It seems the new iOS 5.1 update has caused a certain amount of confusion to iPhone 4S user’s on the AT&T network as people have been seeing their phones are connecting to 4G networks. Now one would think that this is impossible with a mere software update alone and you would be right. A simple software update could not allow any phone to connect to a 4G network when it doesn’t have the right chipset to do so but there is a possible explanation. The phones are most likely connecting to AT&T’s HSPA+ network which many providers label as 4G; however, these networks are based on 3G bands which would explain how the phones can be connected to them.
AT&T’s Mark Siegel has confirmed that the phones are connecting to the HSPA+ network with the following statement. “The iPhone 4S operates on AT&T’s 4G HSPA+ network and as such, it is only appropriate that people see ‘4G’ on the phone when they are connected to HSPA+.”
So hey congratulations to AT&T 4S users, it looks like you may be getting faster speeds. That is if they haven’t been connected to these networks from the beginning.