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nr call flow

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The term "NR call flow" typically refers to the call flow in a 5G (New Radio) network. NR is the air interface standard for 5G wireless communication, and understanding the call flow involves the series of steps and messages exchanged between different network entities during the establishment and release of a call or data session. The NR call flow can be complex, involving various protocols and procedures. Below is a high-level technical explanation of the NR call flow:

  1. UE (User Equipment) Initialization:
    • The process begins with the UE powering on and initializing its radio capabilities.
    • The UE performs initial access procedures, including cell search, synchronization, and random access, to connect to the network.
  2. PLMN Selection and Registration:
    • The UE selects a Public Land Mobile Network (PLMN) and registers with it.
    • The UE sends a Registration Request to the selected PLMN.
  3. Initial Attach:
    • The UE performs the initial attach procedure, where it establishes a connection with the 5G Core (5GC) network.
    • The UE sends an Initial Registration Request to the 5GC.
  4. Access and Mobility Management (AMF) Registration:
    • The AMF (Access and Mobility Management Function) handles the registration and mobility management for the UE.
    • The UE registers with the AMF, and the AMF allocates necessary resources.
  5. Authentication and Security Setup:
    • The UE undergoes authentication with the Home Subscriber Server (HSS) or Authentication Server (AUSF).
    • Security keys are exchanged between the UE and the network to establish a secure communication channel.
  6. PDU (Protocol Data Unit) Session Establishment:
    • The UE requests the establishment of a PDU session, which is a data communication session, from the 5GC.
    • The 5GC processes the request and allocates resources for the PDU session.
  7. Bearer Setup:
    • The bearer setup involves the establishment of radio bearers for data transfer between the UE and the gNB (gNodeB).
    • Radio bearers are configured to ensure efficient data transfer.
  8. Data Transfer:
    • Once the bearers are set up, data transfer can occur between the UE and the network.
    • The user can engage in services like internet browsing, video streaming, etc.
  9. Call Handover (Optional):
    • If the UE moves to an area served by a different gNB, a handover procedure may be initiated to maintain the ongoing call.
  10. PDU Session Release:
    • When the UE concludes its communication, it may request the release of the PDU session.
  11. Detach:
    • The UE can detach from the network when it is done using services, or it may detach during power-off.