In SRVCC, which sentence is true?

Interview
1

Q. In SRVCC, which sentence is true?

a) IMS Domain triggers the CS for HO
b) CS Grabs the call from IMS Domain
c) S-CSCF sends the INVITE towards the MSS for HO
d) Radio Triggers the IMS for HO

Check 🔎

:arrow_right: Correct answer: Letter b.

In Single Radio Voice Call Continuity (SRVCC), the CS (Circuit-Switched) domain is responsible for grabbing the ongoing voice session from the IMS domain when a UE moves out of LTE coverage (where VoLTE is used) into a 2G/3G area (where legacy CS voice takes over).

The handover is initiated by the radio access network, but it’s the CS domain that takes over the session, not the IMS initiating the handover. The process ensures voice continuity.

Q. In SRVCC, which sentence is true?

a) :x: IMS Domain triggers the CS for HO
→ Incorrect. The IMS does not initiate the handover; instead, the CS domain handles the session continuation.

b) :white_check_mark: CS Grabs the call from IMS Domain
→ Correct. That is the essence of SRVCC — handover from IMS (VoLTE) to CS voice.

c) :x: S-CSCF sends the INVITE towards the MSS for HO
→ Incorrect. The MSS (Mobile Switching Center Server) is involved, but the INVITE isn’t part of the SRVCC handover signaling.

d) :x: Radio Triggers the IMS for HO
→ Incorrect. The radio may detect degradation, but it does not trigger IMS; rather, it triggers the handover process coordinated by MME and MSC.