帮忙改一下这个仿真程序吧

[mengzaifei]

我编写了一个个差分空时分组码的MATLAB仿真程序，天线是两发一收，主要思路是在发送端先进性差分空时编码，进行差分空时译码，程序出来的应该是信噪比对应的误码率的曲线图，但是结果不对。这是我的毕业设计，由于时间问题，希望大家帮帮忙！在此先谢过了！
function pb=differential(snr_in_dB)
N=1000;
source=randint(1,N);
x_ref=[1/sqrt(2),1/sqrt(2);-1/sqrt(2),1/sqrt(2)];
map_00=[1,0];
map_10=[0,1];
map_01=[0,-1];
map_11=[-1,0];


pole_1=[];pole_2=[];
for i=1:2:N,
pole_1=[pole_1,source(i)];
pole_2=[pole_2,source(i+1)];
end
numofbiterror=0;


for i=1:N/2,
if (pole_1(i)==0)&(pole_2(i)==0)
r1=1;r2=0;
elseif (pole_1(i)==0)&(pole_2(i)==1)
r1=0;r2=-1;
elseif (pole_1(i)==1)&(pole_2(i)==0)
r1=0;r2=1;
else r1=-1;r2=0;
end
sent_signal=[r1,r2]*(x_ref.');
next_sent_signal=[-conj(sent_signal(2)),conj(sent_signal(1))];
next_x_ref=[sent_signal.',next_sent_signal.'];
%瑞利慢衰落信道H参数
H1=randn(1,1)/sqrt(2)+j*randn(1,1)/sqrt(2);
H2=randn(1,1)/sqrt(2)+j*randn(1,1)/sqrt(2);


sig = sqrt(1/(10^(snr_in_dB/10)));
n1=sig * (randn(1,1) + j*randn(1,1));
n2=sig * (randn(1,1) + j*randn(1,1));
n3=sig * (randn(1,1) + j*randn(1,1));
n4=sig * (randn(1,1) + j*randn(1,1));

R1_signal=H1*x_ref(1,1)+H2*x_ref(2,1)+n1;
R2_signal=-H1*x_ref(1,2)+H2*(-x_ref(2,2))+n2;
R3_signal=H1*sent_signal(1)+H2*sent_signal(2)+n3;
R4_signal=-H1*next_sent_signal(1)+H2*(-next_sent_signal(2))+n4;

R1=R3_signal*conj(R1_signal)+conj(R4_signal)*R2_signal;
R2=R3_signal*conj(R2_signal)-conj(R4_signal)*R1_signal;
r=[R1,R2];
s00=sqrt((abs(R1-map_00(1)))^2+(abs(R2-map_00(2)))^2);


s01=sqrt((abs(R1-map_01(1)))^2+(abs(R2-map_01(2)))^2);
s10=sqrt((abs(R1-map_10(1)))^2+(abs(R2-map_10(2)))^2);
s11=sqrt((abs(R1-map_11(1)))^2+(abs(R2-map_11(2)))^2);
%s00=abs(r-map_00);
%s01=abs(r-map_01);
%s10=abs(r-map_10);
%s11=abs(r-map_11);


s_min=min([s00 s01 s10 s11]);%注意最小距离

if(s00==s_min),
decis1=0;decis2=0;
elseif (s01==s_min),
decis1=0;decis2=1;
elseif (s10==s_min),
decis1=1;decis2=0;
else decis1=1;decis2=1;
end

if (decis1~=pole_1(i))
numofbiterror=numofbiterror+1;
end
if (decis2~=pole_2(i))
numofbiterror=numofbiterror+1;
end


end
pb=numofbiterror/N;