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volte srvcc

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Voice over LTE (VoLTE) is a technology that allows voice calls to be made over an LTE (Long-Term Evolution) network, which is the standard for wireless broadband communication. VoLTE offers higher quality voice calls and faster call setup times compared to traditional circuit-switched voice services.

VoLTE Basics:

  1. VoLTE Call Setup:
    • VoLTE calls are established using IP-based protocols over the LTE network.
    • The voice data is packetized and transmitted as data packets over the LTE network.
  2. SRVCC Overview:
    • Single Radio Voice Call Continuity (SRVCC) is a technology that enables a smooth handover of voice calls from LTE to legacy circuit-switched networks (2G/3G) without interrupting the call.

SRVCC Process:

  1. Triggering Conditions:
    • SRVCC is typically triggered when a VoLTE user moves out of LTE coverage and into an area where only 2G/3G is available.
    • It can also be triggered due to other factors like network congestion, radio link failure, or handover failure.
  2. eSRVCC (Enhanced SRVCC):
    • There is an enhanced version called eSRVCC that allows for a more efficient handover process.
    • eSRVCC uses IP Multimedia Subsystem (IMS) and Session Initiation Protocol (SIP) for signaling.
  3. Handover Preparation:
    • Before the handover, the LTE network prepares the call for transition by establishing a connection with the circuit-switched network.
  4. Media Anchoring:
    • The media (voice) is anchored in the LTE network until the handover is completed.
    • This ensures that the voice quality is maintained during the handover process.
  5. Handover Execution:
    • The control plane signaling is handed over first to the circuit-switched network.
    • The user plane (voice traffic) is then redirected to the legacy network.
  6. Completion of Handover:
    • Once the handover is complete, the voice call continues on the legacy network seamlessly.
    • The LTE resources are released, and the call is now handled by the circuit-switched network.
  7. End of Call:
    • When the call is terminated, the LTE network is notified, and any remaining resources are released.

Benefits of SRVCC:

  1. Call Continuity:
    • SRVCC ensures that voice calls can continue without interruption even when moving between LTE and non-LTE coverage areas.
  2. Enhanced User Experience:
    • Users experience seamless voice call handovers, providing a more reliable and consistent service.
  3. Interoperability:
    • SRVCC facilitates interoperability between LTE and legacy circuit-switched networks, allowing for a smooth transition as networks evolve.