err1.m

一个用matlab写的跳频通信系统仿真

function [p]=err1(rho_in_db)

rho=10^(rho_in_db/10);
Eb=rho;                              %energy per bit
if (rho>2),
    alpha=2/rho;
else
    alpha=1;
end;
sgma=sqrt(1/(2*alpha));               %noise standard deviation 
N=10000;
for i=1:N,
    temp=rand;
    if (temp<0.5)
       data(i)=1;
    else 
       data(i)=0;
    end;
end;

for i=1:N,
    if (data(i)==0),
        r1c(i)=sqrt(Eb);
        r1s(i)=0;
        r2c(i)=0;
        r2s(i)=0;
    else
        r1c(i)=0;
        r1s(i)=0;
        r2c(i)=sqrt(Eb);
        r2s(i)=0;
    end;
    if (rand<alpha),                             %接收到的信号叠加了噪声的概率为alpha
        r1c(i)=r1c(i)+gngauss(sgma);
        r1s(i)=r1s(i)+gngauss(sgma);
        r2c(i)=r2c(i)+gngauss(sgma);
        r2s(i)=r1s(i)+gngauss(sgma);
    end;
end;

    num_of_err=0;
    for i=1:N,
        r1=r1c(i)^2+r1s(i)^2;
        r2=r2c(i)^2+r2s(i)^2;
        
        if (r1>r2),
            decis=0;
        else
            decis=1;
        end;
        
        if (decis~=data(i)),
            num_of_err=num_of_err+1;
        end;
    end;
    p=num_of_err/N