are available for the structure and form of the CN in that it may be an evolved mobile network or an evolved fixed network. Most likely, however, the CN will support both real-time and nonreal-time con- nections. This may be achieved through both circuit- and packet-switched technologies, or possibly packet-switched alone. Figure 11-9 shows the proposed 3G CN architecture. One can see that the UTRAN is supporting two connections on the 1u interface linking a 3G-SGSN and an Mobile Switching Center (MSC). The 3G-SGSN is connected to the Public Land Mobile Network (PLMN) backbone network via the Gn interface and, as with GPRS, this connection is based upon Infrared (IR) packet data and leaves the CN through either a 3G-GGSN or Border Gateway, which connects the Internet (Gi) and vis- ited PLMN (GP), respectively. As mentioned earlier, it may be possible to do without the 1-CS interface supporting the MSC with the introduction of Voice over IP (VoIP). This would enable real-time connections to run over a packet-switched technol- ogy, therefore reducing the need for traditional circuit-switched equipment. The Third-Generation Partnership Project (3GPP) is currently investigating Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hil Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Future Enhancements and Services Chapter 11 1,-CS Figure 11-9 The CN in a 3G world. 1,-PS 3G GGSN 3G SGSN I,-PS Router 3G SGSN Internet 3G GGSN the possibility of interworking the VoIP standards (H.323) into their tech- nical specifications. The 3GPP is proposing the introduction of mobile IP into the CN. This would enable a subscriber to register his or her home IP address onto any visited network supporting mobile IP and thus negate the requirement for multiple IP addresses. Such technology would be independent of the under- lying network technology and would enable subscribers to move easily from their LAN to a mobile envi