Installed Ultrasn0w 1.2.2 on your jailbroken iPhone 4, 3GS ( Baseband)
Now you can installed Ultrasn0w 1.2.2 on your Jailbroken iPhone 4 or iPhone 3GS on iOS 4.3.1.
The update is also recommended to iPhone users who don’t care about unlocking but want to fix the signal bar issue also need to install Ultrasn0w 1.2.2.
Here are the steps on how to find your iPhone’s baseband.
First you need to go to setting
Now select About
Select Modem Firmware
[ Image courtesy 99bits]