OFDM Modulator

Creating OFDM Modulator

hMod = comm.OFDMModulator;

hModInfo = info(hMod);

 

hMod

Properties:                FFTLength: 64        NumGuardBandCarriers: [6;5]             InsertDCNull: false           PilotInputPort: false       CyclicPrefixLength: 16                   Windowing: false               NumSymbols: 1          NumTransmitAntennas: 1

 

hModInfo

DataInputSize: [53 1]       OutputSize: [80 1]

FFTLength = NumGuardBandCarriers(1) + DataInputSize +  NumGuardBandCarriers(2) = 6 + 53 + 5 = 64

OutputSize = FFTLength + CyclicPrefixLength = 64 + 16 = 80

Generating OFDM Symbol Data with Default Setting

hMod = comm.OFDMModulator;

hModInfo = info(hMod);

 

rng(0);

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

modData = step(hMod,dataIn);

 

subplot(2,1,1);

stem(abs(dataIn));xlim([1 length(dataIn)]);title('Input Data');

subplot(2,1,2);

stem(abs(modData));xlim([1 length(modData)]); title('Output Data');

Generating OFDM Symbol Data with Internal Procedure

hMod = comm.OFDMModulator;

hModInfo = info(hMod);

 

rng(0);

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

dataInGuardBand = [zeros(hMod.NumGuardBandCarriers(1),1); ...

                           dataIn; ...

                           zeros(hMod.NumGuardBandCarriers(2),1)];

dataInGuardBandIfft = ifft(dataInGuardBand);

CP = dataInGuardBandIfft(length(dataInGuardBandIfft)-(hMod.CyclicPrefixLength)+1: ...

                                   length(dataInGuardBandIfft));

dataInGuardBandIfftCP = [CP ; dataInGuardBandIfft];

 

modData = step(hMod,dataIn);

 

subplot(5,1,1);

stem(abs(dataIn));xlim([1 length(dataIn)]);title('Input Data');

subplot(5,1,2);

stem(abs(dataInGuardBand));xlim([1 length(dataInGuardBand)]);title('Input Data + GuardBand');

subplot(5,1,3);

stem(abs(dataInGuardBandIfft ));xlim([1 length(dataInGuardBandIfft)]);title('IFFT(Input Data + GuardBand)');

subplot(5,1,4);

stem(abs(dataInGuardBandIfftCP ));xlim([1 length(dataInGuardBandIfftCP)]);title('CP + IFFT(Input Data + GuardBand)');

subplot(5,1,5);

stem(abs(modData));xlim([1 length(modData)]); title('Output Data');