How does voice call happen in 4G LTE mobile networks and why?

How does voice call happen in 4G LTE mobile networks and why?

In the absence of the above CS mechanism for a voice call on a 4G network, LTE networks use a mechanism called Circuit switched Fallback or CSFB. This makes use of the existing 3G and 2G networks and tries to channelize voice communication for 4G, by switching 4G to 3G for a voice call.

What is an LTE session?

LTE attach procedure is the procedure in which the UE registers to the network, and creates the EPS Bearer between the UE and the PGW, in order to be able to send and receive data, to and from the PDN.

What are call flows?

A call flow is a road map to how calls will be handled from the moment they enter the phone system to the end of the call. Call flows can be used to handle even the most complex call scenarios and enable great customer care.

Why do we need a call flow?

What is call flow in LTE?

LTE Call Flow explained The call flow in the LTE network is unique among mobile communication standards and represents the signaling and sessions established across the network.

What is voice over LTE (VoLTE)?

Voice over LTE (VoLTE) Originating Call Voice over LTE (VoLTE) is the standard for voice call setup in LTE networks. When VoLTE is deployed, phones will not need to fallback to 3G for voice calls. VoLTE uses IMS signaling to setup voice calls. The following VoLTE call flow describes the IMS call setup and release.

What happens when a 4G LTE subscriber initiates a voice call?

Explore contents of messages exchanged during an X2 handover between two eNodeBs. A 4G LTE subscriber initiates a voice call in an LTE network that does not support VoLTE. In such cases, the UE falls back to 3G networks to establish a voice call.

What is CS fallback in LTE?

There are two options of handling voice (CS) call in LTE. CS Fallback is normally done via the existing technology such as WCDMA and GSM where the calls are redirected to legacy networks. For example, if UE wants to make a voice call, the network redirect the call to one of the existing technology like WCDMA or GSM.