Check NSA primary path (LTE or NR) from UE log

Hi all.
In an NSA UE log, when SCG is setup in the RRC Connection reconfiguration, how can we see which is the primary path: LTE or NR from UE log only (not from OSS parameters).

I think by keyToUse in RrcReconf.

keyToUse have value Primary or Secondary.
But it does not tell whether Primary os LTE or NR.
Apparently in EN-DC, Primary is always LTE.

Thanks a lot.
In my case I see key to use secondary which means NR.
And uldatasplitthreshold b1600.

But how do we know which is for UL and which is for DL primary path used?
I am interested in Uplink.

Primary path.
Cellgroup 1 means SCG and Cellgroup 0 means MCG. This indicate the UL path used.

I think keytoUse is only for security key derivation.
Not the path info.

Also this is correct.
For DL… There’s no RRC IE.

Thank you, are right.

Maybe because UE does not need to know this.

Yes. It’s related to security key, not the path.

keytoUse indicated PDCP used.

Exactly :+1:t2:.
Network knows the split for DL, UE is required in UL.
In short, this param is for UL split. In securityConfig.

For this split, if the total data volume is greater than this threshold, PDCP PDUs goes to two RLC entities.
If less, then goes to primary only.

Yes :+1:t3:

Also throughtput values.
If you are able to see at different for different layer.
Scg terminated split bearer will have negligible pdcp throughput for LTE.

Yes. And when eNB want all the UL data to flow through LTE UL, (UL Path switching feature).
It configures UL data threshold to “Infinity”.

Will cellgroup as 0

Yes, correct.
In UL Path switching feature, path switching RRC reconfiguration is sent by gNB.
It is controlled by SCG.

Are we sure is not buffer size higher than this threshold to start splitting data?