%% Constants
FRM=2048;
MaxNumErrs=200;MaxNumBits=1e7;
EbNo_vector=0:10;BER_vector=zeros(size(EbNo_vector));
%% Initializations
Modulator = comm.QPSKModulator('BitInput',true);
AWGN = comm.AWGNChannel;
DeModulator = comm.QPSKDemodulator('BitOutput',true);
BitError = comm.ErrorRate;
%% Outer Loop computing Bit-error rate as a function of EbNo
for EbNo = EbNo_vector
snr = EbNo + 10*log10(2);
AWGN.EbNo=snr;
numErrs = 0; numBits = 0;results=zeros(3,1);
%% Inner loop modeling transmitter, channel model and receiver for each EbNo
while ((numErrs < MaxNumErrs) && (numBits < MaxNumBits))
% Transmitter
u = randi([0 1], FRM,1); % Generate random bits
mod_sig = step(Modulator, u); % QPSK Modulator
% Channel
rx_sig = step(AWGN, mod_sig); % AWGN channel
% Receiver
y = step(DeModulator, rx_sig); % QPSK Demodulator
results = step(BitError, u, y); % Update BER
numErrs = results(2);
numBits = results(3);
end
% Compute BER
ber = results(1); bits= results(3);
%% Clean up & collect results
reset(BitError);
BER_vector(EbNo+1)=ber;
end
%% Visualize results
EbNoLin = 10.^(EbNo_vector/10);
theoretical_results = 0.5*erfc(sqrt(EbNoLin));
semilogy(EbNo_vector, BER_vector)
grid;title('BER vs. EbNo - QPSK modulation');
xlabel('Eb/No (dB)');ylabel('BER');hold;
semilogy(EbNo_vector,theoretical_results,'dr');hold;
legend('Simulation','Theoretical');
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