For MO-SMS without MSISDN, the IP-SM-GW of the originating side fills the RP-OA field with a value that indicates UE is MSISDN-less to satisfy the protocol requirement. If the originating UE does not have MSISDN or the recipient UE is addressed with SIP-URI (i.e., recipient is not addressed with MSISDN) then IP-SM-GW first tries to deliver the SMS directly to the terminating IMS network. If the terminating IMS network does not accept SMS delivery without MSISDN and responds with a permanent error indication, then IP-SM-GW shall abort any further re-attempt and responds back to sender that SMS delivery has failed.
If the terminating IMS network indicates the SMS delivery failed due to temporary reasons (e.g, UE is not reachable) and the response has included the MSISDN-less correlation ID for the recipient then IP-SM-GW forwards both the SM and MSISDN-less correlation ID to the SMSC for storage and for subsequent retries.
For device triggering, the selection of IMS to deliver MT-SMS without MSISDN is defined in TS 23.682
For SMS between IMS UEs without MSISDN, the delivery of MT-SMS to the recipient is based on the identity from the SIP MESSAGE received from the originating IMS network or retrieved using the MSISDN-less correlation ID from the Forward-Short-Message received from SMSC.
This clause describes the additional functionality required for the delivery of MT-SMS toward a UE in IMS without MSISDN.
During UE IMS registration procedure, the serving IP SM GW obtains IMSI of the UE from the S-CSCF and the serving IP-SM-GW address is indicated to HSS as defined in clause 6.1
and HSS stores this IP-SM-GW address. IP SM GW subscribes to event registration package to receive UE's IMPU (i.e. SIP URI). UE which does not have MSISDN will have at least one SIP-URI as IMPU. When IP-SM-GW receives SM from SMSC with IMSI as the recipient address (i.e. device triggering as defined in TS 23.682
), IP SM GW shall try to deliver the MT-SMS via IMS without retrying to other domain.
When IP-SM-GW receives a SM from originating IMS network via SIP MESSAGE and IP-SM-GW failed to deliver the SM to the recipient and future retry is allowed and possible, then IP-SM-GW shall return a MSISDN-less correlation ID along with an indication of temporary error pointing to unsuccessful delivery attempt to the originating IMS network. This MSISDN-less Correlation ID includes sender's SIP URI, recipient's SIP URI, and HLR-Id which identifies receiver's HLR.