3. System Architecture

3.1 High‑Level Architecture

The SMS service architecture is primarily a control-plane system built around a Service Centre (SC) that performs store-and-forward message handling [TS 23.040]. In a typical flow, a mobile-originated (MO) SMS is transported from the Mobile Station (MS) to the SC, and a mobile-terminated (MT) SMS is delivered from the SC to the destination MS. The SC (commonly called an SMSC) maintains a message store for holding undelivered messages and uses a forwarding/routing engine to deliver them when the recipient becomes available. 

The network relies on signaling (control-plane protocols) rather than a user-plane bearer to exchange SMS – for example, GSM/UMTS networks use SS7/MAP signaling to route SMS messages between the SMSC and mobile network elements. The high-level architecture thus includes the SC (with its message database and logic), a routing engine to determine the proper delivery path, various protocol adapters to interface with different network protocols, and an OAM layer for administration and maintenance (alarms, logs, etc.).