Question: When updating a user profile, how does the Home Subscriber Server (HSS) handle adding a newly provisioned Public User Identity to an existing implicitly registered Public User Identity set that is in the Registered state?
Option 1: The HSS sends a single command updating the entire set of Public User Identities, including those not associated with the implicitly registered set.
Option 2: The HSS uses a network-initiated de-registration for all Public User Identities before sending an update for the new set composition.
Option 3: The HSS sends a separate command to add the new Public User Identity to the existing set, which then assumes the registration state of the set it is added to.
Option 4: The HSS cannot add a new Public User Identity to an existing implicitly registered set; instead, it must create a new set.
Explanation: This is correct because, according to the procedure outlined for updating user profiles, when adding a newly provisioned or Not Registered Public User Identity to an existing implicitly registered Public User Identity set (in either the Registered or Unregistered state), the HSS uses a separate command for this addition. The added identity then takes on the registration state of the set it joins. This approach ensures that the update is targeted and efficient, without unnecessarily affecting other Public User Identities not part of the implicitly registered set being updated.