S1AP provides the signalling service between E-UTRAN and the evolved packet core (EPC) and has following functions:
- E-RAB management function
- Initial Context Transfer function
- UE Capability Info Indication function
- Mobility Functions
- S1 interface management functions
- NAS Signalling transport function
- S1 UE context Release function
- UE Context Modification function
- Status Transfer
- Trace function
- Location Reporting
- S1 CDMA2000 Tunneling function
- Warning message transmission function
- RAN Information Management (RIM) function
- Configuration Transfer function
Protocol specification
3GPP TS 36.413 - Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP)