Communication Technology

OFDM Details

hMod = comm.OFDMModulator;

hMod.InsertDCNull = true;

hMod.PilotInputPort = true;

hMod.PilotCarrierIndices =[14; 24; 42; 52];

hModInfo = info(hMod);

 

rng(0);

dataIn = complex(ones(hModInfo.DataInputSize),ones(hModInfo.DataInputSize));

PilotIn = 1.5 * complex(ones(length(hMod.PilotCarrierIndices),1), ...

                        ones(length(hMod.PilotCarrierIndices),1));

modData = step(hMod,dataIn,PilotIn);

 

modDataNoCP = modData(length(modData)-hMod.FFTLength+1:length(modData));

modDataNoCPfft = fftshift(fft(modDataNoCP));

 

indicesOfPilotAndDC = [hMod.PilotCarrierIndices ; length(modDataNoCPfft)/2+1];

indicesWoPilotAndDC = [ ];

 

for i = 1:length(modDataNoCPfft)

   if ismember(i, indicesOfPilotAndDC) == 0

    indicesWoPilotAndDC = [indicesWoPilotAndDC i];

   end;

end;

 

modDataNoCPfftNoPilotDC = modDataNoCPfft(indicesWoPilotAndDC);

modDataNoCPfftNoPilotDcNoGB = modDataNoCPfftNoPilotDC(hMod.NumGuardBandCarriers(1)+1 : ...

                                    length(modDataNoCPfftNoPilotDC) - hMod.NumGuardBandCarriers(2));

 

                               

hDeMod = comm.OFDMDemodulator(hMod);

hDeModInfo = info(hDeMod);

 

[deModData,PilotOut] = step(hDeMod, modData);

 

subplot(7,1,1);

stem(abs(dataIn));xlim([1 length(dataIn)]);

title('Input Data');

set(gca,'xtick',[1 length(dataIn)]);

 

subplot(7,1,2);

stem(abs(modData));xlim([1 length(modData)]);

title('Mod Data');

set(gca,'xtick',[1 length(modData)]);

 

subplot(7,1,3);

stem(abs(modDataNoCP));xlim([1 length(modDataNoCP)]);

title('Mod Data - CP Removed');

set(gca,'xtick',[1 length(modDataNoCP)]);

 

subplot(7,1,4);

stem(abs(modDataNoCPfft));xlim([1 length(modDataNoCPfft)]);

title('ShiftFft(FFT(Mod Data - CP Removed))');

set(gca,'xtick',[1 length(modDataNoCPfft)]);

 

subplot(7,1,5);

stem(abs(modDataNoCPfftNoPilotDC));xlim([1 length(modDataNoCPfftNoPilotDC)]);

title('ShiftFft(FFT(Mod Data - CP Removed)) -Pilot/DC Removed');

set(gca,'xtick',[1 length(modDataNoCPfftNoPilotDC)]);

 

subplot(7,1,6);

stem(abs(modDataNoCPfftNoPilotDcNoGB));xlim([1 length(modDataNoCPfftNoPilotDcNoGB)]);

title('ShiftFft(FFT(Mod Data - CP Removed)) - Pilot/DC/GuardBand Removed');

set(gca,'xtick',[1 length(modDataNoCPfftNoPilotDcNoGB)]);

 

subplot(7,1,7);

stem(abs(deModData));xlim([1 length(deModData)]);

title('Demod Data');

set(gca,'xtick',[1 length(deModData)]);