What is UMTS explain its architecture?

UMTS system uses the same core network as the GPRS and uses entirely new radio interface . The new radio network in UMTS is called UTRAN (UMTS Terrestrial Radio Access Network) and is connected to the core network (CN) of GPRS via Iu interface.

There are three major parts to a 3G mobile network:

The infrastructure of 2G and 3G cellular networks are similar. They comprise an air interface between the user’s mobile device and the base station and two core networks; one for circuit-switched voice and another for packet-switched data .