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vowifi call flow architecture

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VoWiFi (Voice over Wi-Fi) allows users to make voice calls using a Wi-Fi connection instead of a traditional cellular connection. The VoWiFi call flow involves several components and steps to ensure that the call is established and maintained. Here's a technical breakdown of the VoWiFi call flow architecture:

1. Device Initiation:

  • User Action: The user initiates a voice call from their VoWiFi-enabled device (e.g., smartphone).
  • Wi-Fi Association: The device connects to a Wi-Fi network, which can be public or private (e.g., home Wi-Fi, public hotspot).

2. Authentication & Registration:

  • EAP Authentication: The device uses Extensible Authentication Protocol (EAP) methods to authenticate itself with the Wi-Fi network. This can involve methods like EAP-TLS, EAP-TTLS, or EAP-SIM for securely transmitting credentials.
  • Network Authentication: Once connected, the device may need to authenticate with the VoWiFi service provider's network using protocols like SIP (Session Initiation Protocol) or Diameter.

3. Address Resolution & Routing:

  • DNS Lookup: The device performs a Domain Name System (DNS) lookup to resolve the SIP domain name associated with the dialed number.
  • Proxy Server Identification: Based on DNS results, the device identifies the appropriate SIP proxy server for routing the call.

4. Call Establishment:

  • SIP INVITE: The device sends a SIP INVITE message to the identified proxy server, indicating the intent to establish a voice call.
  • Proxy Server Processing: The SIP proxy server processes the INVITE message, performs call routing, and may involve other components like a Session Border Controller (SBC) for security and interworking.
  • Authentication & Authorization: The proxy server may authenticate the user and authorize the call based on policies and user profiles.

5. Media Negotiation & Setup:

  • SDP Exchange: Using the Session Description Protocol (SDP) within SIP, both parties negotiate the media parameters (e.g., codec, bitrate) for the voice call.
  • NAT Traversal: If the device is behind a Network Address Translation (NAT) device, mechanisms like STUN (Session Traversal Utilities for NAT) or TURN (Traversal Using Relays around NAT) may be used to establish media paths.

6. Call Handling & Quality:

  • Call Control: Once media paths are established, the SIP proxy server or other components handle call control functions like call hold, transfer, or termination.
  • Quality Monitoring: Throughout the call, Quality of Service (QoS) mechanisms may be applied to monitor and ensure a satisfactory voice quality over the Wi-Fi network.

7. Call Termination:

  • Call Completion: When the call ends, signaling messages (e.g., SIP BYE) are exchanged between the devices and network components to terminate the call.
  • Resource Release: Resources allocated for the call (e.g., media channels, session states) are released, ensuring efficient use of network resources.

Components Involved:

  • VoWiFi-enabled Devices: Devices capable of supporting VoWiFi functionality.
  • Wi-Fi Network: Provides the wireless connectivity for VoWiFi calls.
  • SIP Proxy Server: Routes SIP signaling messages and handles call control functions.
  • Session Border Controller (SBC): Provides security, interworking, and policy enforcement for VoWiFi calls.
  • Authentication Server: Manages user authentication and authorization processes.
  • Media Servers: Handle media processing tasks like transcoding, conferencing, or recording if required.