Automatic Neighbor Relation (ANR) measurements

Hi all,

I’ve been looking into the ANR feature and I’m having trouble to understand how can the UE measure/detect a new neighbor (that is not yet in the serving cell’s neighbor table).

To my understanding, once the neighbor is in the serving cell’s table, the base station can provide the UE with the SSB-based RRM Measurement Timing Configuration and the UE will know where/when to measure.

But what happens when the neighbor is NOT in the serving cell’s table? How does the UE knows where/when to perform the measurements (specially in NR where the SSB is not necessarily in the center frequency)?

I’d appreciate if you can shed some light on this!

When the UE reports Measurement report with PCI information and the serving gNB is unable to find it in the Neighbor Relation table.

The Serving gNodeB instruct the UE to retrieve the CGI information of the target cell.

Possibly, the UE also needs to be configured with a measurement gap or DRX.

The UE detects and decodes also the RMSI (System Information Block#1) from the target cell in order to retrieve the CGI.

The retrieved CGI is stored and reported to the serving gNodeB. From the reported CGI, the serving gNodeB can extract the gNodeB ID, which is a part of the CGI and other information to update the NRT.

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Thanks for your reply!

But it still unclear for me how the UE will perform the measurement (and find the PCI) in the first place, specially in NR. In NR, the SSB configuration is a lot more flexible in term of where it can be placed in time and frequency.
So, for instance, assuming the SSB periodicity in NR is 20 ms (5G | ShareTechnote), then, we’d have to schedule a 20 ms gap to be able to catch all possible SSBs? Would we also have to scan all GSCN (Global Synchronization Raster Channel) within the cell bandwidth to make sure we cover all possible neighboring cells?

Thanks a lot!

gnb/enb sends report cgi config to UE to measure the NRCELL from SIB1. First you have to activate SIB1 on NR cells for UE to decode it. If it is intra freq , UE will be pushed to enter DRX , and drx long cycle should be bigger than 160 ms or ANR drx if configured. unless you set ssb to bigger than 160 ms it is fine, 20 ms is the most common value for ssb periodicity.


@gzilli “neighboring frequency” information including SMTC is a prerequisite for ANR to populate “neighboring cell” information in the neighboring relation table

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Check this, it will help:

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Hello Guys.

I’m not a CORE engineer so I have a doubt:

ANR gets the MRs from UEs.

After that, ANR decides to create the X2 link and the neighbor relation, so ANR asks DNS for the peer IP, right?

Is that DNS part of the MME?

Not very clear about this part

Hello Bro,
Actually MME is a main part for identifying and adding IP address of target CGI NBRs. IP address is derived via S1 SON Information exchange → which is IEs in MSG S1aP.eNB Configuration transfer


Also please check below link :

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