I.1 General

23.0403GPPRelease 17Technical realization of the Short Message Service (SMS)TS

An EPS network using SMS in MME delivers short message services over EPS NAS signalling.

For the architecture and the definition of reference points for SMS in MME see 3GPP TS 23.272 [45], annex C.

Between the architecture and the reference points for SMS in MME and the architecture and the reference points shown in clause 4.1, figure 5, of the present specification the following mapping can be established:

Table I.1: Mapping between architecture and reference points for SMS in MME and the present specification

	SMS in MME	present specification
	HSS	HLR
Network entities	MME	MSC + VLR
	E-UTRAN	(not shown in figure 5)
	UE	MS
	(not applicable)	MME (NOTE 1)
	S6a	(not shown in figure 5)
	S6c/C	2
Reference points	SGd	3
	(not applicable, MME internal)	4
	Uu + S1-MME	5
	(not applicable)	6
NOTE 1: In figure 5, the MME is only acting as a relay for SMS transfer via the SGs.

For the purpose of supporting SMS in MME, the MME shall implement the requirements specified in the present specification for the MSC and the VLR with the following modifications:

1) "GSM/UMTS system" is to be replaced with "EPS".

2) Throughout the text and in the figures, message names, parameter names and cause values:

"MSC" is to be replaced with "MME";

"VLR" is to be replaced with "MME internal subscriber register";

"HLR" is to be replaced with "HSS/HLR";

"MS" is to be replaced with "UE";

"non GPRS" is to be replaced with "EPS";

"IMSI detached" is to be replaced with "EPS detached".

3) The protocol used on reference point 2 (reference point S6c) is based on Diameter (see 3GPP TS 29.338 [50]).

4) The protocol used on reference point 3 is based on Diameter (see 3GPP TS 29.338 [50]).

5) Reference point 4 is MME internal, and operations performed on this reference point are not standardized. In the message flows of clause 10, the MME replaces the combination of MSC and VLR, and messages exchanged between MSC and VLR are replaced with MME internal communication.

6) The protocol used between HSS and MME (reference point S6a) is based on Diameter (see 3GPP TS 29.272 [46]). In the alert procedure in clause 10.3:

MAP ReadyForSM is to be replaced with Diameter NotifyRequest (ReadyforSM).