Distortion of OFDM signal when using RRC filter I am trying to transmit OFDM signal in pass-band based on RRC filter, but what I noticed that the signal before the RRC filter is completely different compared with signal after the RRC filter (It means the signal is destroyed when using RRc filter).  I tried to follow the signal without using any channel, I noticed the issue starts when using the RRC filter. For example,  I used only the system as follows:
signal --&gt; ifft --&gt; upsampling --&gt; RRC filter --&gt; RRC filter --&gt; downsampling --&gt; fft --&gt; received signal

What is expected is the received signal equals to signal, but I get very different results.
what I get is a different signal. Why ? should that be equal? I think I must be the same.
Finally , when I delete the filter, Everything is OK.
I checked your code in my PC, you need just to delete the delay added before the filter. For example, you can use:
U_aft_fil = U_aft_fil(fil_delay+1:end);  

Then when filtering it again at the receiving side, you delete it again :
U_r_fil = U_r_fil(fil_delay+1:end);

Good luck