Despite speculation that Apple would not be using 4G chips in iPhone 5 after the company's Chief Operating Officer, Tim Cook, said "The first generation of LTE chipsets forced a lot of design compromises with the handset, and some of those we are just not willing to make", 4G LTE test code has been uncovered in recent beta builds of iOS 5.

LTE (Long Term Evolution) is a wireless standard that promises to be up to 10 time faster the current 3G network being used in iPhones. It is often marketed as 4G, although early versions don't fully comply with 4G requirements.

Last week 4G LTE equipment was reportedly seen in a US Apple Store, and Boy Genius Report suggested that Apple is testing 4G LTE iPhones. This rumour was based on code reportedly found in an internal iOS test build that was sent to "one of Apple's major carrier partners." The code, a property list file (.plist) for LTE, has now been found recent beta builds of iOS 5 (the new mobile operating system that is expected to arrive this autumn) that was issued to developers.

MacRumours reports that they have discovered the same LTE.plist file "in at least the last couple of developer builds of iOS 5"

It is still unlikely that 4G LTE chips will be used in the next generation iPhone, after it was deemed too big and costly by analysts. The more likely appearance of LTE will be next year, possibly in the next generation iPad or the iPhone 6, when the second generation of the LTE solution is set to arrive.

In the US, Verizon has already announced plans to convert its networks to LTE, and the UK O2 has announced that it is beginning roll out of LTE, although it is unlikely that 4G will reach the whole of the UK until 2013.