What can be the reason of 100% IRAT (4G to 5G) Handover getting failed in Preparation phase?

Dear Experts.

What can be the reason of 100% IRAT (4G to 5G) Handover getting failed in Preparation phase?

ANR is activated for LTE to NR NBR Addition.

What do you mean by preparation phase?

Ho_require is being sent out or not? You can confirm from log.

HO Require is sent.

Check for target log, if this has been received.

And log / call flow in target gNB.

Thanks. But I have only OSS KPIs…

Dear Experts.

4G eNB is having 100% IRAT HO Preparation fail with nearby 5G gNB.

I have the parameter & configuration setting which are required for IRAT HO-No issue in configuration.

Can anyone suggest what else can be checked… till the time I have asked DT to collect UE Logs.

IRAT HO success rate is 0… HO’s are getting failed with Multiple gNB.

Check PCI collision, overshooting cells.

There are some feature that show an alert of collisions.

Quick win actions to do blacklisting.

Yes I have checked No PCI Collision.

Problem is Handover’s are getting failed with all the IRAT NBR’s (5G NBR).

Ishoallowed is enabled?

All frequencies are defined with LTE?

Yes ANR is active and ishoallowed is true.

Yes all NR frequencies defined with LTE.

Termpointtognb is allowed?

Check plmn list parameter config settings in 4G.Make sure to have Gutrancellrelation with all nearby 5G cells.

Is it MOCN config?

Checking B1thresh in Ntcellutra mo will help but it never show 100℅ fail.

Mostly those checks resolve issues.

Have you checked Target 5G Cell KPI are OK?

How about 5G Cell Status/Any Alarm?

And how about Interference NI value high of target 5G cell?

If HO is 100% fail, you can check target cell KPIs, check any transmission issue on target, ping the target nodes.

What is NtcellUtra?
I haven’t seen it in E//.

4G site is Samsung & 5G(SA) Site is Ericsson.

Failure are happening only with single site.

Already Reset given, all parameters compared with other okay sites but no issue found?..

But if everything is okay, failures can’t happen…


Can you list the parameters that you’ve checked from both LTE and NR end, please?

This 4G Site is having 100% IRAT Failure with All the NBR 5G SA Sites.

NR Frequency, B2 Event, NR Measurement-Event A1, MME configuration-N26 Interface, TAC definition at AMF, S1 AP Version.

S1 UP reachability.

Did you do PCI change in 5G node recently?

If yes, same needs to be update in 4G Samsung NRT.

Please delete the 4G–>5G neighbor relations.

UE based ANR at Samsung end will recreate it with correct new PCIs by DLT-NBR-NR or will change PCI by CHG-NBR-NR.

I have checked the NRT Table and all the NBR’s are created with UE Based ANR only.

And if any PCI is getting changed at 5G than it will be automatically updated in 4G-NRT Table. Still I have to delete the NBR?

We have an observation that NRT update does not happen everytime properly.

If it is possible, a neighbor refresh can be done.

Ok. I will get the NBR flush done.

One more observation: I have checked the UE logs and found that UE is sending measurement report continuously but HO command is not seen.