ed or uninitiated Connection re-establishment Radio link failure detection RRCtoX2RLFMessage X2 AP: RLF Indicator X2APtoMRORLFMessage Too Late handover detection Figure 2-14. How a late handover is handled as part of the MRO solution CHAPTER 2 SELF-ORGANIZING NETWORKS IN LTE DEPLOYMENT Early Handovers Early handovers often result in a radio link failure for a UE that has been handed over to a target cell after handover is complete. Often in an early handover case, the UE tries to reestablish the radio links with the previous source eNodeB upon radio link failure. A very popular means to reduce or check on early handover failures is to detect such RRC reestablishment messages sent across from the UE to the source eNodeB and then send across an RLF indicator to the target eNodeB where the radio link failure occurred. The target eNodeB then recognizes the UE as the one that was originally handed over from the same eNodeB and sends across a handover report message to the original source eNodeB, thereby indicating this as an early handover case. In the source eNodeB, upon detecting this case as an early handover case, appropriate adjustments to the CIO for that particular neighbor can be carried out so the percentage of late handovers is reduced for the cell pair. This mechanism is described in detail in Section 22.4.2 of TS 36.300-990. RLF indicator message and handover report message are described in Sections 8.3.9 and 8.3.10 of TS 36.423-960. For cases where the source as well as the destination cell pairs belong to the same eNodeB, there will not be any X2 messaging to pass on the RLF indicator or the handover report. Instead, the MRO corrective action will be taken care of by the eNodeB internally. Figure 2-15 shows an example of how a too early handover case is handled as a part of the MRO solution. Cell belonging Cell belonging to eNodeB B to eNodeB A X2 AP X2 AP handover completion Connection re-establ shment Radio link failure detection RRCtoX2RLFMessage X2 AP: RLF indicator X2 AP: hand ver report X2APtoMRORL