bpsk_ber1.m

this is simulation program for baseband bpsk modem

clear
N = 10^5 % number of bits or symbols

% Transmitter
ip = rand(1,N)>0.5; % generating 0,1 with equal probability
s = 2*ip-1; % BPSK modulation 0 -> -1; 1 -> 1 

t=1000;
b=(12/t)^0.5;
for j=1:N
        u=rand(1,t);
        K=sum(u-0.5);
        n(j)=b*K;% n:gnoise signal
end

Eb_N0_dB = [-3:10]; % multiple Eb/N0 values

for ii = 1:length(Eb_N0_dB)
   % Noise addition
   y = s + 10^(-(Eb_N0_dB(ii)+3)/20)*n; % additive white gaussian noise
   
   % receiver - hard decision decoding
   y1=y>0; 
   
   % counting the errors
   e=xor(y1,ip);
   nErr(ii)=sum(e);
end

simBer = nErr/N; % simulated ber
theoryBer = 0.5*erfc(sqrt(10.^(Eb_N0_dB/10))); % theoretical ber

% plot
close all
figure
semilogy(Eb_N0_dB,theoryBer,'b.-');
hold on
semilogy(Eb_N0_dB,simBer,'mx-');
axis([-3 10 10^-5 0.5])
grid on
legend('theory', 'simulation');
xlabel('Eb/No, dB');
ylabel('Bit Error Rate');
title('Bit error rate curve for BPSK modulation');