How to inform the UE about the change in CIO (cell individual offset) if my ENB has more that 32 neighbor cells

Question

In LTE, number of cells in is caped to 32 in MeasObject->CellAddModList.
My ENB is has detected the more that 32 neighbor cells through ANR and there CIO is changes regularly as part of MRO feature.

So if CIO of all neighbor cells changes regularly how do i inform UEs about the latest CIO. Does UE stored the last CIO provided in its database even after a cell is removed from CellAddModLIst?

Please provide your inputs.

Thanks,
Pradeep

Answer 1

"if CIO of all neighbor cells changes regularly how do i inform UEs about the latest CIO"

Typically operators configure the MRO algorithm to run during the OFF hours when there is no traffic. The MRO algorithm can be configured to run once a day or once a week for eg.

When the CIO changes, then the new CIO there can be 2 options :- a) Either tell all the UEs that the CIO changed by sending an rrc_recfg with measurement change
or
b) Inform only the new UEs about the new cio.

"b)" seems like a more easier to do option than inform all the UEs.

Comments

Thanks Sudeep.
I still have same doubt. Please see the below scenario.

If an ENB has 40 Neighbor cells. MRO algo is ran once and CIO got updated for all the neighbors in ENB Database.
If a new UE admitted, ENB can only send CIO for 32 neighbors (probably first 32 high ranked neighbors of high priority).
If UE triggers Measurement report for HO purpose if it is moving away from the source cell and entering in to neighbor cell coverage area. If this neighbor is not one of 32 cells for which CIO updated. UE considers the CIO as 0 and triggers the MeasResult.
This might result in too early/too late HOs leading the HO failures.

Does UE stores the CIO for more than 32 neighbor cells? Is there a way we can resolve this issue or we need to leave with this limitation

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I think this would be more like a limitation.

I think 32 neighbour cells are more than sufficient for the UE to measure and determine the neighbour.

As you have mentioned the eNB must be smart enough to determine which are its best neighbours (maybe it can get this information based on operator configuration) or other SON features like ANR and send only those neighbours' CIO to the UEs.

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Thank you sudeep