vers from one network to another enhanced location services, i.e. new multimedia applications will be possible with the higher rate transmissions (e.g. real time video displays, dynamic broadcasting and easy banking). When comparing to GSM, e.g. in practice the new evolved NEs will then be capable of: providing multiple service components in one stream to a single user terminal si- multaneously for multimedia, thus offering transparency for video communications offering high bit rates for both circuit- and packet-switched bearer services offering multiple connections concurrently to single user MS to serve speech + packet data for example. In addition, during the transition to full IP CN e.g. only the CS part will be able to sup- port services requiring constant bit rate with small delay variations through the proto- col/rate adaptation conversion carried out by the ATM unit. Thus, the 3G NEs will sup- port 642 to 384 kbps transparent or real-time CS data services easily. 3.2.5 Packet Switched (PS) Network Elements (NE) 3.2.5.1 3G Serving GPRS Support Node (3G SGSN) As illustrated in Figure 3.4b, for UMTS R99 the SGSN will require an evolution to 3G SGSN to successfully support 3G PS services. This evolution becomes imperative to acts as a link between the 3G Radio Access Network (RAN) and the packet core, in order to perform both control and traffic handling (gateway) functions for the PS do- main part of the 3G system. An evolved SGSN or a 3G SGSN will then provide: an interface between the Radio Network Controller (Iu) and the 3G Core Network (Gn, Gp). The physical Iu interface will generally use an ATM STM-1 optical in- terface, while the Gn and Gp physical interfaces can use Ethernet or ATM technol- SS7 network interface to communicate with the HLR (Gr), EIR (Gf) and the SMSC (Gd). Some may use X.25 or IP to connect the SMSC. The physical SS7 interfaces for Gf, Gr and Gd will generally use E1-PCM or T1-PCM connections. interface with the charging gateway through the Ga interface. Other functions of the 3G-SG