function s=randsn1(K)
Tb=5;   % 1/Tb is baud rate
 r=rand(1,ceil(K/Tb));
 for i=1:ceil(K/Tb)
    if r(i)>=0.5
       sb(i)=1;
    else
       sb(i)=-1;
    end
 end

for i=1:ceil(K/Tb)
   for n=1:Tb
      s(Tb*(i-1)+n)=sb(i);
   end
end