# How can I oversample OFDM received signal in MATLAB

I need to oversample a received signal in OFDM by MATLAB, according to the below diagram, but when I oversample, I finally get the same number of samples however that should be double. !! The oversampling should be done after receiving the signal, .. as below

Could you please explain how can I do that resampling in MATLAB? I mean after receiving the signal, which is y = conv(x,h) + n; where x is the transmitted signal and h is the channel, and n is white noise. so. how can I perform the resampling for y ?

here is what I tried to do :

Y_r = resample(R,2,1);   %% R is the received signal
ty = (0:(length(Y_r)-1))*1*Ts/2;
Y_r_new=exp(-1i*2*pi*Fc*ty).*Y_r;   %the oversampled signal.


OK, till now is ok, but when I run this command, in the first time I put Y_r_new is the oversampled signal, and then change it into Y_r_old which is the original signal, I get an output with same length !!:

for isij=1:Numsymbol     %%Numsymbol      is the number of symbols

R_D_fil_be=Y_r_new(1,(isij-1)*L_perOFDM+1:isij*L_perOFDM);  %%L_perOFDM is number of carrier multiplied my symbol.
end

• This is a lot to read and digest-- are you able to pull out a much simpler version of your code specific to your problem? Have you tried such a simpler case? I'm not sure you need all this detail to ask your question or find your problem. – Dan Boschen Aug 10 at 10:11
• OK , the question, how can I make sampling for received OFDM signal? I mean according to the above first code, where should I do the sampling .. – Eng. Badr Aug 10 at 12:23
• If you are simulating the Tx waveform and the channel, it should be sampled right in the beginning following Nyquist criteria to be at least twice the overall bandwidth of your channel. Typically you sample even higher to allow for a finite filter roll-off. – Dan Boschen Aug 10 at 12:27
• OK, thank you .. so according to the code above, where should I perform the sampling, is that right what I am doing ? I'm talking about sampling when receiving the signal. I'm not talking about the transmitter.. – Eng. Badr Aug 10 at 12:44
• Your sampling is defined by Ts, whether it is high enough would depend on your waveform. I wouldn't really be able to figure that all out from reading your code. Could you perhaps add a block diagram to the beginning of your post that shows the spectrum your waveform occupies in Hz, and the sampling rate you are choosing (the actual numbers you are using not variables)? – Dan Boschen Aug 10 at 12:50