The UE must be capable of reading and reporting CGI. (If a UE capable of reporting CGI is not available, all external cells that are possible neighbor cells must be defined manually.)
For inter-frequency ANR and ANR for UTRAN or GERAN it must of course also support the wanted other frequency.
It must support measurement gaps to measure PCI on other LTE frequencies, scrambling code (SC) of UTRANand Base Station Identity Code (BSIC) of GERAN.
It must support DRX to be able to measure CGI from neighboring cells.