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registration call flow in 5g

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The registration call flow in 5G involves several steps for a user device (UE - User Equipment) to establish a connection with the 5G network. Here's a detailed technical explanation of the registration call flow in 5G:

  1. Attach Request (Initial Registration):
    • The UE initiates the registration process by sending an Attach Request to the 5G Core (5GC). This is typically triggered when the UE is powered on or enters a new service area.
  2. Authentication and Security Setup:
    • The 5G Core authenticates the UE using the Authentication Center (AUSF) and establishes security keys for the communication session. This involves the use of the Authentication Vector and the derivation of keys like the NAS (Non-Access Stratum) keys.
  3. Authorization:
    • The UE is then authorized to access the network. This step involves checking the user's subscription information, policy control, and charging rules.
  4. Initial Registration in the Access Network:
    • The UE then registers with the 5G Access Network (gNB - Next-Generation NodeB). This includes procedures like Random Access Channel (RACH) procedures for attaching to the network.
  5. PDU Session Establishment:
    • The next step is the establishment of the Packet Data Unit (PDU) session. The UE requests the establishment of a PDU session to enable data transfer. This involves setting up the necessary bearers and obtaining IP addresses.
  6. Registration with the Session Management Function (SMF):
    • The UE registers with the SMF, and the SMF becomes aware of the UE's presence and its connectivity requirements.
  7. Mobility Management (AMF):
    • The Access and Mobility Management Function (AMF) handles the mobility of the UE within the network. It manages the UE context, including tracking area updates.
  8. User Plane Establishment:
    • The user plane is established to enable the actual data transfer. This involves setting up the necessary tunnels and paths for the data to flow between the UE and the external network.
  9. Finalize Attach Procedure:
    • The 5G Core finalizes the attach procedure, acknowledging the successful registration of the UE in the network.
  10. Update Location:
    • The location of the UE is updated in the Home Subscriber Server (HSS) to reflect its current service area.
  11. Handover (Optional):
    • If the UE is in motion, handover procedures might be initiated to transfer the connection seamlessly between different gNBs or even different NG-RAN nodes.

It's important to note that the above steps represent a simplified overview, and there might be additional details and variations depending on the specific deployment scenario and the network architecture in use. The 5G registration call flow is designed to ensure secure and efficient connectivity for the UE within the 5G network.