How to correct a QAM time delay How can you correct the anticlockwise rotation that occurs in the received constellation of a QAM system? 


My only idea is to compensate the delay with an advance but this is impossible since you would have to decode the message before receiving it.
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.