Question: Under what condition(s) does the Home NodeB Gateway (HNB GW) initiate S15 session termination with the Policy and Charging Rules Function (PCRF)?
Option 1: When a new User Equipment (UE) attaches to the network, requiring policy updates.
Option 2: If the HNB GW initiates deregistration for the Home NodeB (HNB) or receives a deregistration request from the HNB.
Option 3: Upon receiving a CC-Answer from the PCRF for an unrelated session.
Option 4: When the PCRF restarts after an S15 Session establishment.
Explanation: The correct answer reflects the conditions under which the HNB GW initiates S15 session termination with the PCRF, involving either the HNB GW's initiation of deregistration for the HNB or its receipt of a deregistration request from the HNB, ensuring efficient management of sessions and resources in telecom networks.