Connecting iphone to macbook pro through wifi

Hi

I would like to share my macbook pro wireless internet connection to my iphone. How do I do this? The reason why I want to do this is this: I had to change my Thomson router to 5 GHz since I had speed issues with 2.4 Ghz. My iphone 4 does not support 5 GHz. Some apps I download for my iphone need a wifi connection due to big download sizes (GPS maps f.ex.)

Thanks