What could be possible reasons of X2-handover failure ?

Question

In case of hub-and-spoke topology, X2 messaging can travel all the way back to an aggregation point, which may be co-located with EPC. In such scenario both X2 and S1 traverses same physical path (a.k.a X2 over S1). Please consider both Intra-MME and Inter-MME handover scenarios. Would X2 based handover in such a case yield advantage over S1 based handover. Thanks.

Answer 1

On behalf of Bart -

Target eNB does not have resources for handovered bearers.
The x2 link dropped during HO
(MANY MANY REASONS.)

Comments

how  x2link dropped?is it using x2setup fail?

---

May be wirecut ??

---

That is a good topic .....
I would also like to know one thing - Suppose if X2 is configured initially but during handover for some reason the X2 link at target end is failed or is not in service then will the handover happen ? Is there any provision at S1 interface to deal with such scenario ?

Thanks & Regards,
Ashutosh

---

This depends on the algorithm implemented at source eNB to trigger handover and this failure at X2 shouldn't occure during handover (but before the HO is triggered). Normally, S1 handover should be a fallback option if X2 link has some issues. There can be multiple reasons where despite having a valid X2 link, source eNB may decide to trigger a S1 handover - one of them could be Gu Group ID not exchanged during X2 setup, MOCN related checks may also cause it.