Dear Experts,
My question is more over for those who engage with NR Optimization recently with edge RAN Release NR 20.Q2&3.
We have recently activated A2 NR release functionality in our network, after that we observed sudden degradation in pmEndcPSCellChangeSuccInterSgnb was reduce to 90%.
What’s the threshold for A2 in dBm?
Did you consider this scenario: there are cases when A2 and A3 events overlap so in this case A3 is canceled and A2 takes priority hence A3 events(scg cell change) ends abnormally.
A2 release at -120 dbm.
Is this scg degradation in all network or just some cells?
Only for those sites where we activated A2 Event on NR.
Rest all other side work normally with b1thrreshold functionality.
Actually we are working on the edge of NR Software release Nr.20.Q3 … So very less information is available for troubleshooting for Ericsson CPI
No failure counter yet introduced by ericsson system.
Reduce A2 further like -125 dBm and you will see that scg cell change will improve.
Reducing A2 here in actual partially disabling it.
Lower you go, its more ineffective.
So this is workaround.
Thanks @RFSpecialist, I am also thinking in same direction.
Because my network LTE A2 Critical is set on -124 dBm.
So if we do the alignment B/W LTE and NR, it must be set to atleast -124 dBm.
Just curious to know what technically wrong after activation of A2, why SCellChange performance degraded so seriously?
But here investigation is required, for which event priority is given by gNB A2 or A3.
If both received simultaneously.
You have to actually dig out UE logs and gNB logs.
Difficult to guess.
Yeah… We are capturing CTR and UE logs for this issue.
Hope the analysis help to find the root cause.
Mainly the purpose to introduce EventA2 in latest release of Ericsson is like.
UE will release NR leg (Normaly Based on NR RSRP) and do re call setup.
Without A2 event, it’s based on B1 threshold. Once it’s met, UE release NR leg Abnormally and Count as a ENDC drop.
Do Ericsson gives counters like A3-RSRP etc?
From that we can get what was serving cell RSRP when event A3 was triggered.
And then compare with A2 Threshold.
Such counter even is not available on Ericsson LTE.
For that we can only to refer to the UE trace about RSRP value at A3 event trigger point.
I believe scenario of failure is this one: UE sends measurement report A3 event in uplink. Then the SCG cell change procedure is ongoing. During this ongoing procedure the A2 events is reported by UE so gNodeB rushes to release the scg bearer and ends A3 procedure abnormally. What it is interesting here is why does it happen only intergNodeB and not also during intragNodeB?
Anyway I think you have a 5G coverage at the limit with large coverage holes and no dominance since you face this problem. Usually A3 events happens at high RSRPs like higher than -100 dBm (good overlapping between cells) not at values like -120 dBm.
It may be that you don’t have the proper tilts fo ra 5G cell. All tilts in 5G start from 7-8 degrees and go up to 12-15 degrees in residential area with intersite distance like 300-500m. It is recommended to have mechanical tilt and not electrical tilt because electrical tilt will reduce the gain of the AAU.
Right only intergNodeB, no issue at all on intragNodeB.
In such case even if i change to -124 or -130 dBm, it’s no use.
In case scenario you explained is applicable.
Just thinking: intragNodeB changes happens at really good RSRPs, no way to overlapp with A2 events. Maybe this is the reason.
What should be done to avoid this situation except tilts changes at this moment?
Parameters are more feasible for me to tune.
Check if you have plenty of RLF or beam failures.
This indicates a large number of coverage holes in 5G.
Then this is your case.
Lack of dominance (basically continous A3 ping-pong events) and poor RSRP areas.
Already checked, no major change in RLF failures count. Looks still same.
It doesn’t have to increase after A2 activation. Actually it will decrease after A2 activation, but if still high means you have coverage holes.
Coverage holes and no dominance area.
What you can do you can increase the A3 TTT.
This will reduce the number of drops with disadvantage that it will decrease throughput during A3 events and may increase drop rate.
I wanted to say “This will reduce the number fo A3 events”.
1 Like