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What is CSFB redirection?

What is CSFB redirection?

For redirection-based CSFB, UE initiates call setup from RACH. For handover-based CSFB, UE establish call in 4G LTE, and then performs handovers to 3G. Handover-based CSFB would deliver higher call setup reliability than redirection. The reason is that network provides higher priority to handover than initial call.

What is blind CSFB?

Blind CSFB: This is the most common type of CSFB implementation where the eNB will send the UE blindly to 3G/2G. This type of implementation usually has more reliability but the delay is higher in call setup because the UE takes around 500 to 700 milliseconds to complete the measurement of the target CS RAT.

What is CSFB in 4G?

Circuit Switched Fallback (CSFB), with the help of a global system for mobile communication (GSM) or another circuit-switched network, delivers voice and SMS services to LTE devices. The necessity for a Circuit Switch FallBack for the packet-based all-IP network, LTE, which cannot support circuit-switched calls.

Why CSFB is required?

LTE is an all-IP technology and therefore cannot transport switched services such as voice or SMS, so CSFB is needed. When an LTE device is used to make or receive a voice call or SMS, the device “falls back” to the 3G or 2G network to complete the call or to deliver the SMS text message.

How CSFB is triggered?

To support voice and other CS services CS Fallback was introduced. Simply speaking, when a UE or mobile phone starts a voice call the network move the UE to a legacy UMTS (3G) or GSM (2G) network. The UE use the legacy network to initiate the call and complete the call.

What is difference between CSFB and VoLTE?

CSFB vs VoLTE​ CSFB (Circuit Switch Fallback) is a technology that supports voice and SMS services in 4G networks using the 2G/3G systems. VoLTE (Voice over LTE), on the other hand, means that a call is made through a 4G network (Making calls over IP).

What is CSFB in 5G?

With respect to LTE, if CSFB (Circuit Switched Fallback) is in use, the device will fall back from the LTE network to make or receive a call on 2G/3G. Conversely, if the LTE network supports VoLTE (Voice over LTE), the call will remain on LTE, with call control being supplied by an IMS (IP Multimedia Subsystem).

What is CSFB in 5g?

How does LTE call work?

As the name suggests, Voice over LTE happens when your carrier allows you to place a phone call over your LTE connection instead of the older legacy voice networks. For example, Verizon Wireless traditionally used 1XRTT for all of your voice calls, relying on LTE for data.

What is a CS call?

With Circuit-Switched or CS, a dedicated circuit is engaged for the entire duration of a conversation between two users. The circuit-switched technology is a highly reliable way of ensuring Quality of Service (QoS) for voice calls.

Which is the best way to implement CSFB?

There are several different ways to implement CSFB (CS Fallback) and one of the most common way is to use ‘Redirection’ method. For the details of ‘Redirection’ mechanism, refer to ‘Redirection’section. Reference [1]

Can a CSFB be based on a handover?

Over here, the CSFB can also be based on handover in which case, the eNB will initiate a handover to the target RAT’s cell and send the UE to that specific cell for which the MR has been generated by the UE.

What happens when CSFB is not turned on?

If CSFB is not enabled in the network, the incoming voice calls will fail, however outgoing voice calls can still work depending on the mobile. However, let’s start from the basics to understand this in detail. The figure explains an incoming CSFB call when the UE is in idle mode.

How does UE prepare for CSFB call flow?

In response to this the UE sends the Extend Service Request message. In this message it mention the service type as “mobile terminating CS fallback”. Also, it sets that the CSFB request is accepted by the UE. After receiving this message, the UE prepares itself for CSFB procedure. It starts the timer T3417.