title: MATLAB signal up conversion and transmitting over the air
body: <p>I have created an OFDM signal (WLAN) in MATLAB and saved the complex valued signal in a file. I then transfer the file to USRP-B210 (Software Defined Radio) and transmit over the air. Note that in MATLAB, I do not require to up-convert the signal to IF(intermediate frequency), as it is done by the radio device itself.</p>
  <p>The signal is received by the receiver (which down-converts) and saves the file in local disk. I then process the receive file in MATLAB. Everything works perfect, and data is decoded correctly.</p>
  <p>Now, I want to apply a Rayleigh Channel (that has Delay-Doppler effect over multipath channel). MATLAB has built in function for that <a href="https://www.mathworks.com/help/comm/ug/fading-channels.html" rel="nofollow noreferrer">Fading Channel</a>. In such case, my signal transfer works fine with minor degradation in performance (BER). But degrades as I increase Delay-Doppler effect.</p>
  <p>My question is, while I use the channel model, I am not doing any upconversion of the baseband signal before passing it to the channel model function. Was that necessary ? Because applying channel model on the base band sounds incorrect. In that case what other options do I have ?</p>