LTE: Measurement with CGI report and ANR

ANR:

Automatic Neighbor Relation is one of the SON features where SON(ANRF: Automatic neighbor relation function) instruct the UE to detect unknown cells and report them to eNB. These unknown cells can be Intra-frequency, Inter-frequency and Inter-RAT.

Intra-frequency: Same carrier frequency, can be of different bandwidths.
Inter-frequency: Different carrier frequency as compared to the serving cell.
Inter-RAT: UTRAN, GERAN.

In LTE, the operator is relieved from the duty of handling neighbour information. The ANR functionality resides with the eNB and it is responsible for creation/updation/deletion of NEIGHBOUR RELATION.

eNB:

1. The procedure of building the NRT lies with eNB. eNB initiates the procedure by asking the UE to start and send measurement of nCell (NEIGHBOUR CELL).

2. Here, UE plays the role of identifying the neighbour cell, measuring the signal strength (RSRP/RSRQ) and informing the serving eNB.

3. eNB receives the Measurement Report of the nCell which contains the E-UTRAN CELL GLOBAL IDENTITY of the neighbour cell.

MME:

1. The serving eNB gets in touch with MME (if an X2 connection doesn’t exist) to assist it-self for creating a X2 tunnel with the target eNB. Once when this tunnel (IPSec and SCTP) is established, the serving cell eNB forwards the CGI-info to the target eNB. Thus, both the eNB's updates its own respective NRT (NEIGHBOUR RELATION TABLE).