LTE UE context failures

What are causes of L.UE.CXT.FAILs apart from UE no reply,RNL issues, no radio resource and security mode failure?

below causes of UE contex failure
1)UL interference or External interference
2) release upgrade issue
3)contex failure due to time delay by MME
4)context failure due to procedure interaction


Which timer in MME is responsible here?

Timer T3410 is responsible

After NAS Encryption completes, the MME Send S1AP_INIT_CONTEXT_SETUP_REQ message to enodeb with 15s delay .
The delay message from MME made timer T3410 in UE timeout. So UE didn’t give any response for RRC_UE_CAP_ENQUIRY from enodeb.

enodeb send message CONTEXT_SETUP_Fail with detail information “radio-connection-with-ue-lost”

did a trace. the issue is context failure due to procedure interaction.

Which parameters can help resolve this.


Interaction with other procedure means it is already interacting with an on-going procedure, only it is released, can start another procedure.

CsfbFlowFirstSwitch is using to avoid conflit with X2 or S1 or TAU procedure.

ue context failures are a major contriibutors to my poor 4g attach kpi. I m trying to improve the 4G attach success rate. so should i prioritse erab instead by using erabflowfirstswitch instead?

ErabFlowFirstSwitch: This option specifies the policy for handling the conflicts between handover and bearer procedures. If this option is selected and a handover procedure conflicts with a bearer procedure such as E-RAB setup, modification, or deletion, the eNodeB performs as follows:

  1. If the handover is not for CSFB or the SRVCC procedure conflicts with a QCI 1 E-RAB release procedure, the eNodeB processes the bearer procedure first.

  2. If the handover is for CSFB or the SRVCC procedure conflicts with another E-RAB-related procedure, the eNodeB processes the handover procedure first.

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so it doesn’t prioritise the erab setup. I misunderstood this switch.

it will prioritise the erab setup over X2 and S1 HO and TAU

but not for CSFB and SRVCC because voice has high priority

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Ahhh, i get it now. thanks alot

you are welcome

Would you happen to know the equivalent of erabflowswitch on ZTE?

not found same parameter

@cheikh789 M trying to locate the other procedure it is interacting with before the s1 ap message saying interaction with other procedure but i cant see any handover only rrc reconfig. see messages before failure message. could it be its conflicting with the re config

Regarding the RIP in general is failing the RRC Connection Reconfiguration .

Mean:eNB does not receive rrcConnectionReconfigurationComplete from some UEs after sending RRC Connection Reconfiguration to them.

you can check below KPI for (SRB2):Initial E-RAB Setup Success Ratio =L.E-RAB.InitSuccEst.QCI.9/L.E-RAB.InitAttEst.QCI.9 and also UuMessageWaitingTimer

increased uu timer no improvement. it still says procedure interaction in s1ap context failure message. but each time i get that failure just like in image above, i dont see and response message from UE for Security CMD and RRC RECONFIG.

and rrc reconfig message contains srb not handover command

how about coverage RSRP during S1ap contex failure and what is value L.SecurMode.Fail

how can

its zero,

issue is on network scale ,not particular cell.
When random trace is done on USN it picks up on diffrent enode bs diffrent subscriber.

and RSRP during trace ?