function output=bpsk_mapping(signal_in)
N=length(signal_in);
output=zeros(N,1);

for m=1:N
    if      signal_in(m,:)==[0]
               output(m)=-1;
    elseif  signal_in(m,:)==[1]
               output(m)=1;
    end
end
% scatterplot(output)       %畫星座圖