Hello Experts,
Need your help in improving the LTE ERAB setup SR for Ericsson system.
ERAB SR is < 98%.
Could you please suggest any parameter optimization to improve the ERAB SR?
What is the reason for the degradation?
We have very limited Counter available in Ericsson system to know more about on troubleshooting side, most of time.
It’s hard to get anything from the sub-counter about initial eRAB degradation.
Usually trace would be helpful.
Aren’t there subcounters to indicate if failures due to lack of resources, no reply, MME, etc?
I totally agree, Ericsson has limited counters and actually I was also exploring the reasons of increased Erab Setup Failues too recently.
Trend is going down gradually.
The reason what I see is, traffic is increasing these days due to lockdown and work from home situations.
The same traffic is being generated from bad coverage (indoor/deep indoor) so actually the reason can be bad radio conditions.
Plus extremely high PRB Utilizations are also causing increased DL interference and is adding to already bad bad RF conditions the user is in being indoors.
Capacity shortage will directly impact this KPI too.
So it comes to coverage and capacity mostly when we talk about Erab Setup Success Rate KPI.
Understand, might be we can say like that.
I am looking for any other reason if someone can bring on this forum. Operational issues are an exception and should be kept aside.
One more reason can be S1 Initial Context Setup Timer in MME if the failures are due to MME. Ericsson do not have counters to differentiate between failres due to currency eNodeB or MME but Nokia and Huawei has it I believe. If the failres are happening due to this timer timeout then increasing the timer in the MME can help. Again traces comes into play here to isolate the reason.
I think any 4G issue in accessibility and retainability can be classified in 6 cases:
- No dominance
- Overshooting
- Too much overlapping with neighbouring cells
- Poor uplink
- Coverage holes
- Users in deep indoor
Once we eliminate all of such issues KPIs will come back to normal. CTRs are good to identify which case it is is , cell by cell.
Here is an interesting case of gradual degradation in Erab Setup Success Rate.
Traffic is/has increasing but is not matching with this declining trend.
There are no particular worst performing cases which are the reason for this.
Question is: if it is radio conditions, how it is degrading without any actions in the network?
The decline is on all the layers we have.
Any clue here?
Traffic is high/High PRB Usage too.
Check the reason of failure.
It might be due radio or no resources or no reply (coverage).
I expect this is only LTE without VoLTE, right?
For Erab Setup failure we don’t have counters for reasons, this was already discussed here. 
Right, but LTE or VoLTE?
This is LTE. (And vendor is Ericsson)
VoLTE is also there, question is how radio conditions deteriorated which any major actions in the network.
It might be due no radio resource.
Do you think we should look into MME Timers here?
Check number of connected users per cell and check your configured number of UE license.
Not at this stage.
Try to get VoLTE trace and check from PCAP file using Wireshark.
Of you have any MME release.
I checked the Core traces and cause Core traces said “The-response-from-the-eNodeB-times-out(9949)”.
They are matching the traffic increase with no license issues on RAN part we have enough.
It might be due the UE at low coverage or low RF quality he is not recieving the acknowledgement within the enodb timer.
Please trace the busiest hour.
What was the sinr, rsrq, rsrp?
This is my suspicion too.
These are from MME trace, not from eNodeB. Will check the CTR too.
You have the trace, check the RF.
Oh, ok.