I understand to obtain a real output from IFFT, its input has to be conjugate symmetric. In 802.11a, 64-point IFFT is used with 48 data carriers and 4 pilot carriers. If all the 48 data carriers are carrying data then where are its conjugate carriers?
48 data carriers or 24 in 802.11 OFDM transmission?
Started by ●December 2, 2005
Reply by ●April 12, 20062006-04-12
In fact, in 802.11a, it does not use the symmetric conjugate technique, i.e., the output of IFFT module is not the real signal, but complex siganl. Why they did this? Because 802.11a uses the carrier modulation technique, whos e central carrier frequency is 5 GHz. In application, as I know, ADSL1 uses the symmetric conjugate input of IFFT module, also in MB-UWB system case as well.