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5g voice call flow

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A 5G voice call flow involves multiple steps and interfaces between different network elements to ensure that a voice call is established, maintained, and terminated properly over a 5G network.

Here's a detailed technical explanation:

1. User Equipment (UE) Initialization:

  • The UE initiates a registration procedure with the 5G Core (5GC) network.
  • The UE sends an initial registration request to the Mobility Management Entity (MME) in the 5GC.

2. 5G Core Network (5GC) Registration:

  • The MME processes the UE's registration request and establishes a session management (SM) context for the UE.
  • The MME then communicates with the Session Management Function (SMF) to set up the data path.

3. Voice Over 5G (Vo5G) Configuration:

  • The UE and the 5GC establish parameters and configurations for Vo5G.
  • This involves setting up Quality of Service (QoS) parameters specific to voice services.

4. Establishment of Radio Bearer for Voice:

  • The UE and the gNodeB (gNB) establish a Radio Bearer specifically dedicated to voice traffic.
  • This bearer ensures that the necessary resources are allocated for the voice call.

5. Voice Service Setup:

  • The SMF communicates with the Policy Control Function (PCF) to ensure the correct policy and charging rules are applied for the voice service.
  • The PCF authorizes and sets up the necessary policies for the voice session.

6. Voice Call Initiation:

  • Once the necessary configurations and bearers are in place, the UE initiates a voice call.
  • The voice call setup message is sent towards the 5GC, indicating the call's details.

7. 5G Core Network Routing:

  • The 5GC routes the voice call towards the appropriate destination, which might be another 5G device or a device on a different network (e.g., 4G, VoLTE, PSTN).

8. Interworking:

  • If the call is destined for a device on a different network (like 4G or PSTN), the 5GC communicates with the appropriate gateway (e.g., IMS gateway, PSTN gateway) for interworking.

9. Media Establishment:

  • Once the call is routed, the necessary media resources are allocated for voice transmission.
  • This involves setting up media streams and ensuring the proper codecs and configurations are used for voice encoding and decoding.

10. Call Handling & Control:

  • During the call, the 5GC handles call control functions, including call hold, call transfer, and other supplementary services.
  • The 5GC also monitors the call quality and can make dynamic adjustments if needed, based on the network conditions.

11. Call Termination:

  • When the call ends, the 5GC releases the resources allocated for the voice call.
  • The session management context is terminated, and any associated bearers are released.
  • The UE sends a deregistration or detachment request to the 5GC if it wishes to detach from the network.