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xn handover call flow

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It seems like there might be a slight confusion or typo in your request. It appears you are referring to "XN Handover" or "Xn Interface Handover" in the context of telecommunications, specifically in the 5G network architecture. However, the term "xn" is typically associated with the interface between two 5G base stations (gNBs) in the 5G New Radio (NR) architecture.

Assuming you are indeed referring to the Xn handover call flow in 5G, let's delve into the technical details:

5G Xn Interface Handover Call Flow:

1. Preparation Phase:

  • Context Establishment:
    • Before a handover occurs, neighboring gNBs exchange information about the radio environment, capabilities, and resource availability through the Xn interface.
    • Context information for the user equipment (UE) is shared between the source and target gNBs.

2. Triggering Handover:

  • Event Trigger:
    • Handovers can be triggered by various events, such as the deterioration of the radio link quality or load balancing considerations.
    • The decision to handover is typically made by the source gNB based on measurements and network policies.

3. Handover Request:

  • Handover Command:
    • The source gNB initiates the handover process by sending a Handover Required message to the target gNB over the Xn interface.
    • This message includes information about the UE, the reason for handover, and the suggested target cell.

4. Target gNB Preparation:

  • Resource Allocation:
    • The target gNB evaluates its resources, confirms the availability of necessary radio resources, and prepares for the handover.
    • It may allocate radio resources and configure the necessary parameters for the UE.

5. Handover Execution:

  • UE Configuration:
    • The target gNB sends a Handover Request Acknowledge message to the source gNB, indicating its readiness for the handover.
    • The source gNB instructs the UE to reconfigure its radio connection parameters for the target cell.

6. Data Forwarding:

  • Data Path Switch:
    • The source gNB starts forwarding the user data to the target gNB through the Xn interface.
    • This ensures a seamless transfer of data from the source cell to the target cell without disruption.

7. Handover Completion:

  • Data Path Switch Confirmation:
    • The target gNB confirms the successful handover completion to the source gNB through the Handover Request Acknowledge message.
    • The source gNB releases the resources associated with the UE in the source cell.

8. Post-Handover Optimization:

  • Optimization and Verification:
    • The network may perform optimization procedures, such as updating neighbor lists and adjusting radio parameters, to ensure optimal UE performance in the new cell.

This call flow describes a simplified version of the Xn handover process in 5G. The Xn interface plays a crucial role in facilitating communication between gNBs during the handover procedure, ensuring a smooth transition of the UE's connection from the source to the target cell. The detailed specifications and procedures may vary based on the specific 5G network deployment and standards implemented by the network operator.