How can I pass the OFDM signal through a Rayleigh channel based on this example?

Example:

QPSK and OFDM with MATLAB System Objects

Command window code:

openExample('comm/QPSKandOFDMwithSysObjectsExample')

This example passes the modulated OFDM signal through a AWGN channel.But how can I pass this OFDM signal through a Rayleigh channel?

I tried to modify the code in the example like this but failed:

1. Set the Rayleigh channel object:

rayChan = comm.RayleighChannel('SampleRate',1e3,'MaximumDopplerShift',0);

2. Add a line of code in the while loop:

txSig = step(rayChan, txSig);

after this line:

txSig = step(hOFDMmod,qpskTx);

The changed while loop is like this:

while errorStats(2) <= maxBitErrors && errorStats(3) <= maxNumBits
    dataIn = randi([0,1],frameSize);              % Generate binary data
    qpskTx = step(hQPSKMod,dataIn);               % Apply QPSK modulation
    txSig = step(hOFDMmod,qpskTx);                % Apply OFDM modulation

    txSig = step(rayChan, txSig);                 % I added

    powerDB = 10*log10(var(txSig));               % Calculate Tx signal power
    noiseVar = 10.^(0.1*(powerDB-snr));           % Calculate the noise variance
    rxSig = step(hChan,txSig,noiseVar);           % Pass the signal through a noisy channel
    qpskRx = step(hOFDMdemod,rxSig);              % Apply OFDM demodulation
    dataOut = step(hQPSKDemod,qpskRx);            % Apply QPSK demodulation
    errorStats = step(hError,dataIn,dataOut,0);   % Collect error statistics
end

The simulation result is:

The result is wrong obviously. But why? How should I modify the code to let the OFDM signal pass through Rayleigh channel and get the right results?

[Daniela Ramirez]

Hi, could you solve this problem?

[Yasantha Samarawickrama]

Hi anybody could sort out this issue? Is it because not using any equalization?