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In SRVCC PS-CS initiated.Why not PS-PS voice calls in SRVCC as 3G network is there to support handover for packet call ?

+1 vote
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In SRVCC PS-CS initiated.Why not PS-PS voice calls in SRVCC as 3G network is there to support handover for packet call ?
posted Aug 30, 2017 by Mohit Mohan

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2 Answers

+1 vote

Hi,
SRVCC works in VOLTE ,
For LATE PS call there is a feature called CSFB with PSHO , it will redirect PS services to 3G network without disrupting PS connection.

Thanks

answer Aug 31, 2017 by Manish Vyas
*LTE PS call
+1 vote

In LTE , VoLTE is handled through IMS but actually it is ps call and in 3G voice call is cs call. So in srvcc ps to cs handover happens for voice call.
Suppose if 3g also allow voice call through ps NW with IMS then I think ps-ps handover can happen in srvcc from LTE to 3G.

answer Aug 31, 2017 by Veer Pal Singh Yadav
Agreed by Veer !!
In 3G voice call through PS network or IMS not happen may be because of difference in  acceptable packet delay and frame size structure of two different technology.
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+4 votes

Is there any option is the LTE handset by which when UE makes a voice call it goes through legacy network 2G/3G and for data it uses LTE network assuming LTE network supports LTE data/VoLTE/Legacy Network ?

0 votes

VoLTE is the prominent solution of voice call in the LTE network. VoLTE uses IMS infrastructure to provide voice services in LTE network. IMS network is not new in the telecom, it is quite old solution for voice call across the different network (circuit switch / packet switch ). How does IMS network provide better services through LTE devices as compare to 2G/3G ?

+3 votes

Referring to the 3GPP 29.272 the "Homogeneous Support of IMS Voice Over PS Sessions " AVP is set to TRUE in the ULR means that the serving MME can provide the IMS voice support homogeneously in all TA assigned to it.
Does the MME insert this AVP in the ULR message only if the UE required voice service over IMS during the attach procedure.
In other word, if this AVP is present in the ULR, can we conclude that the UE support Voice call over IMS (VOLTE).

In the same context, if this AVP is absent ("Homogeneous Support of IMS Voice Over PS Sessions ")m can we conclude that either the MME does not support VOLTE at all or the UE does not support it (but only CSFB?

0 votes

There is an AVP 1493 (Homogeneous Support of IMS Voice Over PS Sessions) that might be sent or not within ULR message. According to 29.272, this AVP is presented in ULR if either all TA/RA of the MME homogeneously support VoLTE (AVP 1493=Supported) or non of RA/TA of the MME supports VoLTE (AVP 1493=Not_Supported). According to 29.272, the AVP 1493 value =“NOT SUPPORTED” may also indicate the lack of VoLTE roaming agreement between HPMN and VPMN. AVP 1493 is not presented in ULR if some of RA/TA support VoLTE and some not or MME has no info about VoLTE support.

I have several questions:
1. I assume MME will not include the AVP 1493 in ULR if UE has not requested voice over PS. Is this correct?
2. Whether MME inserts the AVP 1493=Not_Supported in ULR towards HPMN when there is no VoLTE roaming agreement irrespectively to UE request for voice over PS or only when UE has requested for voice over PS?
3. How MME decides about VoLTE support on TA/RA level(configuration, dynamic conditions etc.)?
4. What could be scenario when MME has no info about VoLTE support?
5. Whether the case when AVP 1493 is not presented in ULR due to reasons defined in 29.272 is common or it is just intermediate state while VoLTE deployment?

+1 vote
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