Hello zburcin,
I understand that you are trying to perform Channel Estimation in OFDM. Making the following changes to your code will resolve the issue.
- Multiplication in the DFT domain is equivalent to circular convolution in the discrete-time domain. You can substitute “yhat2 = conv(x_ifft1,channelTD.');” with “yhat2 = cconv(x_ifft1,channelTD',nfft);”
- Setting Signal Power to 1, should be done for transmitted signal not for received Signal. Please remove the “yhat2 = yhat2 / sqrt(var(yhat2));” line from your code.
- As the Cyclic Prefix is not being added, we do not need to shift the signal. You can remove the “fftshift” from the following lines.
a. x_ifft1 = sqrt(nfft) * ifft(fftshift(qamSig),nfft);
b. y_fft2 = (1/sqrt(nfft))*(fft(fftshift(yhat2),nfft));
Note that the data in “EstimatedChannel” variable will be in the frequency domain.To directly compare it with the data in “channelTD.mat,” conversion to time domain by using “fft” is necessary.
You can find more information about the “cconv” function here, https://in.mathworks.com/help/signal/ref/cconv.html.
