C.2 Architecture

23.2723GPPCircuit Switched (CS) fallback in Evolved Packet System (EPS)Release 17Stage 2TS

As outlined in the architecture figure below SMS in MME requires support of SMS functionality in the MME and the MME also needs to receive SMS subscription information from the HSS. The SMS subscription information may be received through the S6a interface.

Figure C.2-1: SMS in MME Architecture

Figure C.2-2: SMS in MME architecture using IWF

There is no impact on the UE and E-UTRAN. The SMS entities (including SMS router, etc.) functionality to support SMS in MME is the same as defined for reference point 2 and 3 in TS 23.040 [14] except the SGd and S6c interfaces use Diameter protocols as specified in TS 29.338 [43]. The interaction between SMS in MME and SMS over IP is described in TS 23.204 [15].

NOTE 1: The HSS may support both a Diameter S6c and a MAP C interface to SMS entities that have not evolved to S6c, or the SMS entities may support both interfaces to obtain routing information from HSS’s that have not evolved to S6c.

NOTE 2: According to TS 23.040 [14], the SMS-Router is optional and only required for MT SMS.