Deep Dive into 5G Voice EPS Fallback “Everything You Need to Know”

[@AbbasNasser-yk2ku]

Great effort in covering the topic E2E and in details , Keep going

[@mohamedeladawiashour]

Thank you

[@MohamedHassan-mo3zo]

Very clear as usual . 👌

[@mohamedeladawiashour]

Thank you

[@georgioskarouzos7418]

Hello Mohamed! In case a VoNR capable Ue initiates a VoNR call in SA area and starts moving to 4G area, then VoNR to VoLTE measurement-based IRAT handover will take place. Is it correct? If blind or measurement-based Redirection occurs, then this is considered as VoNR drop. Is it correct ? Thank you

[@mohamedeladawiashour]

Hi Georgie, you are correct. As far as I know, blind redirection or redirection, in general, shouldn't be considered as an option, assuming it is supported by any vendor. This could result in drops for voice services. I recall a similar concept being applied in VoLTE as well.

[@shoaibakram4399]

amazing video ,thank you

[@mohamedeladawiashour]

You’re welcome. Thanks a lot; shoaib

[@georgioskarouzos7418]

Hello Mohamed, your videos are always very valuable!In case of EPS fallback the Ue performs again IMS registration, now in 4g network, given that Ue 's first ims registration was in SA. Is it correct?Thank you

[@mohamedeladawiashour]

Thanks, Georgie; the Ue needs to do one time registration to IMs even in 4G or 5G; you will not make any need registration even if moved between 4g and 5g only registration is required if ue is out coverage or deregistered from ims. I am not sure if understood your question correctly or not. Let me know on either cases

[@georgioskarouzos7418]

Valuable info Mohamed, way to go!! To my understanding with Sip invite message 5qi 5 is initially established for ims signaling.Then network Pdu session modification message is sent for 5qi 1 dedicated qos flow.Is it correct?

[@mohamedeladawiashour]

Hi George, Yes you are right, You can find the call flow which showing this point at slide 10, you may download the working materials from this link www.mohamedeladawi.com/deep-dive-into-5g-voice-eps-fallback-everything-you-need-to-know/

[@georgioskarouzos7418]

@@mohamedeladawiashour Thank you very much

[@mcla5220]

Hi expert, I'm an engineer working in Network operator in Vietnam I have several questions In SA how to reduce the call setup time for EPSFB and CSFB? I have tried Blind redirection but the CST still about 6-7s (MO) Maybe just use the handover for EPSFB call, I think the redirection will waste more time than

[@mohamedeladawiashour]

Hello, my friend. While blind redirection typically improves EPSFB setup time delay by a few milliseconds (approximately 200-300 ms), it is generally not recommended for various reasons. If you’re aiming to enhance EPSFB setup time, the focus should be on optimizations from both the AMF and IMS sides. From the RAN perspective, your options are limited to adjusting the paging DRX cycle to enable faster decoding of SIB1 after reselection. This adjustment can lead to improvements in MT EPSFB call setup time delay. Also depend in yiur vendor but sometimes there are features which pritroize voice calls over xn handover this can also procude few ms improvement during epsfb call and xn handover race condition scenario.

[@nizarworld2020]

Kindly explain configuration level as deep dive which will explore what would have happened in each node. All vendors configuration almost same. Eg; upf discovery of pcscf IP, it's common in all tech exercising to identify dns and IP pool settings.

[@mohamedeladawiashour]

Configuration or you mean call flow detailed level?

[@nizarworld2020]

Ng media to pcscf is missing , either you can ignore upf to immgw or connect pcscf to immgw

[@mohamedeladawiashour]

Thanks for adding this; yes and in general the IMS architecture is not completed in this video; i will consider the detailed one in next video for Vonr and Epsfb