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5g pdu session establishment call flow

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The establishment of a 5G PDU (Packet Data Unit) session involves several steps and messages exchanged between the User Equipment (UE), the gNB (5G New Radio Base Station), and the 5G Core (5GC). Below is a simplified overview of the 5G PDU session establishment call flow:

  1. UE Attachment to the 5G Network:
    • The UE attaches to the 5G network by connecting to a gNB.
    • The UE initiates the Registration procedure with the 5G Core Network (5GC).
  2. Registration Request:
    • The UE sends a Registration Request to the 5GC.
  3. Access and Mobility Management (AMF) Registration Accept:
    • The AMF (Access and Mobility Management Function) in the 5GC processes the Registration Request and sends a Registration Accept message to the UE.
  4. Authentication and Security Setup:
    • The UE and the 5GC perform authentication and establish security keys.
    • The AMF generates a NAS (Non-Access Stratum) Security Mode Command, and the UE responds with a NAS Security Mode Complete message.
  5. Establishment of a PDU Session:
    • The UE initiates the PDU Session Establishment procedure by sending a PDU Session Establishment Request to the 5GC.
  6. AMF PDU Session Establishment Accept:
    • The AMF processes the PDU Session Establishment Request and sends a PDU Session Establishment Accept to the UE.
  7. gNB Configuration:
    • The AMF informs the gNB about the establishment of the PDU session, and the gNB configures the necessary radio resources.
  8. UE PDU Session Establishment Complete:
    • The UE responds with a PDU Session Establishment Complete message after completing the necessary procedures.
  9. Data Transfer:
    • With the PDU session established, data transfer can begin between the UE and the network.

It's important to note that this is a simplified overview, and the actual call flow may involve additional signaling messages and procedures for features like Quality of Service (QoS) setup, policy enforcement, and mobility management. The specifications for 5G are defined by 3GPP (3rd Generation Partnership Project), and detailed information can be found in their technical documents, specifically in the 5G specifications (e.g., TS 23.501 for System Architecture and TS 38.300 for NR).