During transmission of the OFDM
signal, the
symbols
will be multiplied by the
window
*w*(*t*) and not
by

*w*^{2}(*t*). The spectra of the pulses
*w*(*t*)
have no zero-crossings at integer
values
of 1/T as it happens with *w*^{2}(*t*)

-it only happens
for the particular case of the rectangular window, because in this case *w*(*t*) = *w*^{2}(*t*)-. The orthogonality is achieved at the receiver side
by multiplying
the incoming signal
by *w**(*t*). The information sequence *A*_{k }is obtained after multiplication by the corresponding complex conjugated phasor and integrating
over an interval T(1+a_{r}), as shown in Figure
2.13. In Figure 2.14, the spectrum of
an OFDM signal
with *A*_{k}=1

'*k *and N=32 is represented. There it can be better appreciated the dependency of the total bandwidth of the OFDM signal
with respect
to the selected window. Clearly, the root raised cosine (RRC) window results in
the better bandwidth efficiency among the proposed windows.