Question: In E-UTRAN, when can a network request a UE to report inter-frequency neighbour cell measurements after security activation, relative to the Security Mode Command and Security Mode Complete messages?
Option 1: Only after receiving the Security Mode Complete from the UE
Option 2: Immediately after transmitting the Security Mode Command, but only if the UE was previously in RRC_IDLE
Option 3: During the initial security setup, but not applicable for connection resume from suspended RRC or RRC_INACTIVE
Option 4: Immediately after transmitting the Security Mode Command, regardless of the UE's previous state (RRC_IDLE, RRC_INACTIVE, or resuming from a suspended RRC connection)
Explanation: According to E-UTRAN protocols for mobility and measurement reporting, the network can request inter-frequency neighbour cell measurements immediately after sending the Security Mode Command, before receiving the Security Mode Complete. This applies across different UE states (e.g., from RRC_IDLE, RRC_INACTIVE, or resuming a suspended connection), ensuring timely measurement reporting for efficient network operation and handover decisions.