Since the release of Apple’s iOS 5.1 operating system a couple of days ago, a strange issue has been affecting users of AT&T that have been met with the iPhone 4S showing a 4G icon, and providing a ridiculous mystery.

According to an article on the Huffington Post after users on the AT&T network downloaded iOS 5.1 to their iPhone 4S, many reported seeing a 4G icon appear next to the cell signal icon in the top left hand corner of the handsets screen. Before users can start celebrating with a sudden boost in data speed, they will obviously be the same as before when the icon was showing 3G.

AT&T does offer a 4G LTE service to some of its customers using compatible hardware, but the iPhone 4S doesn’t feature 4G connectivity to use the network. Instead it uses the HSPA+ network that is an enhanced 3G service, but is slower than LTE but is referred to as 4G by both AT&T and T-Mobile.

Some of the press considers HSPA+ to actually be 3G technology and the sudden appearance of the 4G icon could be some marketing by the carrier. An AT&T spokesman commented on the matter and stressed that the carrier uses two 4G systems, LTE and HSPA+, and the iPhone 4S being an HSPA+ device is why the 4G icon is being shown.

He went on to say the iPhone 4S “has always had that capability, and we’re glad it’s now displayed on the phones”, and added that a number of standards bodies except “HSPA+ is a 4G network”. Back in December 2010 though the International Telecommunications Union found that early speed standards for 4G were a long way from being hit by any network, so WiMax, LTE and other “evolved 3G technologies” that included HSPA+, were allowed to be referred to as 4G.

Other standard bodies don’t agree with this though with many only recognizing WiMax and LTE as true 4G options in the US. Meanwhile owners of the iPhone 4S on AT&T may not have got any faster data speeds since downloading iOS 5.1, at least they got a nice new icon to look at.