When does source cell ask UEs to send ECGI of a neighbor cell under the context of ANR ?

Question

Need to organize Neighbor List by using EARFCN. Any help will be appreciate.

Answer 1

ANR is one of the SON features, used to establish connection between two cells which are neighbor to each other and belong to different eNodeBs. ANR stands for Automatic Neighbor Relationship. Initially, eNodeB configures UEs to get cells information neighbor to that cell. UE sends measurement reports to source cell, carries PCI "Physical Cell Identity" . If cell is not aware about physical cell identity reported by UE then cell may configure UEs to report ECGI, TAC and broad casted PLMNs for a detected neighbor cell.

Once cell receives ECGI of neighbor cell, it resolves ECGI to transport layer address for making X2 setup connection.

Answer 2

Go through these points and u will get ur answer.

1.See every cell has two identities PCI and ECGI, PCI is not unique in an area of large number of cells as its range is [0 - 503] so there is chances of same PCI for two cells nearer to each other.But ECGI is globally unique id for a cell.
2. we get PCI info from PSS and SSS and while measurement also UE acquires in the same way, but to read ECGI of the cell it needs time as SIB1 is transmitted with periodicity of 80ms, so UE has to wait till he reads SIB1 for all the cells having good strength but we will use only one cell to do handover so instead of wasting time and syncing with neighbour cell , while sending initial measurement report it sends neighbor cells PCI, but after again eNB decides to do Hanover to particular cell for that PCI as input eNB asks ECGI for it so that he can know the cell uniquely.
3.After acquiring ECGI of neighbor cell eNB can trigger handover but we need transport layer info of the target cell so either we can ask OAM for the transport layer or we can use S1Ap interface ENB Configuration transfer message to extract target cell transport info by sending ECGI as input. [IF both eNB connected to same MME]

Hope it is clear.