No Layer 3 message after B1 event

5G NR
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1

Hello, a question for 5G NSA Experts,
I’m connected to LTE network.
I’m trying to do sgNB addition to 5G.
But after reading B1 measurement I did not receive any layer 3 message.
What could be the reason?
(Keeping in mind our trigger conditions is RSRP and sgNB level is stronger than threshold)

2

In your case seems SCG addition fail over X2, which you can’t seen in L3 message.
Better to capture Core traces as well in parallel to check exact reason.
If you cant’t capture Core traces, take help of counters, for example SCG addition fail reason, etc.

By the way, are you able to see measurement report from UE to network for NR cell measurement using B1 or B2 event?

3

I seen B1.
But X2 is up and no issues.

4

Then you must see RRC reconfiguration message indicating SCG addition successful.
But in your case no message, so I assume UE get lost.

I even find same issue: It can be due to wrong value of configured nr arfcn.
You need to check system counter carefully.

5

No I did not.

6

I mean not in L3 but Core network traces or system counter.
If it’s fail then at least you can find reason.

7

Any LTE L3 message or NR L3 you are not receiving? If first, your data collection tool is broken, or your UE went into RLF. If second, then it is normal, no NR L3 messages unless some NR PSCELL change measurement reports and such, but you may not see them right after the NR PSCELL addition.

8

Possible causes

  1. Missing X2 between eNodeB and gNodeb
  2. X2 is down
  3. UE capability is not matching network capability (e.g DSS on network but not on UE)
  4. gNodeB is congested ( e.g. licnese limit reached)
9

I have same problem but I can not receive any measurement report although proper configurations are sent to UE. Any suggestions if you have encountered such an issue?