networks
Ya, AT&T and T-Mo uses GSM for 2G and UMTS (W/CDMA) for 3G. Both are going LTE for 4G.
Verizon uses CDMA for 2G, CDMA2000 1xRTT and 1xEV-DO for 3G, and will be going to LTE for 4G.
Sprint uses CDMA2000 and iDen and has gone WiMax for 4G, but they have ensured that the antennas and most of the equipment they bought can be dual-purposed to LTE.
The fun part is that even if you buy a 4G phone on AT&T or Verizon, even though it could theoretically roam onto either LTE network (asumming the correct radio band), it couldn't fall back to 3G/2G.
Biting the hand that feeds IT
