ANR – Automatic Neighbour Relations
The NR management is a key feature of Self Organization Network (SON).
It plays an important role in seamless connectivity. It enables the UE to move from one location to another location without any loss of connection. In traditional systems i.e. before SON , the neighbour relations were defined manually in the OAM. This was mostly done during the pre-launch phase with some of the work at the post launch stage as well. The work done in the post launch usually helped in better optimization of the overall network.It was a tedious task as neighbor cell list would change very frequently for various reasons especially when they are putting a lot of new cells here and there.
So as we can distinguish the ANR function can be used in two cases,
1. Pre Launch
2. Post Launch or Optimization
The ANR function in the eNodeB , If the operator so chooses, the OAM system adds and configures NRs before the eNB goes into operation.
For Optimisation of the neighbourhood list, the ANR function deals with automatic NR additions and removals. It minimizes the need for planning and configuring NRs. If the operator so chooses, the OAM system adds and configures NRs or removes NRs after the eNB goes into operation.
Each cell broadcast the list of neighbour cells via various SIBs.
How a cell knows about the existence of its neighbours ?
A Cell does not have any measurement functionality for detecting the existence it’s neighbour cell. Then how we solve the problem ? This automatic neighbour detection can be possible if UE helps. Since UE can detect all the cells around it, network can order UE to check the existence of cells around it and extract the neighbour cell information from UE report.
Overall procedure is as follows.
1. When the PCI – Physical cell Identity identified by UE does not correspond to any defined relation in the E- Node B
2. CGI – Cell global identity is acquired by the NodeB from the UE
3. Add missing RBS Cell, NR and X2 link
4. A New relation is created.