Hi Ali, As I mentioned I found the required phase shift to correct the constellation by error and trial, which means for example I changed the phase 45 degrees at first and observed the result, then changed it again and maybe again to get the right value for BER. By the way, if the error is around 0.5, it means each of the four symbol groups are in the adjacent quarter to the one they have to be in, and if the error is near 1, the case is as I have depicted in the two images we were discussing. Thought this might help you in error and trial.
Cheers!