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volte fallback

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Voice over LTE (VoLTE) Fallback refers to the process by which a voice call using Voice over LTE (VoLTE) technology is handed over or "fallen back" to a circuit-switched network (2G/3G) when certain conditions are not met for a VoLTE call to be established or maintained. VoLTE Fallback is designed to ensure that users can make and receive voice calls even in areas where LTE (4G) coverage may be limited or unavailable.

Here's a technical breakdown of the VoLTE Fallback process:

  1. VoLTE Call Attempt:
    • When a user initiates a voice call, the device first attempts to set up the call using VoLTE.
    • VoLTE uses IP (Internet Protocol) networks for voice communication, providing higher quality audio and faster call setup times compared to traditional circuit-switched voice calls.
  2. VoLTE Preconditions:
    • VoLTE requires certain preconditions to be met for a call to be established successfully. These preconditions include sufficient LTE coverage, VoLTE support in both the caller and receiver devices, and network support for VoLTE.
  3. Fallback Triggering Conditions:
    • If the preconditions for VoLTE are not met, the network triggers a fallback mechanism. Fallback can be triggered due to reasons such as insufficient LTE coverage, lack of VoLTE support in the devices, or network-specific policies.
  4. Network Decision and Paging:
    • The network decides that a fallback is necessary, and it initiates a paging procedure to locate the user equipment (UE) in the circuit-switched network (2G/3G).
  5. UE Response:
    • The user equipment (UE), which is the mobile device, responds to the paging request from the circuit-switched network.
  6. Handover to Circuit-Switched Network:
    • Once the UE is located, the call is handed over from the LTE network to the circuit-switched network. The handover may involve a change in the radio access technology (RAT) from LTE to 2G or 3G.
  7. Circuit-Switched Call Setup:
    • The circuit-switched call is then set up using traditional methods, and the voice call proceeds over the 2G or 3G network.
  8. VoLTE Fallback Completion:
    • The voice call continues to be serviced over the circuit-switched network until the end of the call.
  9. Return to VoLTE:
    • Once the call is completed or when VoLTE conditions are again met, the network may initiate a handover back to VoLTE for subsequent calls.

It's essential to note that VoLTE Fallback is a transitional mechanism to ensure voice service continuity when VoLTE is not feasible. As network infrastructure improves and VoLTE support becomes more widespread, the reliance on fallback mechanisms is expected to decrease over time.