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vowifi to volte handover call flow

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Voice over Wi-Fi (VoWiFi) to Voice over LTE (VoLTE) handover is a process that allows seamless transition of a voice call from a Wi-Fi network to an LTE (4G) network, or vice versa. This handover is designed to ensure continuity of the voice call while optimizing the network resources. Let's break down the technical details of the VoWiFi to VoLTE handover call flow:

  1. VoWiFi Call Establishment:
    • The call starts over a Wi-Fi network using VoWiFi technology. The mobile device connects to the Wi-Fi network and establishes a VoWiFi call using the IP Multimedia Subsystem (IMS) architecture.
  2. Quality of Service Monitoring:
    • Quality of Service (QoS) parameters, such as signal strength, latency, and jitter, are continuously monitored during the VoWiFi call. The device constantly evaluates the conditions of the Wi-Fi network.
  3. Trigger for Handover:
    • Various triggers can initiate the handover process. Common triggers include deteriorating Wi-Fi signal quality, loss of Wi-Fi connection, or a predefined policy to switch to VoLTE based on network conditions.
  4. Handover Decision:
    • The decision to hand over the call to VoLTE is made by the device or the network, based on the predefined policy and network conditions. If the Wi-Fi conditions are no longer optimal, the device decides to hand over the call to VoLTE.
  5. VoLTE Session Establishment:
    • Once the decision is made, the device initiates a request to establish a VoLTE session. This involves authenticating the user and setting up the necessary parameters for the voice call on the LTE network.
  6. Bearer Setup:
    • Bearer setup involves establishing a data communication path for the voice call on the LTE network. This includes allocating resources and configuring the necessary parameters for the call.
  7. Handover Execution:
    • The actual handover process takes place. The call is seamlessly transferred from the VoWiFi network to the VoLTE network. The transition is designed to be imperceptible to the user, ensuring a smooth and uninterrupted voice communication experience.
  8. Data Forwarding:
    • As the handover occurs, data packets carrying the voice call are forwarded from the Wi-Fi network to the LTE network. This is a critical step in ensuring continuity and minimizing any disruption in the call.
  9. Call Continuity:
    • The user continues the voice call over the LTE network without experiencing any noticeable interruption. The handover process is transparent, and the call quality is maintained throughout the transition.
  10. VoLTE Call Termination:
    • When the call is completed, the VoLTE session is terminated, and the device may revert to the VoWiFi network if it provides better conditions for subsequent calls.