Apple's latest developer builds for iOS 5 contain a snippet of code that mentions LTE, according to enthusiast site MacRumors, prompting speculation that the company may be testing 4G internally.
Peeking into the iOS 5 firmware for a couple of developer builds, MacRumors found a property list (.plist file) that points to LTE, or Long Term Evolution. Uncovered only in builds for the GSM iPhone 4 and CDMA iPad 2, the LTE.plist file was found to be related to an application that Apple uses for field testing.
The apparent discovery follows reports from Boy Genius Report a week ago that found the same LTE property list file in an internal iOS build from one of Apple's carrier partners. That led BGR to conclude that Apple was already testing LTE out in the field.
Offering further breadcrumbs to the 4G rumors, Endgadget last week posted an image reportedly of LTE equipment being installed at an Apple store. Though the image was later removed, Engadget cited an anonymous source who said the equipment was supplied by AT&T.
MacRumors also cites a recent article from Forbes, which says that Apple is on the lookout for more engineers to help it run LTE tests in the field.
Rumor: Carriers testing 4G LTE iPhones
Apple store reportedly getting a 4G LTE hookup
iPhone 5 now rumored to launch October 7
Why the iPhone 5 won't have Verizon 4G (Q&A)
Despite the snippets of code found in iOS 5, 4G LTE is unlikely to surface in the iPhone anytime soon. Assuming the iPhone 5 launches in October, as the latest reports suggest, the new device will clearly be a 3G phone if Apple is just field testing 4G now.
Apple has also been wary of jumping too quickly to 4G due to the technology's current limitations. Announcing Apple's quarterly results this past April, Chief Operating Officer Tim Cook said that the first-generation LTE chipsets "force a lot of design compromises."
In an interview with CNET in April, Will Strauss, president of wireless chip market research firm Forward Concepts, explained that chipsets for LTE phones will need to integrate 3G to cover areas where 4G is not available. And such integrated chipsets are not expected until next year, according to Strauss.
LTE coverage is another limitation. Verizon Wireless recently said that its LTE network is now available to half of the U.S. population. However, AT&T is just starting to ramp up its LTE network, with plans to cover five cities over the next few months and 15 markets by the end of the year.