SRVCC preparation failure

4G LTE
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1

Hello Experts.
For SRVCC to GSM at what nodes we have to define in the legacy network?
I m getting SRVCC preparation failure due to Destination preparation failure.

2

Check target cell CGI it all are correct and live.
If inter site distance is high then tune b2 thresholds.

3

Which are the nodes need to check?
Checked at EnodeB and GCS. At both end it’s correct only.

4

Srvcc preparations fail for particular relation?

5

All the relations.

6

Check in any change in LAC for iRAT neighbours.

7

How much is ur B2 thrsh 1&2? And offsets?

8

No change in LAC, after PLMN changed issue started.

9

Vendor?
Check Which type of SRVCC the eNodeB initiate.
For Huawei, the eNodeB can initiate a CS and PS SRVCC procedure or eNodeB can initiate CS-only. If MME or the RNC doesn’t support you can set only for CS (CsPsHOInd false).

10

Vendor is ZTE, and its initiate only CS handover.

11

Check:
Retry and penalty…

12

As far as I know, SRVCC HO indication only impact on SRVCC execution instead of preparation.

13

Was there any other action/changes on the Core?
Like MGW migration to Open MGW or else?

14

No, there wasn’t any other changes.

15

The basic concept to SRVCC to happen…

  1. the feature state should be activated on eNodeB (SRVCC handover to GERAN) and
  2. VoicePriority should be enabled from LTE to GSM frequency.
16

Handover Routing is one point can be checked at CORE.

17

Hi, I’m also facing this issue
Srvcc preparation failure toward some BSCs and RNCs…any checklist available for troubleshooting the issue

1 Like
18

Kindly check the below points for SRVCC prep fail on initial stage,

  1. Is target cell overloaded?
  2. Is target cell unavailable?
  3. TAC not define
  4. License/Software issue
19

Upon analysis we identified that the issue is mainly towards certain RNCs/BSCs in the network. ( Srvcc pre success rate is only <50% toward these nodes) …No issue with other nodes.

Based on DT carried out are observing SRvcc fails and dropped calls with cause channel release blocked call and sourse node is not getting " prepare handover response message" from targeted msc

20

Is both source and target belong to same MME group, any critical alarm? Failure on only one target Enodeb or specific cell?
Is target site in sleeping mode, check traffic?