GAP General Access Profile (DECT) Gb Gigabyte GEO Geostationary Earth Orbit GFC Generic Flow Control (ATM) GII Global Information Infrastructure GIS Geographic Information System GML Generalized Markup Language GMSC Gateway Mobile Switching Centre (GSM) GMSK Gaussian Minimum Shift Keying GOS Grade of Service GOSIP Government Open System Interconnect Profile GPRS General Packet Radio Service (GSM) GPS Global Positioning System GRAN Generic Radio Access Network (UMTS) GS Global Server GSM Global System for Mobile communications (orig. Group Spéciale Mobile) GSM-R GSM for Railways GTL Globalstar Telecommunications Limited GUI Graphical User Interface