OFDM modulation is applied in the frequency domain. Figure 2 and Figure 3 give an example of modulated OFDM carriers for one symbol period, prior to IFFT. For this example, there are 4 carriers, the IFFT bin size is 64, and there is only 1 bit per symbol. The magnitude of each carrier is 1, but it could be scaled to any value. The phase for each carrier is either 0 or 180 degrees, according to the symbol being sent. The phase determines the value of the symbol ( binary in this case, either a 1 or a 0). In the example, the first 3 bits (the first 3 carriers) are 0, and the 4th bit (4th carrier) is a 1.
-------------------------------------------------------------------------------------------------------------------------------------
figure (2)
%plot(0:IFFT_bin_length-1, (180/pi)*angle(IFFT_modulation(2,1:IFFT_bin_length)), 'go')
%hold on
%stem(carriers-1, (180/pi)*angle(IFFT_modulation(2,carriers)),'b*-')
%stem(conjugate_carriers-1, (180/pi)*angle(IFFT_modulation(2,conjugate_carriers)),'b*-')
%axis ([0 IFFT_bin_length -200 +200])
%grid on
%ylabel('Phase (degrees)')
%xlabel('IFFT Bin')
%title('OFDM Carrier Phase')
% END OF PLOTTING
%
% Transform each period's spectrum (represented by a row of carriers) to the
% time domain via dddmy/p>
%
time_wave_matrix = ifft(IFFT_modulation');
time_wave_matrix = time_wave_matrix';
%
% PLOT OFDM SIGNAL FOR ONE SYMBOL PERIOD
% - first plot is direct IFFT of first OFDM symbol (index 2)
% - index 1 is the 'start' symbol due to differential implementation
% - second plot strips out each carrier and plots them on the
% same graph
% - only works for carrier count <= 16 due to colors variable (more
% than 16 would really be legible anyway
上面是程序和英文资料，版主等你有空能帮忙大概看下吗？谢谢了！