Femtocell Handover issue

RAN
1

Hi everyone, any help is welcome with this LTE behavior:

Two femtocell placed in different floors HO_out to macro is ok HO to Henb fails even when neighbors are defined each other with correct information and no blacklisted.

It’s curious counter HO.fromHenb is not raised per HO.Out attempt from other source… and there is no more femtocells over there.

S1 preparation Failure message is shown cause “handover target not allowed” and also “target cell banned for handover” message is shown sometimes besides Handover not allowed: no candidate target cell in database other cases

Thanks for your attention.

2

I am not sure can x2 link be defined or is x2 available for those two femtocells.

3

Henb indicates you are trying HO to CSG cell from macro cell.
Please check flag is enabled for such special HO.

4

X2 is disable on each femto cell.

5

So x2 is not possible on femtocells.

6

Actually is possible to set up.
But this case is only HO S1 based.

7

But only these two femtocells you are getting s1 ho fail while handover.
And while trying to handover to ther femtocell.

8

Yes, that is the case.

9

What is MME pool of that two femtocells?
Is it same?
If same then it can go through x2 if Links can be defined.
What is TAC and MME pool, is it same?
Of both femtocell?

10

TAC is the same, even though there is MME Pool configured.

11

MME is the same, you mean in both femtocell configuration too with TAC?

12

Yep, but based on your comment I wonder the case where one of the femto has bearer set up with different MME.
It shouldn’t impact because it is MME Pool, should it?

13

I think in same TAC it should be in same MME pool.
It’s weird here.

14

But you could configure TAC per MME as well.

Yep and the messages shown don’t give me a clear hint because neighbors are stated and configured correctly to speak each other :thinking:

15

Check timer t304 in case ho failed in execution.
Apart from flag for CSG.

16

But @ankgitm, this is preparation, as per him.

17

Ok. Then admission control, Tx resources…
All need to check.
Can we get counter pegging there on site?

18

The Flow is as follows:

SHeNb(source HeNB) sent HOrequired to MME, MME sent HO request for THeNB (target) it HOreqACK and for any reason some info there, it is exchanged and SHeNB receives S1 preparation failure instead of HO command.

I ‘ve tried to capture that info exchanged with THeNB but I haven’t been able to do that yet but for the message “handover target not allowed”perhaps some constraint between MME and target HeNB but I don’t think so.

19

I think it’s related to IP or Core.
MME Definition.

20

This happens when a service is not allowed in target cell.
For example if VoLTE is not enabled in target cell a VoLTE call cannot make ho to this targe cell.

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