GURATION TRANSFER with eNode81 TNL configuration information Figure 2-8. IP address resolution procedure CHAPTER 2 SELF-ORGANIZING NETWORKS IN LTE DEPLOYMENT X2 Connection Setup with Neighbor Cell Configuration Updates When the transport network layer configuration is received, the source eNodeB can then initiate an X2 connection setup with the target eNodeB. As a part of the X2 setup procedure, the two eNodeBs will exchange the list of serving cells with the respective eNodeBs. With this information, the eNodeBs can update the existing neighbor list with the new set of cells. The procedure is illustrated in Figure 2-9. eNodeB2 eNodeB1 MME CONFIGURATION TRANSFER with eNodeB1s X2 TNL configuration information IP tunnel establishment between the 2 eNodeBs SCTP establishment X2 SETUP REQUEST (eNodeB-ID, served cells information Neighbor cell table update on X2 SETUP RESPONSE eNodeB1 eNodeB-ID, served cells information) Neighbor cell table update on eNodeB2 Figure 2-9. X2 setup and exchange of configurations between the two eNodeBs Neighbor Relation Optimization Broadly, there are two types of neighbor relations. First, there is a neighbor site relation, wherein there is a direct X2 connection existing between the two sites. In this case, the communication link between the two neighbors is known. Second, there is a neighbor cell relation, wherein the given two cells have a common or overlapping coverage area. UE always reposts a neighbor cell relation, but never a neighbor site relation, and only properly configured neighboring relations are relevant for handover performance figures. Figure 2-10 depicts these relations. CHAPTER 2 SELF-ORGANIZING NETWORKS IN LTE DEPLOYMENT X2-AP connection exists ENodeB 1 ENodeB 2 Neighbor relation PCI 6 PCI 5 PCI 4 No neighbor relation Figure 2-10. Neighbor cell and site relations Referring to the example given in Figure 2-10: The eNodeB 1 has an X2 connection to the eNodeB 2 to neighbor site relation The eNodeB 2 parents three cells with PCIDs PCI 4, PCI 5, and PCI 6 A neighbor cell