Automatic Neighbor Relation (ANR) in LTE


Manually adding neighbor cells in network is indeed a very hectic process in GSM & WCDMA Network. While  networks are becoming more and more complex, it is required to find an automatic and a more optimized way of adding neighbor cells.

ANR comes under the umbrella of Self Organizing Networks ( SON) features. ANR relies on UE to detect unknown cells and report them to eNB. There are two major types:

i) UE based ANR
ii) ANR with OAM Support





UE based ANR
·                     No OAM support is required.
·                     UE detects PCI of unknown cell when it needs to do measurement (as configured by network)
·                     In case of inter-frequency or inter-RAT measurements, eNB needs to configure measurement gaps/or DRX so UE can detect PCI to different frequencies as well.
·                     UE reports the unknown PCI to eNB via RRC-Reconfiguration message.
·                     eNB request UE to report Eutran Cell Global ID (ECGI).
·                     UE reports ECGI by reading BCCH channel.
·                     eNB retrieves the IP address from MME to further setup the x2 interface. 





ANR with OAM Support
·                     OAM support is required
·                     Every new eNB registers to OAM and download the table with information of PCI/ECGI/IP related to neighbors
·                      Neighbors also update their own table with new eNB information
·                     Now like "UE based ANR", UE will detect unknown PCI and report it to the eNB
·                     eNB doesn't request for ECGI and does not need support from MME
·                     eNB setups x2 interface with the help of mapping table created in second step above