Question: What action does an SGSN take when a UE's Closed Subscriber Group (CSG) membership expires for a UE in PMM-CONNECTED State with ongoing emergency bearer services, connected via a CSG cell?
Option 1: Send an Iu message to the RAN indicating CSG membership expiration and initiate handover to another cell.
Option 2: Deactivate all PDP connections (both emergency and non-emergency) immediately.
Option 3: Initiate deactivation of all non-emergency PDP connections without sending a CSG expiration indication to the RAN.
Option 4: Release the Iu connection with an appropriate cause after a configurable time without further action.
Explanation: When a UE's CSG membership expires and there are ongoing emergency bearer services, the SGSN prioritizes maintaining emergency services. Thus, it does not send an indication of CSG membership expiration to the RAN (to avoid disrupting emergency services) but instead initiates deactivation of all non-emergency PDP connections to enforce the changed CSG status. This approach balances compliance with CSG rules and preservation of critical emergency services.