Monday, 14 September 2015

RRC/RAB establishment failure

Problem Description
There are some sites get highly RRC/RAB establishment failure. And the KPI are affected.

Handling Process
There are not any hardware alarm . And RRC/eRAB Establishment failures happen only start some specific time. Normally will trace the UU/S1 signaling message to find the root issue.

1.Check the KPI degraded detail information. We can see there are a remarkably degrade.  

2. Trace the S1 signaling message the ,Uu & S1 interface on LTE_Kramerville_SGC_3, and found that that the eNB sends InitialContextSetupFailures to
MME with cause 32 i.e.   encryption-and-or-integrity-protection-algorithms-not-supported(32)

3.Trace on the UU interface , and found the allowed ciphering and integrity algorithms sent by the core are shown below.
“eea0” and “spare1” which may get issues or not defined in Core.

4.Report this issue to MME side, and confirmed by the Core engineer, “EEA0” are not configured in the priority list on the MME.
And from the start of LTE the MME did not cater for EEA0.  And they add the “EEA0” to the MME priority list.
         After the implementation, the cells RRC/eRAB establishment failure are reduced to normal.

Budi Prasetyo

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Write comments
25 June 2017 at 03:53 delete

why does this happen or occur sir ?
can you explain or can you provide the hard copy and file for this ?

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