How to correct a QAM time delay
If this represents the received signal where $a$ and $b$ are the real and imaginary parts respectively $s(t-\Delta) \approx [a \cos{(2\pi f_o \Delta)}-b \sin{(2 \pi f_o \Delta)}] \phi(t) \sqrt{2} \cos{(2 \pi f_o t)} + [b \cos{(2 \pi f_o \Delta)} + a \sin{(2 \pi f_o \Delta)}] \phi(t) \sqrt{2} \sin{(2 \pi f_o t)}$ 

one can see exactly how the signal has been rotated. Therefore the rotation can be countered by introducing a sine or cosine to counteract the delay.