A comparison of mobile phone standards can be done in many ways. Global System for Mobile Communications (GSM, around 8085% market share) and IS-95 (around 1015% market share) were the two most prevalent 2G mobile communication technologies in 2007. In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WIMAX and LTE use OFDM. Time-division multiple access (TDMA) provides multiuser access by chopping up the channel into sequential time slices. Each user of the channel takes turns to transmit and receive signals. In reality, only one person is actually using the channel at a specific moment. This is analogous to time-sharing on a large computer server.
Verizon uses CDMA.
Yes. T-Moblie wants you to bring your own phone if you can't bear to part with...
I think tmobile is gsm.