Apple Has Released iOS 6.1.1 for the iPhone 4S Only
Apple today released iOS 6.1.1 for iPhone 4S users only. This follows reports that a bug in the iOS 6.1 firmware was affecting 3G performance for numerous customers.
According to the release notes, "This update fixes an issue that could impact cellular performance and reliability for iPhone 4S."
You can get the update from Software Update on your device or download the ipsw directly from here.