Two basic technologies in mobile phones, CDMA and GSM represent a gap you can't cross. They're the reason you can't use AT&T phones on Verizon's network and ...
CDMA vs. GSM: What's the Difference?
Differences between GSM and CDMA
What is CDMA Technology
Lecture - 39 GSM and CDMA (Contd.)
Lecture - 38 GSM and CDMA
GSM Vs CDMA: Whats the diffrence?
Стандарт сотовой связи CDMA
Wireless Training - 3G Cellular: CDMA