The present document defines the requirements for synchronization on the GSM radio sub-system. (However@ it does not define the synchronization algorithms to be used in the Base Transceiver Station (BTS) and Mobile Station (MS). These are up to the manufacturer to specify.)
ETSI EN 300 912:1999 history
2001ETSI EN 300 912:2001 Digital Cellular Telecommunications System (Phase 2+); Radio Subsystem Synchronization (GSM 05.10 Version 6.6.1 Release 1997)
2000ETSI EN 300 912:2000 Digital Cellular Telecommunications System (Phase 2+); Radio Subsystem Synchronization (GSM 05.10 Version 8.2.0 Release 1999)
1999ETSI EN 300 912:1999 Digital Cellular Telecommunications System (Phase 2+); Radio Subsystem Synchronization (GSM 05.10 Version 6.4.1 Release 1997)
1998ETSI EN 300 912:1998 Digital Cellular Telecommunications System (Phase 2+); Radio Subsystem Synchronization (GSM 05.10 Version 6.3.0 Release 1997)