In the Macworld offices in downtown San Francisco we were able to measure download speeds of 20Mbps on AT&T and 23Mbps on Verizon. Upload speeds were 17Mbps (AT&T) and 14MBps (Verizon). Compare this to the 4Mbps downloads and 0.3MBps uploads I saw on AT&T’s older GSM network. Downloads that are five times faster? Not bad.
How’s that stack up to the UK? On the iPhone 5 with the DC-HSDPA network we managed to get a 13MB download connection with regular download speeds between 7 and 10MBs and between 2 and 5 MBPs upload. All on the Three network.
So with a decent connection in the UK you don’t need to cry too much about not having 4G just yet. But speed isn’t the best part of L TE. It won’t be just faster; it will remain faster, in a consistent and reliable fashion, a greater portion of the time than 3G. The iPhone 5can access all of the following kinds of networks:
• EV-DO = 3.1Mbit/s
• HSPA 7.2 = 7.2Mbit/s
• HSPA+ = 21Mbit/s
• DC-HSDPA = 42Mbp/s
• LTE 4G = 73Mbp/s
Where you might have coverage gaps, high congestion with other users in the same mobile cell in a city (or even a small town with few base stations), or a huge variation in speed, it’s likely that L TE will smooth all that out. Carriers will have a much larger pool of bandwidth that the technology lets them to divide it up more precisely among users trying to gain access.
Source : The Complete Guide to the iPhone 5