UMTS Core Network Evolution

The core network architecture for 3GPP Release 1999 is not greatly different
than the core network architecture of GSM/GPRS. Clearly, the core network
must be upgraded to support the new interfaces to the radio access
network, but a completely new architecture is not needed. In 3GPP
Release 4 and 3GPP Release 5, however, we find significant enhancements
to the core network.