3G Resuing the previous tecs

What Are Being Reused From Previous Technologies :
Unlike IEEE 802.11 (common names Wi-Fi or WLAN networks), 3G networks are wide area cellular telephone networks which evolved to incorporate high-speed internet access and video telephony. IEEE 802.11 networks are short range, high-bandwidth networks primarily developed for data.
When converting a GSM network to a UMTS network, the first new technology is General Packet Radio Service (GPRS). It is the trigger to 3G services. The network connection is always on, so the subscriber is online all the time. From the operator's point of view, it is important that GPRS investments are re-used when going to Universal Mobile Telecommunications System. Also capitalizing on GPRS business experience is very important.
From Global Pocket Radio Service (GPRS) to Universal Mobile Telecommunications System (UMTS):
-Home location register (HLR) -Visitor location register (VLR) -Equipment identity register (EIR)
From GPRS network, the following network elements can be reused:
-Mobile switching centre (MSC) (vendor dependent) -Authentication centre (AUC) -Serving GPRS Support Node (SGSN) (vendor dependent) -Gateway GPRS Support Node (GGSN)
From Global Service for Mobile (GSM) communication radio network, the following elements cannot be reused
-Base station controller (BSC) -Base transceiver station (BTS)

They can remain in the network and be used in dual network operation where 2G and 3G networks co-exist while network migration and new 3G terminals become available for use in the network.
3G(3rd Generation) Refers to the current generation of data transmission capabilities over a cellular network that provide Internet access and real-time video via smart cellphones.The major 3G technologies are EV-DO, WCDMA, HSPA, GPRS and EDGE, although GPRS and EDGE are often called 2.5G because of their lower speeds.