If you want to simulate non strong wifi connections for the iOs simulator on Xcode you will need to throttle your bandwitdth.
There is speed limit but it does not provide a true representation of how different problems affecting slow speeds work.
Apple does have a tool that does not come bundled with the XCode tools.
Hardware IO Tools for Xcode – Late July 2012 was the version I downloaded.
Inside the pkg There is a preferences panel that you can install called
Network Link Conditioner
that you can simulate Edge 3g with packet loss along with many other situations.