Section: 4.13.3.9 Unsuccessful Mobile terminating SMS delivery re-attempt
Content: The procedure of Unsuccessful Mobile terminating SMS delivery re-attempt is defined as follows: - For SMS delivery, the SMSF and the UDM support the SMSF and UDM role as specified in TS 23.040[ Technical realization of the Short Message Service (SMS) ]  [7]. - If the UE is registered over both 3GPP access and non-3GPP access in the same AMF (i.e. the UE is registered in the same PLMN for both Access Types): - if the MT-SMS delivery over one Access Type has failed, the AMF, based on operator local policy, may re-attempt the MT-SMS delivery over the other Access Type before indicating failure to SMSF; - if the MT-SMS delivery on both Access Types has failed, the AMF shall inform the SMSF immediately. - If the AMF informs the SMSF that it cannot deliver the MT-SMS to the UE (including the cases that UE applies power saving enhancement as described in step 4 of clause 4.13.3.6), the SMSF sends a failure report to the first SMS-GMSC (which can be co-located with IP-SM-GW or SMS Router) as defined in TS 23.040[ Technical realization of the Short Message Service (SMS) ]  [7] or TS 23.540[ 5G System: Technical realization of Service Based Short Message Service; Stage 2 ]  [84]. If the SMS-GMSC has more than one entity for SMS transport towards the UE, then upon receiving MT-SMS failure report, the SMS-GMSC, based on operator local policy, may re-attempt the MT-SMS delivery via the other entity. - After the first SMS-GMSC informs the UDM/HSS that the UE is not able to receive MT-SMS, the UDM shall set the URRP-AMF flag and store the SC address in the MWD list as defined in TS 23.040[ Technical realization of the Short Message Service (SMS) ]  [7] or TS 23.540[ 5G System: Technical realization of Service Based Short Message Service; Stage 2 ]  [84]. - If the UE is registered in an AMF and the UDM has not subscribed to UE Reachability Notification in the AMF yet, the UDM immediately initiates a subscription procedure as specified in clause 4.2.5.2. - When the AMF detects UE activities, it notifies UDM with UE Activity Notification as described in clause 4.2.5.3. If the UE is registered in an SMSF, the UDM clears its URRP-AMF flag and the UDM/HSS clears the MWD list and alerts related SCs to retry MT-SMS delivery. Otherwise, if the UE is not registered in an SMSF, the UDM clears its URRP-AMF flag but the UDM/HSS keeps the MWD list to notify the SC upon subsequent SMSF registration for the UE. - When the SMS-GMSC requests routing information from UDM/HSS for a UE not registered in 5GC, or for a registered UE which has not been yet registered for SMS service, the UDM/HSS responds to the SMS-GMSC that the UE is absent, stores the SC address in the MWD list (if not yet stored) and indicates that to the SC as defined in TS 23.040[ Technical realization of the Short Message Service (SMS) ]  [7] or TS 23.540[ 5G System: Technical realization of Service Based Short Message Service; Stage 2 ]  [84]. When the UDM receives an Nudm_UECM_Registration Request from an SMSF for a UE for which the MWD list is stored and no URRP-AMF flag is set, the UDM/HSS alerts the related SCs to retry the MT-SMS delivery and clears the MWD list. NOTE: This scenario assumes that the UE is not in 2G/3G/4G coverage.