GSM 2G Architecture

            BSS - Base Station System
            BTS - Base Transceiver Station
            BSC - Base Station Controller
            MS - Mobile Station
            NSS - Network Sub - System
            MSC - Mobile-service Switching Controller
            VLR - Visitor Location Register
            HLR - Home Location Register
            AuC - Authentication Server
            GMSC - Gateway MSC 
            GSM - Global System for Mobile communication