To reduce out of band energy, it is common to apply a Raised Cosine filter to the front and back of an OFDM symbol. It is also common to overlap the windowed portions of adjacent symbols to eliminate amplitude dips.
For an OFDM symbol consisting of a Cyclic Prefix followed by NFFT points from an IFFT, is it common to insert an additional prefix and suffix for the windowed portion? If that isn't done then the CP and the IFFT data are shaped by the window, distorting the constellation. A pretty good description of what I am talking about is here: