VoLTE Inter-PLMN Handover problems

Mobility
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Hello Experts,

I am having an issue (no SRVCC, high CDR - Call Drop Ratio) with Inter-PLMN Handover for VoLTE call between two areas of same operator.
A VoLTE session with PLMN A gets dropped and again need to initiate call while latching to PLMN B.

I have same MME and SGW.
I have done PLMN whitelisting parameter configuration at RAN end.
But the issue is still persisting.
Do you have any MOP/case study on what parameter settings needs to be set in CORE?

Thanks in advance.

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Are these PLMNs configured as equivalent PLMNs on the CN? You can see this info on the UE side, for example in the ATTACH accept, and on traces in the initial context setup

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Hi @marcengo,

As per information shared by Core team, e-PLMN HO defined against TAC…
We are planning to send DT team and conduct online trace.
Any parameter that needs to be set in SGW?

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In enb, all MMEs of other plmn enb also to b defined means both enbs of both plmn should have neighbor mme added. Also all TACs in inter plmn to be added.
Then earfcn of inter plmn to be added for frequency definition. And then all a1,a2,a3,a5 should be active against that freq definitions.

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Hi Onkar,

Please find my comments–>

In enb, all MMEs of other plmn enb also to b defined means both enbs of both plmn should have neighbor mme added. Comment: Same mme for both the circles
Also all TACs in inter plmn to be added–>Comment: eplmn vs adjacent tac mapping done
Then earfcn of inter plmn to be added for frequency definition. And then all a1,a2,a3,a5 should be active against that freq definitions. Comment: eutranfreqrel created with adjacent plmn -earfcn. Adjacent plmn defined in “additionalPlmnList” ; “plmnWhiteListEnabled” set to true, adjacent plmn added in "plmnWhiteList’ in plmninfo MO

I am more keen to know what are the settings to be done in core (MME and SGW)

Thanks

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No setting required in sgw, in mme just tacs of inter plmn enb to be defined in my network. Inter plmn works perfectly fine