echo on
SNRindB1=0:2:10;
SNRindB2=0:0.2:10;
for i=1:length(SNRindB1),
  % 仿真誤碼率
  smld_err_prb(i)=smldPe59(SNRindB1(i));
end;
% MATLAB script that generates the probability of error versus the signal-to-noise ratio
initial_snr=0;
final_snr=15;
snr_step=1;	
tolerance=1e-7;      %用于積分的容限
minus_inf=-20;       %實際上是無窮大
plus_inf=20;         %實際上是無窮大
snr_in_dB=initial_snr:snr_step:final_snr;
for i=1:length(snr_in_dB),
    snr=exp(snr_in_dB(i)*log(10)/10);
    Pe_4(i)=(2/3)*quad8('bdt_int',minus_inf,plus_inf,tolerance,[],snr,4);
    % 理論誤碼率
    theo_err_prb(i)=Pe_4(i) 
end;
% 隨后為繪圖命令
semilogy(SNRindB1,smld_err_prb,'*');
hold
semilogy(snr_in_dB,theo_err_prb);  
pause
A=[0 0.1 1.0 2.0];
for i=1:4,
    sgma=sqrt(A(i));
n0=sgma*randn(1000,1);
n1=sgma*randn(1000,1);
n2=sgma*randn(1000,1);
n3=sgma*randn(1000,1);
x1=1.+n0;
y1=n1;
x2=n2;
y2=1.+n3;
pause
plot(x1,y1,'o',x2,y2,'*')
axis('square')
end;