No, the number of subcarriers and FFT size can be different as long a subcarriers are less than the FFT size. Usually the channel dictates how you populate the bins; for eg: in a high doppler channel the data subcarriers are usually interlaced with "OFF" subcarriers. hope this helps
j...@yahoo.co.in wrote: I am doing a project related to OFDM. My doubt
is whether the no of subcarriers and the IFFT size should be equal or not?