S1AP INITIAL CONTEXT FAIL due to interaction with other procedure

During S1 interface tracing we found S1AP INITIAL CONTEXT FAIL due to interaction with other procedure.
Can anyone help with solution?


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Please check the RRC connection message before the initial context message , to know what was the requested service.

This generally happen due to poor UL coverage.
Check your cell, probably it would be having high TA.

Either high TA or High interference (or both) causes UL signal distortion.

You need to identify the cause by corelating with UU traces. Mostly l.e-rab.failest.mme with cause ‘Normal Release’ are due to:

  1. MT-Access during E-Rab Establishment of Mo Data. (80% of times)
  2. Repeated access by UE due to expiry of T3417 (SERVICE REQUEST sent EXTENDED SERVICE REQUEST also sent) which is 5 sec. (15% of times)
  3. MME waits for the completion of initial context setup for 10 sec typically, expires too. (5% of times)

UE is in handover progress, source enb already sent HO preparation require to MME or other enb. During Handover, UE has service request of Csfb mo/mt, and csfb also initiated by mme sent s1ap context setup request. But enb found it conflict with HO procedure, so enb reply with context setup failure due to interaction.

Solution: it has one parameter to prefer csfb during ho. Enb will cancel handover, process csfb.