I don't think the interviewer will expect you to work out a complicated problems within short time. Instead, they may want to check your basic understanding on the field. I ever got some questions in digital communications and info. theory, just some concept things like
channel model
what is circular symmetric complex Gaussian random variable and how do we use it in wireless comm., what is Rayleigh/Rice channel, what is match filter, what is Shannon formula and under what condition it is derived, etc.
These should be common sense if you have experience in the field. If you have project experience on wireless comm., make sure you are able to answer any questions regarding the project cuz that's your work.
But don't push yourself too hard, like vancouvernick said, just relax since you've had mcgill as a backup. good luck.