GSM Originating SMS Call
This scenario describes the session setup for a GSM originating SMS. This sequence diagram describes the SMS signaling and data transfer between the mobile subscriber and the SMS service center. [ SMS is implemented by sending Short message transported via a GSM SDCCH (Standalone Dedicated Control CHannel) signalling channel. Thus they can be received while the user is talking. The MS establishes an SDCCH using RR establishment procedure.
SMS Protocol stack consists of:
- SM Application layer (AL)
- SM Transfer layer (TL):SM-TL transfers SM-AL messages. SM-TL messages are called Transfer Protocol Data units (TPDUs).
- SM Relay layer (RL):SM-RL provides services to transfer TPDUs and corresponding delivery report for the SM-TL. SM-RP is the protocol between peer SM-RL entities at MS and MSC. SM-RP messages are Relay Protocol Data Units (RPDUs).
- SM Connection Management sub-layer (CM-sub). CM-sub layer protocol, Short Message Control Protocol SM-CP provides services to SM-RL and communication between peer Short message Control entities, SMCs.
- SC talks to MSC via TCAP/MAP.