Question: What triggers the attempt of an outgoing inter-frequency handover when measurement gaps are not used in E-UTRAN?
Option 1: Transmission of the RRCConnectionReconfiguration message by the eNB/RN to UE
Option 2: Receipt of the HandoverRequest message by the target eNB
Option 3: Detection of a specific threshold for the signal strength of the target cell
Option 4: Expiration of a timer set for handover preparation
Explanation: The transmission of the RRCConnectionReconfiguration message by the eNB/RN to UE is what triggers the attempt of an outgoing inter-frequency handover when measurement gaps are not used in E-UTRAN, as specified in TS 36.331. This message indicates to the UE that it should perform a handover to a different frequency.