an ofdm system to show the graph of magnitude
> against frequency. I am however stuck...
>
> part my initial codes are as follows:
>
>         % generating 400 symbols (block 20 x 20)->transmitted signal
>         qpsk= exp(j*[pi/4 3*pi/4 5*pi/4 7*pi/4]');
>         s=qpsk(randint(20,20,4)+1);
>
>         %convert to time domain
>         x=ifft(s);
>
> **** this is where i need to show the graph****
>
> Can anybody kindly help me. i can say that im stuck at this point.
>
> thanking you for your assistance
>
> sheen

Sheen,

You need to stop what you are doing and think about what you want to
show.  You give the impression that if the graph isn't shown in that
particular part of your code progression, then the sky is falling
down.

So, you would like to plot magnitude versus frequency.  Let me ask you
two questions.

1) How would you define the magnitude of your complex symbols (qpsk)?
2) If you are converting to the time domain, with x=ifft(s); then what
domain is the vector s in prior to conversion?

If you can answer those two questions, then you can plot magnitude
versus freq very easy.

col