Question: What triggers an attempt of an outgoing intra-eNB handover from DeNB cell to RN, and what is added to the relevant per handover cause measurement as a result?
Option 1: Transmission of the RRC ConnectionReconfiguration message to UE, and each successful handover is added.
Option 2: Receipt of the S1AP Handover Request message from the MME, and each failed handover is added.
Option 3: Transmission of the RRC ConnectionReconfiguration message to UE, and each RRCConnectionReconfiguration message transmitted is added.
Option 4: Detection of a specific error condition in the DeNB cell, and each error occurrence is added.
Explanation: According to the text, transmission of the RRC ConnectionReconfiguration message to UE triggers an attempt of an outgoing intra-eNB handover from DeNB cell to RN. As a result, each RRCConnectionReconfiguration message transmitted is added to the relevant per handover cause measurement. This ensures accurate counting of attempted handovers and their causes.