iOS 7 autolayout concept using xib

Hi,

I am using Xcode 5 and iOS 7(SDK). Previously i have devleoped the app with Xcode 4.6.2 and iOS 6(SDK) using XIB with autolayout. After upgrading to new version of Xcode and SDK i am unable to change my viewcontroller height which is 20 px above and merged with status bar. I have tried with all scenarios but i am unable to find the solution.Any ideas would be appreciated??