There are two brackets in which we can cover the 3g network one is driven by 3GPP (GSM based) and another is 3GPP2 (CDMA based) these are
UMTS - Its an extension of GSM network and later version are called HSPA and HSPA+ which require a change only on access network without much change in core.
CDMA2000 - Its an extension of CDMA network which provides 3G speeds to CDMA networks. There are two types of major extension of it these are the voice-plus-data 1xEV-DV and the data-only 1xEV-DO.
