%TCH/FS信道的外編碼解碼
function [d,tag]=T_FS_EX_DE(u)
%%%%%%%%%%%%%%%%%%%%%%
%反重排和去尾比特
temp=zeros(1,53);
for k=1:25
    temp(2*k-1)=u(k);
    temp(2*k)=u(186-k);
end
temp(51:53)=ones(1,3);
temp(54:56)=u(92:94);

d=zeros(1,260);
for k=0:90
    d(2*k+1)=u(k+1);
    d(2*k+2)=u(185-k);
end
d(183:260)=u(190:267);

before=[0,0,0];
after=[0,0,0];
for i=1:56   %循環計算奇偶校驗位
   after(1)=mod(temp(i)+before(3),2);
   after(2)=mod(before(1)+before(3),2);
   after(3)=before(2);
   before=after;
end

p1=after;
if(p1==0)  %如果譯碼所得奇偶校驗為0，說明未檢查出錯
   tag=0;  %無錯誤
else
   tag=1;  %有錯誤
end