ANR is used to update eNB neighbour table automatically and eNB uses these neighbour list for HO . ENB can discover new neighbour using UE measurement when ANR is enabled.
Enb can configure periodic measurement or event based measurement for neighbour cell meas. UE will report neighbour meas with neighbor cell PCI. If neighbour PCI is not available in nrt then eNB can request to UE to reportcgi of the neighbour cell. UE will read the sib1 of neighbour cell and will send the CGI through measurement.
After getting reportcgi, eNB will add it in nrt .