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5g call flow diagram

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The 5G call flow is a sequence of signaling messages exchanged between different network elements to establish and release a communication session, such as a voice call, video call, or data session, over a 5G network. Below is a high-level overview of the 5G call flow, breaking it down into several phases:

1. Registration and Attach Procedure:

UE (User Equipment) to gNB (Next-Generation NodeB):

  1. Initial Access: The UE performs the initial access by sending a random access preamble to the gNB.
  2. Random Access Response: The gNB responds with a random access response containing the Timing Advance (TA) value.
  3. UE Capabilities and Initial Registration: The UE sends its capabilities and performs the initial registration to the gNB.

gNB to AMF (Access and Mobility Management Function):

  1. Registration Request: The gNB forwards the registration request to the AMF.
  2. Authentication and Security: The AMF initiates the authentication and security procedures with the UE.
  3. Registration Accept: Upon successful authentication, the AMF sends a registration accept message to the gNB.

2. Session Establishment:

UE to AMF:

  1. Service Request: The UE sends a service request to the AMF for establishing a communication session.

AMF to SMF (Session Management Function):

  1. Session Creation Request: The AMF forwards the request to the SMF to create a session.
  2. Policy and Charging Control: The SMF interacts with the PCF (Policy Control Function) and CHF (Charging Function) for policy and charging control decisions.

SMF to UPF (User Plane Function):

  1. Path Establishment: The SMF sets up the data path through the UPF for the user plane data flow.

3. Data Transfer:

  1. Data Transfer: Once the path is established, data packets are transmitted between the UE and the UPF through the gNB and SMF.

4. Session Release:

UE to AMF:

  1. Service Deactivation: The UE sends a service deactivation request to the AMF.

AMF to SMF and UPF:

  1. Session Termination: The AMF initiates the session termination procedure by notifying the SMF and UPF to release resources.

AMF to gNB:

  1. Deregistration Request: The AMF sends a deregistration request to the gNB.

gNB to UE:

  1. RRC Connection Release: The gNB sends an RRC (Radio Resource Control) connection release to the UE.

Key Network Elements Involved:

  • UE (User Equipment): The mobile device or terminal used by the subscriber.
  • gNB (Next-Generation NodeB): The base station in the 5G radio access network (RAN).
  • AMF (Access and Mobility Management Function): The control plane node responsible for mobility management and access control.
  • SMF (Session Management Function): The control plane node responsible for session management.
  • UPF (User Plane Function): The user plane node responsible for data forwarding.