pproaches, where resources are dedicated to a single application, the MRFP provides media processing as a shared resource to a number of different applications. Media gateway (MGW)-The MGW provides interworking with the PSTN and the Internet. Whereas earlier-generation wireless networks make use of the MGW, newer networks are served by the GGSN for con- nectivity with the Internet. Serving GPRS support node (SGSN)-The SGSN provides packet rout- ing to and from the SGSN service area for all users in that service area. The SGSN provides the packet-switched link to mobile stations. Gateway GPRS support node (GGSN)-The GGSN acts as a gateway between the GPRS network and public data networks such as IP and X.25 networks. GGSNs also connect to other GPRS networks to facilitate GPRS roaming. RAN components-The transport layer is also home to the RAN compo- nents, including the following: - Base transceiver station (BTS)-The BTS handles the radio interface to the mobile station. It is the radio equipment (transceivers and antennas) needed to service each cell in the network. - Base station controller (BSC)-The BSC controls a group of BTSs and provides all the control functions and physical links between the mobile switching center and BTS. Its functions include handover operations, cell configuration data, frequency administration between BTSs and mobile stations, and control of radio frequency power levels in BTSs. Node B-In 3G UMTS networks, the base transceiver station is called Node B. It is differentiated from the base stations in 2G GSM networks by the fact that is uses W-CDMA as the air transport technology. Chapter 16 Emerging Wireless Applications - Radio network controller (RNC)-In 3G UMTS networks, the RNC is in charge of controlling Node Bs. In traditional implementations, Node B has minimum functionality, but with the advent of HSDPA (described in Chapter 14), some logic (such as retransmission) is handled on Node B in order to reduce response times. IMS service delivery platforms enable the enhanced service