This tutorial shows the idea of analog time domain OFDM. My question is if we can sample the analog signal and use time-domain OFDM in a similar fashion. Why do we need to apply IFFT/FFT to the signal at transmitter/receiver?
I understand that it is more efficient to use the FFT at the receiver side, but why do we transform the original data to a complex number by some modulation technique and then use the IFFT (instead of just sending it in the time domain)? There has to be some benefit beyond efficiency.