In deployment scenarios where 2G/3G/4G accesses are available, SMS over IP is supported as described in TS 23.204
, and the interactions between HSS and UDM are those defined in clauses 5.5.2
For MT-SMS delivery over 5G NAS in deployment scenarios where support for SMS over IP is also required but 2G/3G/4G accesses are not supported, the MAP-C and/or Diameter S6c refence points with the SMS-GMSC and the MAP-J and/or Diameter S6c reference points with the IP-SM-GW are exposed by the UDM. The UDM and the HSS (IMS) need to interact for the registration of the IP-SM-GW address as defined in clause 18.104.22.168
. Clauses 22.214.171.124
define the interworking between the UDM and the HSS (IMS) during delivery failure and alert procedures.
shows the interaction for the registration of the IP-SM-GW address in the UDM and subsequent SMS routing information retrieval.
The IP-SM-GW registers its address in HSS (IMS) via Sh as defined in TS 23.204
. If the EPS-UDR is used, the HSS (IMS) stores the IP-SM-GW address in the EPS-UDR.
The HSS forwards the IP-SM-GW registration to the UDM using a Nudm_UECM_IPSMGWRegistration request. The request includes the address of the IP-SM-GW to be registered in the UDM. If the 5GS-UDR is used, the UDM stores the IP-SM-GW address in the 5GS-UDR.
The UDM confirms the IP-SM-GW registration with a successful Nudm_UECM_IPSMGWRegistration
response. After successful registration of the IP-SM-GW address, the UDM checks whether message waiting data are stored and alerts all SCs using procedures described in TS 23.204
The UDM receives a request for routing information from the SMS-GMSC via MAP or Diameter. If the 5GS-UDR is used, the UDM queries the 5GS-UDR to read the registered SMSF and/or IP-SM-GW, if any. Routing information is provided to SMS-GMSC from IP-SM-GW or UDM.
The options shown are based on the options for MT SMS procedure described in clause 6.4 of TS 23.204
, considering a 5GC only deployment where UDM is present and HLR/HSS serving 2G/3G/4G accesses is not deployed. Steps 4a-4c correspond to 3a-3c; step 4d corresponds to 3d; and steps 4e-4f correspond to 3e-3f, respectively, as shown in Figure 6.4 of TS 23.204
shows the interaction for the deregistration of the IP-SM-GW address in the UDM.
The IP-SM-GW deregisters its address in HSS (IMS) via Sh as defined in TS 23.204
. If the EPS-UDR is used, the HSS (IMS) removes the IP-SM-GW address from the EPS-UDR.
The HSS forwards the IP-SM-GW deregistration request to the UDM using a Nudm_UECM_IPSMGWDeregistration request. If the 5GS-UDR is used, the UDM removes the IP-SM-GW address from the 5GS-UDR.
The UDM confirms the IP-SM-GW deregistration with a successful Nudm_UECM_IPSMGWDeregistration response.
Step 4 - 5.
If the UDM receives a request for routing information from the SMS-GMSC via MAP or Diameter, the UDM checks if there is an IP-SM-GW address registered for the UE. If the 5GS-UDR is used, the UDM queries the 5GS-UDR to read the registered SMSF and/or IP-SM-GW, if any. If an IP-SM-GW address is not present, the UDM follows the MT SMS procedures defined in clause 4.13.3 of TS 23.502
and TS 23.040
shows the interactions for the unsuccessful MT SMS delivery case in a 5GC only deployment requiring SMSoIP.
Step 1 - 7.
The message delivery fails after the IP SM GW has tried all selectable domains, and the IP-SM-GW forwards the received unsuccessful Delivery report to the SMS GMSC, as described in steps 1-16 in clause 6.5a of TS 23.204
The IP-SM-GW sends a Report SM Delivery Status message to the UDM with accurate results from different domains. If the 5GS-UDR is used, the UDM records the corresponding MWD in the 5GS-UDR.
The IP-SM-GW subscribes to the HSS (IMS) for a one-time notification of the UE being reachable again.
The HSS (IMS) records the subscription and subscribes to notification on UE Reachability for SMS over IP event at the UDM, using the Nudm_EE_Subscribe service operation.
Step 11 - 12.
The UDM checks whether UE Reachability has already been subscribed at the registered AMF(s) (i.e. whether URRP-AMF flag is set), querying 5GS-UDR if applicable. If not already subscribed, the UDM subscribes to UE Reachability notification at the AMF(s) using the Namf_EE
If 5GS-UDR is used, the UDM stores the received EE-Subscription from HSS (IMS) in the 5GS-UDR, and if subscription to AMF is performed in this step, the UDM sets the relevant URRP-AMF flag in the 5GS-UDR.
The UDM acknowledges the subscription of the HSS (IMS).
The SMS-GMSC sends a Report SM Delivery Status message to the UDM. The UDM shall ignore the information provided in this report.
shows the interactions when the UE becomes available in a 5GC only deployment requiring SMSoIP.
The steps described below are based on the procedure described in clause 6.5b of TS 23.204
, considering a 5GC only deployment.
At any time after the unsuccessful SM termination procedure, the UE may become available due to registration in IMS (step 2a). After the IMS registration is finished, the procedure continues as described in step 3.
At any time after the unsuccessful SM termination procedure, the UDM can receive a notification from AMF indicating that the UE is reachable again or an AMF registration (step 2b). The UDM checks whether any NF (e.g. the HSS) has subscribed to notification on UE Reachability for SMS over IP events, querying 5GS-UDR if applicable. If the HSS has subscribed to such notification, the UDM notifies the HSS (step 2c). As the IP-SM-GW has subscribed to the event of UE being reachable again as described in clause 126.96.36.199
, the HSS shall notify the IP-SM-GW (step 2d). If the UE is already registered in IMS, the IP-SM-GW shall then send a Ready for SM message to the UDM (step 2e) and the procedure continues as described in step 3. Otherwise, the IP-SM-GW discards the notification message.
The UDM checks the user's MWD. If MWD is not null, the UDM sends an Alert Service Centre message to the SMS IWMSC.
The SMS IWMSC forwards the Alert Service Centre procedure to the SMS SC.
Upon receipt of the Alert Service Centre message, the SMS SC re-attempts to send the stored Short Message.