ERAB modification fail due to radio interface procedure in EnodeB Nokia

Question

does anyone have an idea about sudden increase in ERAB modification fail due to radio interface procedure in EnodeB Nokia FL15A ?
This was launched after spliting TAC_1 in TAC_1 + TAC_2 in order ot reduce the signalling in MME.
But rollback was done and problem still not resolved.

Answer 1

An eNodeB sends failure when it gets failed to handle ERAB modification procedure with the appropriate cause. Please have a look into the cause value received in ERAB Modify Response for associated ERAB ID. Unsuccessful scenarios have been captured in specification. For example: If E-RAB Modify Request message carries "Invalid" E-RAB ID or "Invalid QoS". Invalid QoS means when E-RAB was establishment then it was non-BGR and now requested to make it a GBR.

Comments

Thanks.
I would like to say that the cause from LTE Counter is "Network Layer Cause": DRB is not ACK by the UE after Timer expiration.
EnodeB waits for the answer for the confirmation of the new DRB sent to UE, after Timer expiration, it send Failure to MME.
Some traces shown that after TAC update in LTE, the UE is moved to 3G
That why no response has been got from the UE.