Content for  TS 23.272  Word version:  17.0.0

The combined EPS/IMSI attach procedure as described in clause 5.2 has been performed, and extended Idle mode DRX has been negotiated.

The SC initiates transfer of mobile terminating SMS. The HLR is requested for routing number for SMS services and the SMS message is forwarded to the MSC/VLR where the MS/UE is CS attached. The SMS-GMSC may include in case of Deployment Option 2 the Maximum Retransmission Time in the Forward Short Message to indicate that it is capable to retransmit the Short Message until a maximum retransmission time.

The MSC/VLR sends a Paging (IMSI, VLR TMSI, Location Information, SMS indicator, in Deployment Option 2, SM Delivery Timer, SM Delivery Start Time) message to the MME. For Deployment Option 2, if the Forward Short Message received from the SMS-GMSC includes the Maximum Retransmission Time IE, the VLR should forward the received Maximum Retransmission Time IE in the Paging message to indicate to the MME that the SMS GMSC is capable to retransmit the Short Message until the indicated maximum retransmission time. In Deployment Option 2, if the Forward Short Message received from the SMS-GMSC includes the SM Delivery Timer and SM Delivery Start Time IEs, the VLR may include these IEs in the Paging message to indicate to the MME the time until which the VLR supports buffering the Short Message.

If the UE is considered unreachable for paging (as specified in TS 23.682), the MME sends UE unreachable message (cause that indicates UE Temporarily Unreachable and for Deployment Option 2 Requested Retransmission Time, SM Buffer Request Indicator) to the MSC/VLR. For UEs using extended idle mode DRX, the MME proceeds with step 6a, steps 6b-14 as shown in Figure 8.2.4a.2-1 and described below are performed. For UEs in Power Saving Mode, the MME proceeds with step 6a, steps 7a-9, and steps 11-14 as shown in Figure 8.2.4a.2-1 and described below are performed. For Deployment Option 2, if the UE is using a power saving mechanism such as extended idle mode DRX or Power Saving Mode and the Paging message includes the Maximum Retransmission Time IEs, the MME may return an UE Unreachable message to that VLR with the cause UE Temporarily Unreachable and with the Requested Retransmission Time IE requesting the SMS GMSC to retransmit the Short Message at a later time prior to the Maximum Retransmission Time. In that case, the MME shall set the NEAF, so as to notify the VLR of any subsequent UE activity prior to the requested SM retransmission time. In Deployment Option 2, if the UE is using extended idle mode DRX or PSM and the Paging message includes the SM Delivery Timer and SM Delivery Start Time IEs, and if the UE is expected to respond to paging after the paging guard timer but before the time indicated by the SM-Delivery-Timer and SM-Delivery-Start-Time IEs, the MME should page the UE and return an UE Unreachable message to that VLR with cause UE Temporarily Unreachable and with the SM Buffer Request Indicator to request the VLR to buffer the Short Message. In Deployment Option 2, if the VLR included the SM-Delivery-Timer and SM-Delivery-Start-Time IEs in the Paging message, and if the UE Unreachable message indicates a request to buffer the Short Message in the VLR, the VLR shall buffer the Short Message until the time indicated in the Paging message or until receipt of any earlier SGs Service Request message. Steps 7a-9 and 12-14 are not performed. Otherwise, if the UE is considered reachable for paging, steps 6-16 of clause 8.2.4 are performed.

The MME sends the paging request just before the occurrence of next paging occasion. This step is not performed for UEs in PSM.

The MSC/VLR sends a failure report to the SMSC-GMSC with an Absent Subscriber indication as defined in TS 23.040. For Deployment Option 2, if the UE Unreachable message includes the Requested Retransmission Time IE, the VLR shall forward the received Requested Retransmission Time IE in the Failure Report to the SMS-GMSC. In that case, the MSC/VLR shall not set the MNRF flag, and steps 8-9 and 12-13 are not performed.

The MSC/VLR shall, in parallel with step 8, set its MNRF and send an SGs interface Alert Request message to the MME, as described in clause 8.2.5c. The MME shall set the NEAF so as to notify the MSC/VLR of any subsequent UE activity.

When the SMS-GMSC receives the absent subscriber indication from MSC/VLR it sends an SM-DeliveryReportStatus with absent subscriber indication to HSS in order to be notified when the UE becomes reachable, according to TS 23.040.

The SMS-GMSC, in parallel with step 8, sends a failure report to the SC, according to TS 23.040.

The MS/UE is paged by the eNodeBs. This step is not performed for UEs in PSM.

The UE sends a Service Request message to the MME. The UE indicates its S-TMSI in the RRC signalling. The MME sends the S1-AP Initial Context Setup Request message to the eNodeB and the eNodeB establishes the Radio Bearers. The network should ensure the UE is connected long enough that it allows the SC to reattempt to deliver the MT SMS message while the UE is still active. If the UE and the MME accept to use Control Plane CIoT EPS Optimisation, then to enable SMS transfer, the Service Request procedures defined in TS 23.401 are not used, but instead UE and MME shall use Control Plane CIoT EPS Optimisation procedure defined in TS 23.401. For UEs in PSM, Service Request, or Data Transport in Control Plane CIoT EPS Optimisation or Tracking Area Update, as defined TS 23.401, is performed when the UE wakes up from its power saving state.

The MME sends UE-Activity-Indication (IMSI) to the MSC/VLR. For Deployment Option 2, if the UE is using a power saving mechanism (such as extended idle mode DRX or PSM), the MME includes the Maximum UE Availability Time IE in the UE-Activity-Indication message to indicate the time until which the UE is expected to be reachable.

The MSC/VLR sends Ready-For-SM Service to the HLR. For Deployment Option 2, the MSC/VLR includes this information to the HLR if received in step 12.

The HLR initiates Alert-SC function towards the SC as defined in TS 23.040. For Deployment Option 2, the HLR includes the Maximum UE Availability Time IE in the Alert-SC if received at step 12a.

The SC initiates a new attempt to deliver the MT SMS according to clause 8.2.5. For Deployment Option 2, the SC prioritizes the retransmission of pending Mobile Terminated Short Messages to UEs using a power saving mechanism, i.e. UEs known to have a Maximum UE Availability Time.

Steps 1-5 as described in clause 8.2.4 are performed.

If the UE is considered unreachable for paging due to using extended idle mode DRX or PSM (as specified in TS 23.682), the MME sends a Service Request message to the MSC/VLR. If the MME proceeds with step 6a, steps 6b-16 as shown in Figure 8.2.4a.3-1 and described below are performed. Otherwise steps 6-16 of clause 8.2.4 are performed.

The MSC/VLR builds the SMS message to be sent as defined in TS 23.040 (i.e. the SMS message consists of CP DATA/RP DATA/TPDU/SMS DELIVER parts). The MSC/VLR forwards the SMS message to the MME in a Downlink Unitdata message. The MME stores the received SMS message.

The MME sends the paging request just before the occurrence of next paging occasion. This step is not performed for UEs in PSM.

The MS/UE is paged by the eNodeBs. This step is not performed for UEs in PSM.

The UE sends a Service Request message to the MME. The UE indicates its S TMSI in the RRC signalling. The MME sends the S1-AP Initial Context Setup Request message to the eNodeB and the eNodeB establishes the Radio Bearers. If the UE and the MME accept to use Control Plane CIoT EPS Optimisation, then to enable SMS transfer the Service Request procedures defined in TS 23.401 are not used, but instead UE and MME shall use Data Transport in Control Plane CIoT EPS Optimisation procedure defined in TS 23.401. For UEs in PSM, Service Request, or Data Transport in Control Plane CIoT EPS Optimisation or Tracking Area Update, as defined TS 23.401 is performed when the UE wakes up from its power saving state.

The MME encapsulates the SMS message in a NAS message and sends the message to the MS/UE.

Steps 9c-16 as described in clause 8.2.4 are performed.