lication protocol) sent by the eNodeB to the mobility man- agement entity (MME) divided by number of initial context setup request messages (S1 application protocol) sent by MME to the eNodeB. E-RAB drop rate: Number of abnormally released radio bearers leading to release of E-RAB divided by number of successfully setup E-RABs. Intra-LTE handover success rate which can be split further split as follows: Intra-frequency handover preparation success rate; inter-/intra-eNodeB from UE point of view: Number of RRC connection reconfiguration messages with mobility info included (new cell) received by the UE divided by number of measurement reports sent by UE for corresponding event. Intra-frequency handover preparation success rate; inter-/intra-eNodeB from eNodeB point of view: Number of received handover request acknowledgement messages divided by number of sent handover requests (over X2 or S1 for inter-eNodeB and inside eNodeB in case of intra-eNodeB). LTE Key Performance Indicator Optimization Intra-frequency handover execution success rate; inter-/intra-eNodeB from UE point of view: Number of sent RRC connection reconfiguration complete messages divided by number of received RRC connection reconfiguration messages. Intra-frequency handover execution success rate; inter-/intra-eNodeB from source eNodeB point of view: Number of received RRC connection reconfiguration messages by target cell that leads to release request message received by the source cell over X2 or received UE context release command message received over S1 in case of inter-eNodeB handover or successful handover indication delivered inside the eNodeB to source cell in case of intra-eNodeB handover divided by number of sent RRC connection reconfigura- tion complete messages (caused by received handover request acknowledgement over X2 or received handover command over S1). 12.3 Physical Layer Optimization LTE spectral efficiency, limited by inter-cell inference, can be estimated based on channel quality indicator (CQI) values as specified in [1]. O