function [X,Xb]=gen_X(M)   
for i=2^(M-1):2^M-1
        base2=dec2base(i,2,M);
        temp=zeros(1,length(base2));
        for j=1:length(base2)
            temp(j)=base2(j)-48;
        end
        X(:,i-2^(M-1)+1)=temp';
end
    clear i j base2 temp;
    Xb=[];
    [row_X,col_X]=size(X);
    for i=1:col_X
        ind_X=find(X(:,i)==1);
        for j=1:2^length(ind_X)
            base2=dec2base(j-1,2,length(ind_X));
            temp=zeros(1,length(base2));
            for jj=1:length(base2)
                temp(jj)=base2(jj)-48;
            end
            ind_temp=find(temp==0);
            temp(ind_temp)=-1;
            X(ind_X,i)=temp';
            Xb=[Xb X(:,i)];
        end
    end