Is this even possible? If not I'm really surprised this hasn't been open thru the API yet.
Apple doesn't allow the use of low level network/wifi/cellular api's. Interestinlgy during a previous period, there were apps in the app store that made use of private apis (a few WIFI-Scanners for example). They've all been banded from the appStore by now, as far as I know at least.
Also the newly available (since iOS 4) core telephony framework doesn't offer any methods or properties to serve you the information you're looking for.
So unless you're building a non-app-store-app I don't see a legitimate solution to your problem.
*sam
Several apps in the app store use OS 3 and get signal strength.
Apple fully approves them.
来源：https://stackoverflow.com/questions/3279163/reading-iphone-carriers-signal-strength