function y = decodpac(rev, H)
% transfer the complex channel matrix into a
% real one for sphere decoding
% Only for QPSK
% rev: received signal vector
% H: channel matrix

codebook=[-1 1];
Radius = 300;

[m, n]=size(rev);
[m1,n1]=size(H);

H=transpose(H);
HT = [real(H) -imag(H); imag(H) real(H)];

rev = transpose(rev); 
for ii=1:m
     Y = [real(rev(:,ii)); imag(rev(:,ii))];
     tt = spheredecod3(Y, Radius, HT, codebook);
     y(:, ii) = tt(1:m1) + j*tt(m1+1:2*m1);
end

y = transpose(y);