devices and the mobile stations. network. Packet Control Transmits data from base sta- Unit (PCU) tions in 2.5G GPRS networks SO that data traffic bypasses the mobile switch. WCDMA NodeB translates between Radio network Controls handover of calls to radio frequencies (signals controller other cell sites. It is connected carried over the air) and to other network controllers landline frequencies, and and to radio base stations. vice versa. GPRS gateway Converts Universal Mobile support node Telecommunications Sys- (GGSN) tem (UMTS) data packets to those compatible with GPRS, the Internet, and other data networks, and vice versa. Signaling gate- Transmits data between radio way service network controllers and node (SGSN) network databases, applica- tions, and billing systems. Also communicates with the GPRS gateway. CDMA2000 BTS converts traffic Packet Data Transmits data traf- between radio frequencies Service Node fic between core and and landline signals. (PDSN) applications. Similar functions as GPRS gateway support node (GGSN). Internet Proto- Same functions as radio net- col Base Sta- work controller. tion Controller (IP-BSC) Mobile and Wi-Fi Networks FOURTH-GENERATION ADVANCED MOBILE SER- VICES There are two fourth-generation (4G) protocols: Worldwide Interoperability for Micro- wave Access 2 (WiMAX 2) and Long-Term Evolution Advanced (LTE-Advanced). Both of these protocols support all IP core networks, but access to the network-the air interfaces-is different. Currently, implementations of new WiMAX and LTE pro- tocols do not support the full 4G speeds defined by standards bodies; nevertheless, they are often referred to as 4G services. Carriers that are currently installing LTE and WiMAX 2 are installing slower, pre-4G versions of the standards. Criteria for 4G protocols were set by the International Telecommunications Union-Radiocommunication (ITU-R). 4G protocols are also referred to as IMT- Advanced (international mobile telecommunications). The ITU-R defines the capabili- ties required for protocols to