@aristotle:
From everything that I have read I thought LTE was using OFDM not WCDMA due to the better use of spectrum.
You are correct.
LTE does NOT use WCDMA for the air interface. LTE uses OFDM for its downlink.
And the LTE backend being all IP would be totally new to AT&T.
In other words, it's yet another new network coexisting with the original GSM towers, just as UMTS 3G does.
My delay in response is because Aristotle (and jav6454) are so confused with their misreading of UMTS and LTE articles, that it's taking me a while to come up with a clear enough explanation so they can understand how they got misled by certain phrases concerning the word "UMTS" and marketing speak such as "evolution".
It's as if someone read that a Hybrid car would be an "evolution" of the current model, and they jumped to the conclusion that their old car secretly had a big electric motor, just waiting to be turned on.
Oddly, all they have to do is think for one second about what they're claiming (that ATT can upgrade to LTE via software), and they'd realize that it doesn't make sense. If such magic were possible, why not do it now?