Low/bad signal on iPhone 4 after upgrading to IOS 6 I recently upgraded my iPhone 4 to IOS 6 (from 5.1.1 it had before), and since then I'm having lots of signal troubles: the signal is always low and unreliable, and the iPhone continuously switches between 3G and GPRS (also draining the battery in the process). Internet access is almost unusable, and sometimes I can't even make or receive calls.

I'm in Italy, my carrier is TIM; however, this is not a carrier problem, and is unrelated to the actual place I'm in: I'm having these signal troubles in the very same places where I had full signal strength before the IOS upgrade.

I've been searching around for a while, and looks like this is quite a common problem; various solutions have been proposed (including downgrading to IOS 5 on the assumption that this is caused by some bug in IOS 6), but no agreement has been reached about how to actually solve it.

How to fix this?
The only solution that actually worked was a full factory reset:


Make a backup of your iPhone using iTunes.
Using iTunes, perform a full reset of the iPhone.
After the iPhone reboots, disconnect it from iTunes and go through the initial setup.
Connect the iPhone back to iTunes.
When asked by iTunes, choose to restore the backup.
If applications are missing after the restore, perform a full sync to have them re-installed.


I also called Apple support, and they confirmed this is a known and common problem when upgrading to IOS 6, and a full reset is the only way to permanently solve it.