The SMSIP UE has received the Short Message as described in clause 6.11 and sends a Delivery report (SMS-DELIVER-REPORT) to the IP-SM-GW via the S-CSCF.
This procedure describes the delivery of an Instant Message to a registered or an un-registered IMS subscriber. For the unregistered case, the S-CSCF forwards the Instant Message to the IP-SM-GW based on the unregistered iFC of the subscriber.
UE submits an Instant Message, destined to another IM user or CPM user in another IMS domain, using an appropriate SIP method. The UE may request to hide its Public User Identity from the recipient within the Instant Message, as described in OMA-TS-SIMPLE_IM-V1_0 [12] and in OMA-TS-CPM_Conv_Fnct-V1_0 [17]. If the P-CSCF (not shown in the figure) has received an indication from the S-CSCF that MPS for Messaging is enabled for the originating UE in the HSS (see TS 23.228), the P-CSCF sets the Resource-Priority information on the Instant Message to a value appropriate for MPS, sets the transport priority of the outgoing Instant Message and handles the Instant Message with priority.
The IM AS or CPM AS can forward the Instant Message back to the terminating S-CSCF, e.g. the terminating IM user is offline or the CPM user has no terminating interworking user preferences.
In the case of the CPM AS, if terminating interworking user preferences are set, the Instant Message is routed directly to the IP-SM-GW in which case the procedure continues with step 7.
If the user is authorized, the IP-SM-GW performs service-level interworking by converting the Instant Message to Short Message. The IP-SM-GW shall obtain the routeing information for the UE from the HLR/HSS and deliver the message to the UE. If the sender of the Instant Message requests to hide its Public User Identity from the recipient and operator policy allows for this, the IP-SM-GW shall anonymise the identity of the user to the recipient. Otherwise, if operator policy prohibits this, the IP-SM-GW shall return an appropriate error to the user.
The IP-SM-GW obtains the routeing information for the destination UE from the HLR/HSS. The HLR/HSS also returns the indication whether MPS for Messaging is enabled for the UE in the HSS (see TS 23.228), sets the transport priority of the message and handles the message with priority.
The IP-SM-GW sends the Forward Short Message message to the target MSC/SGSN/MME/SMSF. If the Resource-Priority information on the Instant Message is a value appropriate for MPS, the IP-SM-GW sets the transport priority of the outgoing Short Message to a value appropriate for MPS and handles the Short Message with priority.
The SMS-GMSC interrogates the HLR/HSS to retrieve routeing information. Based on the pre-configured IP-SM-GW address for the user, the HLR/HSS forwards the request to the corresponding IP-SM-GW. The SMS GMSC also interrogates the HLR/HSS to check whether MPS for Messaging is enabled for the UE (see TS 23.228). If the MPS for Messaging is set (enabled) for the UE (see TS 23.228), the HLR/HSS sets the transport priority of the message and handles the message with priority.
The HLR/HSS returns the IMSI and the address(es) of the current MSC, SGSN, MME and/or SMSF to the IP-SM-GW for delivery of the SM in CS/PS domain. The HLR/HSS also returns the indication whether MPS for Messaging is set (enabled) for the UE (see TS 23.228), sets the transport priority of the message and handles the message with priority.
The IP-SM-GW creates an MT Correlation ID as per TS 23.040, which associates the Routing Info retrieval with the subsequent Forward Short Message messages(s), and stores this along with the IMSI of the receiving subscriber. The IP-SM-GW returns to the SMS-GMSC the address of itself, along with the MT Correlation ID in the IMSI field, as routeing information. The IP-SM-GW returns the indication whether MPS for Messaging is set (enabled) for the UE in the HLR/HSS (see TS 23.228). If MPS for Messaging is enabled for the UE, the IP-SM-GW sets the transport priority on the message and handles the message with priority.
The SMS-GMSC delivers the Short Message to the IP-SM-GW in the same manner that it delivers the Short Message to an MSC, SGSN, MME or SMSF, including the MT Correlation ID received from the IP-SM-GW, in place of the IMSI. If MPS for Messaging is enabled for the UE in the HLR/HSS (see TS 23.228), the SMS-GMSC sets the transport priority for MPS and handles the Short Message with priority.
If the user is authorized for service-level interworking, the IP-SM-GW converts the Short Message to an Instant Message. It sends the Instant Message using the appropriate SIP method towards the S-CSCF. If the MPS for Messaging indication for the UE is activated, the IP-SM-GW applies an MPS appropriate Resource-Priority information to the SIP message, sets the transport priority of the message and handles the message with priority.
The S-CSCF forwards the Instant Message to the UE.
The mechanism defined in clause 5.3.4.3 of TS 23.401 and clause 4.2.3.3 of TS 23.502 ensures that if the UE needs to be paged, the MME/AMF pages the UE with priority.