Question: In a scenario where a UE is in PMM-IDLE state but the 3G-SGSN believes it's in PMM-CONNECTED state, what triggers the recovery of this unsynchronized state?
Option 1: Periodic Location Area Update (LAU) from the UE
Option 2: Successful MS-initiated connection establishment for data transfer or RAU, or a failed downlink transfer with cause 'IMSI unknown in RNC'
Option 3: Automatic handover to a different RNC
Option 4: Receipt of an SMS by the UE, prompting a network-initiated connection setup
Explanation: This unsynchronized state between the UE (PMM-IDLE) and the 3G-SGSN (PMM-CONNECTED) is recovered through specific actions. The correct trigger involves either a successful MS-initiated connection establishment (for RAU or data transfer), realigning the states, or a failed downlink transfer due to 'IMSI unknown in RNC', leading to a paging procedure that corrects the state mismatch, highlighting the importance of state synchronization for seamless communication.