無線接口演進Radio Interface Evolution: Contents f GSM & UMTS Evolution: From 2G to 4G 1 GSM & UMTS Evolution In the same way as GSM, UMTS is undergoing a permanent evolutionary process. Step by step different aspects of the system such as services, network architecture and the radio interface are enhanced and additional options are integrated. This process should be continued towards 4G and beyond. Abbreviations used in the following: AMR: Adaptive Multi Rate EDGE: Enhanced Data Rates for the GSM Evolution EFR: Enhanced Full Rate EUDCH: Enhanced Uplink for Dedicated Channels FR: Full Rate GPRS: General Packet Radio Services HR: Half Rate HSCSD: High Speed Circuit Switched Data HSDPA: High Speed DL Packet Access IMS: IP Multimedia Subsystem LCR-TDD: Low Chip Rate Time Division Duplex MBMS: Multimedia……