16 QAM simulation over Rayleigh channel

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Den
Den 2011-10-8
Hello everyone! I would like to demodulate 16 QAM modulated signal after Flat Rayleigh Channel and AWGN by usining modem.qamdemod. My BER graph is far from the thoretical. Any help will be appreciated. Den.
% Create Rayleigh fading channel object.
chan = rayleighchan(1/1000,100);
g = chan.PathGains % Retrieve the PathGains property
%chan.NormalizePathGains=0;
dop_flat = doppler.flat
chan.DopplerSpectrum = dop_flat
chan.StorePathGains = 1;
%chan.StoreHistory = 1; % Allow states to be stored
chan.ResetBeforeFiltering=0;
chan
% Generate data and apply fading channel.
M = 16; % QAM modulation order
k = log2(M);
hMod=comm.RectangularQAMModulator(M); % Create a 16 QAM modulator
%hMod.InputType='bit';
display(hMod)
%hDemod=comm.RectangularQAMDemodulator; % Create a 16 QAM Demodulator
%hDemod.outputtype='bit';
%display(hDemod)
% Initialize scatter plot.
scatterPlot = commscope.ScatterPlot;
scatterPlot.Constellation=16;
tx = randint(1e4,1,M); % Generate a random bit streams
%tx1=dec2binvec(tx,5*1e4);
qamSig = step(hMod, tx); % Modulate16 QAM the signal
%scatterplot(qamSig)
axis([-20 20 -20 20]); % Set axis ranges.
grid on;
%update(scatterPlot,qamSig,'b');
% Compute error rate for different values of EbNo
EBNO = 1:50; % Range of EbNo values, in dB.
numEBNO = length(EBNO);
for n = 1:length(EBNO)
%clear hDemod;
hDemod=comm.RectangularQAMDemodulator; % Create a 16 QAM Demodulator
fadedSig = filter(chan,qamSig); % Apply the channel effects
clear snr;
clear rxSig1;
snr = n + 10*log10(k) - 10*log10(4);
rxSig1= awgn(fadedSig,n,'measured');
eqSig = rxSig1 .* conj(chan.PathGains);
rx = step(hDemod, eqSig); % Demodulate
% Compute error rate.
[nErrors, BER(n)] = biterr(tx,rx);
BER
% Plot the new data
update(scatterPlot,eqSig,'r');
end;
% Compute theoretical performance results, for comparison.
BERtheory =berfading(EBNO,'qam',M,1)
% Plot BER results.
semilogy(EBNO,BERtheory,'b-',EBNO,BER,'r*-');
legend('Theoretical BER','Simulation BER');
xlabel('EbNo (dB)'); ylabel('BER');
title('16 QAM over Rayleigh Channel');
grid on;
end

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