Design space for Admob Banner

Hello,
The question is really old. I decide to ask because I still have no good solution for both Android and iOS. I'm trying to make a space at the bottom of screen to put Admob banner. I tried many ways. All of them are going to be stucked.
I can get height of banner, but I can't get height of screen. It's not Screen.height, Camera.rect.... Because Admob use actual screen size. Screen.height and other are depend on TargetDPI (at PlayerSettings). They're not actual screen size.
I see many games that developed by Unity3d able to make a nice space to show banner. Do they use a trick? May they make the space is about (15% of screen height)? Someone know a good solution for mobile (android and ios), please guide me. I've took 2-3 years to find a good solution