Can anyone tell me the only difference and views between CSFB and VOLTE?

Question

Hi All,

I want to know, various types of Attach Request for Phone and Wifi devices and what will be the respective attach Accept response from the network in successful Case. I am looking for Network response both in case if network supports VoLTE (Like RJIO)and if network doesnot supports volte (Airtel)....

Answer 1

As CSFB stands for Circuit switch fallback, UE gets voice services through legacy infrastructure (2G/3G CS) while in case of VoLTE, UE will use same LTE infrastructure for voice as well as for data services. Being in LTE network, user can make a voice call through LTE network as well as data services can be continued. In case of CSFB, it depends on dual transfer mode support from network side as well as from UE side. If both UE and legacy network support DTM (dual transmission mode) then UE can continue voice along with its data session through the legacy network in which it is connected for voice services.

Answer 2

LTE/SAE provides connectivity towards PS domain and supports packet based
services only. That implies that traditional CS services such as CS Voice, CS
Data, SMS are not supported. In order to provide smooth migration CS Fallback (CSFB)
solution is provided by 3GPP. ( An LTE Terminal cannot transmit/receive in GSM or WCDMA whilst attached to LTE)

VoLTE provides a first line line telephony service over ip in an LTE network with; Attractive new (MM) services, Faster setup time, Efficient radio usage, Long term target/vision, network consolidation.