CNET

Apple has put out a supplemental update to iOS 6.1 for iPhone 4S owners following issues with cellular performance.

iOS 6.1.1, which was released to developers last Wednesday, went out to iPhone 4S owners as a free update this afternoon. In the release notes, Apple says the update "fixes an issue that could impact cellular performance and reliability for iPhone 4S."

The update did not go out to owners on other iOS devices, including newer versions of the iPhone, or cellular-enabled models of the iPad.

Apple's release of iOS 6.1 near the end of January brought 4G LTE support for more carriers on Apple's newest devices, along with a feature that lets users purchase movie tickets from Fandango after finding showtimes using Siri. Apple also returned the option for iTunes Match subscribers to download individual songs from iCloud.

Other changes included new boarding pass behavior in Apple's Passbook software, tweaks to Safari, reworked music playback controls from the lock screen, and a back-end change in Apple's mapping software.

Despite a quick uptake by iOS users, iOS 6.1 has been the cause of headaches for some companies, including phone carrier Vodafone. Last week the company sent a message to its subscribers, urging them not to update to Apple's latest because of "difficulty in connecting to the network to make or receive calls or texts or to connect to the Internet."

Along with the Vodafone message, there were also some logging issues discovered between Apple's Mail app and Microsoft Exchange, forcing some corporate IT departments to outright block iOS 6.1 devices from accessing company e-mail.