Notes

clear ; %Clear all variables
close all; %Close all figures
num_bit=1e6;
EbNodB=0:1:10;
EbNo=10.^(EbNodB/10);
for n=1:length(EbNodB)
si=2*(round(rand(1,num_bit))-0.5); %In-phase symbol generation
sq=2*(round(rand(1,num_bit))-0.5); %Quadrature symbol generation
s=si+1j*sq; %Adding the two parallel symbol streams
w=(1/sqrt(2*EbNo(n)))*(randn(1,num_bit)+1j*randn(1,num_bit)); %Random
noise generation
r=s+w; %Received signal
si_=sign(real(r)); %In-phase demodulation
sq_=sign(imag(r)); %Quadrature demodulation
ber1=(num_bit-sum(si==si_))/num_bit; %In-phase BER calculation
ber2=(num_bit-sum(sq==sq_))/num_bit; %Quadrature BER calculation
sim_BER(n)=mean([ber1 ber2]); %Overall BER
end
the_Ber = 0.5*erfc(sqrt(10.^(EbNodB/10))); % theoretical calculation of BER
semilogy(EbNodB, sim_BER,'
-
'); %Plotting simulated values
hold on
semilogy(EbNodB,the_Ber,'ko'); %Plotting theoretical values
title('BER curve for QPSK modulation');
legend('Simulation','Theoretical');
xlabel('EbNo(dB)')
ylabel('BER')
grid on