Issue with Implementing Subscription SMS Feature in OAG

[tranvantai2905]

To implement the subscription SMS feature, I see two possible approaches in OAG, but both come with challenges:

+Approach 1: Subscribe to NEF with MonitoringType: UE_REACHABILITY and ReachabilityType: SMS.

However, according to TS 29.122, The enumeration ReachabilityType represents a reachability type. It shall comply with the provisions defined in Table 5.3.2.4.4-1. If reachabilityType is set to "SMS", the monitoring event request from SCS/AS shall be only for a one-time monitoring request.

+Approach 2: Subscribe to NEF with MonitoringType: UE_REACHABILITY and ReachabilityType: DATA. When NEF notifies that data is unreachable, the camera will trigger a one-time request to NEF to check the SMS status of the UE. However, NEF only notifies when the UE becomes reachable, even though UDM’s report supports the statuses: [ UNREACHABLE, REACHABLE, REGULATORY_ONLY ].

The SCS/AS requests to be notified when the UE becomes reachable for sending either SMS or downlinkdata to the UE.

Given these constraints, what would be the recommended approach to properly implement this feature?