Speeds are ALWAYS headline speed, for perfect signal and no other users!
So average cell location = 1/5th of speed or less.
just 6 simultaneous users streaming video
Real speed becomes (40/5) / 6 = 1.33Mbps! Not 40Mbps.
now you know why 3G's 21Mbps is poor.
With about 15 users the "code noise" of CDMA of course means that you have 1/30th not 1/15th speed. So everything else being equal, LTE is twice as good (in same spectrum) but only to the extent of getting say 0.5M to 1Mbps instead of 0.2 to 0.5M, or letting the operator connect 20 users instead of 10,
The other "speed" improvements are simply having more spectrum. Which won't apply at 800, 900 or 1800MHz generally, but only at 2600MHz.
5MHz = 21Mbps (same as 3G HSDPA!)
10MHz = 42Mbps
20Mhz = about 100Mbps
But only for perfect signal. Speed at cell edge is typically 1/100th! All for only one user!
see comparisons of performance vs distance and numbers of users.
Yes, LTE is better than 3G. But if Everything Everywhere get an economic number of customers it will be a slightly faster poorer coverage version of 3G that costs more. No SMS and voice to cross subsidize it. SMS on GSM & 3G costs nothing. Voice is about 1/150th of the traffic for same revenue on 3G. Which is why Three makes no money.