System 3: “Quantization Index Modulation”
Take a quantization function Q(X). Each grid point represents either a 0 or a 1 message of S. The helper data W is then obtained, such that X + W falls on the grid points of a quantization function QM(), thus,
QM(X + W) = S and |W| is minimal
where QM is an M-dimensional
Thus W is the offset to the nearest grid point.
Function G(W,X) = QM(X + W) is d-e shielding.