Question: In E-UTRA, how does a UE in RRC_IDLE mode initially detect changes to System Information after cell selection or reselection?
Option 1: Via periodic broadcast of System Information on the Broadcast Channel (BCH)
Option 2: Through a Paging message or Direct Indication information on MPDCCH/NPDCCH
Option 3: By continuously monitoring the Control Channel (CCH) for updates
Option 4: Upon receipt of a dedicated RRC Connection Reconfiguration message
Explanation: In E-UTRA, UEs in RRC_IDLE mode aren't constantly connected. To notify them of System Information changes efficiently, the network uses Paging messages or Direct Indication on MPDCCH/NPDCCH during allocated Paging Occasions. This allows the UE to become aware of changes and re-acquire updated System Information as needed, balancing power efficiency and staying informed. Options 1 and 3 are incorrect because BCH doesn't specifically indicate changes to idle mode UEs, and continuous CCH monitoring would be inefficient in idle mode.