Bit Error Rate (BER) BPSK - Bit error probability (Pb) BPSK

Question

adriane duarte 2020-9-29

0
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https://ww2.mathworks.cn/matlabcentral/answers/601702-bit-error-rate-ber-bpsk-bit-error-probability-pb-bpsk

回答： Kundhuru Bhuvaneswar 2022-9-27

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Hello guys

I made a code and plotted the BER curve. Could anyone help me?

I don't know if I plotted the right graph or if I have some wrong information.

Depending on the parameter that I change the graph is very strange.

Could someone give me an idea?

Follow the code below:

clear; close all; clc; tic;
% BPSK
M = 2;                 
% número de bits ou símbolos
N = 100;   
% Gera bits aleatórios ( matriz de variaveis binarias)
Bits_ale = randi([0 M-1],1,N);
% Modulação BPSK 0 -> -1; 1 -> 1
Bits_bpsk = 2 * Bits_ale-1;  
% Gera bits de marca d'água aleatórios
Bit_wat = randi([0 M-1],1,N);
Theta = 180/4; % (pi/4)
for k = 1:N 
    
    if Bit_wat(k)==1
        
        Bit_enviado(k) = Bits_bpsk(k) * exp(1i * Bits_bpsk(k) * Theta);
        
    else
        
        Bit_enviado(k) = Bits_bpsk(k) * exp(-1i * Bits_bpsk(k) * Theta);
    
    end
    
end
%generating noise with zero mean and var. equal to 1.
noise=1/sqrt(2)*(randn(1,N)+1i*randn(1,N)); 
mean(abs(noise.^2)) %test the power of the noise 
SNR=0:9;   %set SNR in dB
snr_lin=10.^(SNR/10); %calculate linear snr from dB SNR.
y=zeros(length(SNR),N);
%multiply sqrt of snr to signal and add noise:
for i=1:length(SNR)
    
    y(i,:)=real(sqrt(snr_lin(i))*Bit_enviado+noise);
    
end
%reciever and ber count
err=zeros(length(SNR),N); 
Err=zeros(10,2); 
for i=1:length(SNR)
   
    for j=1:N
       
        if y(i,j)>=0
           
            y(i,j)=1;
       
        else
            
            y(i,j)=0;
       
        end
        
    end
    
      err(i,:)=abs(y(i,:)- Bits_ale);
      Err(i,:)=size(find(err(i,:)));
end
 %calculating BER
 
ber=zeros(length(SNR),1);
for i=1:length(SNR)
    
    ber(i)=Err(i,2)/N;
    
end
%theoretical BER calculation
theoryBer = 0.5*erfc(sqrt(snr_lin)); 
semilogy(SNR,ber,'b*-','linewidth',1);
grid on;  
hold on;
semilogy(SNR,theoryBer,'r+-','linewidth',1); 
grid on;  
xlabel('Eb/N0'); 
ylabel('BER'); 
legend('Simulation','Theory') ; 
toc;