Question: What triggers the attempt of an outgoing inter-frequency handover when measurement gaps are used in E-UTRAN?
Option 1: Transmission of the RRCConnectionReconfiguration message by the UE to eNB/RN
Option 2: Receipt of the Handover Command message by the UE from the eNB/RN
Option 3: Transmission of the RRCConnectionReconfiguration message by the eNB/RN to UE
Option 4: Detection of a specific measurement gap pattern by the UE
Explanation: The transmission of the RRCConnectionReconfiguration message by the eNB/RN to the UE is what triggers the attempt of an outgoing inter-frequency handover when measurement gaps are used in E-UTRAN, as specified in TS 36.331. This message indicates to the UE that a handover is being attempted and it should prepare for the handover procedure.