Hi Experts!
We are investigating a problem that occur in LAB LTE ENB (Baicells) when trying to integrate at Core (ZTE).
Everything seems to be fine: UE’s attach, RRC connection Sets up but, when traffic should happen some (not all UE) show “radio link failure cqi detect expired”.
At LAB environment there is good RSRP and SNR for all UE.
Has anyone got any guess on it?
This happens at the session first beginning.
In the logs, do you see any CQI reports, CSI( PMI,CQI,RI)?
Radio link failures have nothing to do with Core, to my knowledge…
I agree.
Checking in the LAB if there is any CQI Reports.
This cause is sent by enb to mme whenever the RLF detection is activated. When this feature is enabled , enb checks for the rlf based on cqi.
If the cqi is not send by ue or not receive by enb within the specific time, enb will release rrc and send release message to mme with radio connection with ue lost.
Could be if the head of the package could not be handled by both.
Update everyone: This case was solved last week.
We found out that UE attach needed a QCI that was not enabled at Core. Although our network is Packet only private LTE, the phone only connected when we configured Combined Attach and included QCI-9 as valid.
For CPE it was always ok, but the phone somehow ignores it is a private data only network and still requires combined attach in order to get in.
The “Radio Link Failure” message was logged by Core making it look like it was an RF problem, but RRC / SCTP logs showed the QCI reason at radio side in NAS layer.
Don’t mix up CQI and QCI. But in this case, both appear in analysis. QCI was the reson.