Question

During Handover, is it possible to do E-RAB Modification procedure and if YES how we can do it?

Answer 1

As per specification, if handover procedure is ongoing at eNodeB for an UE and at the same time E-RAB establishment/modification request landed up at eNodeB , eNodeB sends failure response to MME for E-RAB related procedure by including cause "S1 intra system Handover triggered or S1 inter system Handover triggered or X2 Handover triggered".

For more details refer following specs:
1. 24.301 (covers interaction of other procedures during handover)
2. 36.413 (refer for the possible cause values)

Comments

is it same procedure while doing INTER-RAT Ho?

Answer 2

There are two interfaces on which handover signalling messages exchanges either with peer eNodeB (using X2) or MME (using S1).

X2 interface is between two eNodeBs and handover signalling between them always related to intra LTE (intra/inter frequency).
But in the case of S1 interface, handover can be (IntraLTE/ LTEtoUTRAN/ LTEtoGERAN) . If UE is moving from LTE to UMTS , on going bearer related procedure will be aborted and once the UE moves to UMTS, it will initiate new bearer related message.

I am still not sure in case of Inter-RAT handover, I answered based on understanding of the LTE system.
Please correct me if I am wrong in this context.
Thanks.