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5G SA Handover – Inter gNB-DU and Intra gNB-CU Handover

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The technical details of a 5G Standalone (SA) handover involving inter gNB-DU (gNB Distributed Unit) and intra gNB-CU (gNB Central Unit) handover.

1. Background:

  • 5G SA Architecture:
    • In 5G Standalone mode, the network is entirely based on the 5G architecture, without relying on 4G infrastructure. It consists of gNBs (gNodeB), distributed units (gNB-DU), and central units (gNB-CU).

2. Handover Types:

  • Inter gNB-DU Handover:
    • This type of handover involves the transfer of user equipment (UE) connection from one gNB-DU to another within the same gNB-CU.
  • Intra gNB-CU Handover:
    • This type of handover involves the transfer of UE connection from one gNB-CU to another within the same gNB.

3. Procedure:

Inter gNB-DU Handover:

  • Detection:
    • The decision for inter gNB-DU handover can be based on various factors such as signal strength, load balancing, and quality of service metrics.
  • Measurement Report:
    • The UE periodically sends measurement reports to the serving gNB-CU, including information about neighboring gNB-DUs.
  • Decision Making:
    • The gNB-CU makes a decision to handover based on the measurement reports and network conditions.
  • Handover Request:
    • The serving gNB-CU sends a handover request to the target gNB-DU.
  • Data Forwarding:
    • The target gNB-DU starts receiving and processing data for the UE.
  • Path Switch:
    • The data path is switched from the source gNB-DU to the target gNB-DU.
  • Acknowledgment:
    • Once the handover is complete, acknowledgments are exchanged between the gNB-CU and gNB-DUs.

Intra gNB-CU Handover:

  • Detection:
    • Similar to inter gNB-DU handover, the decision for intra gNB-CU handover is based on network conditions and metrics.
  • Measurement Report:
    • The UE sends measurement reports to the serving gNB-CU, including information about neighboring gNB-CUs.
  • Decision Making:
    • The gNB-CU makes a decision to handover based on the measurement reports and network conditions.
  • Handover Request:
    • The serving gNB-CU sends a handover request to the target gNB-CU.
  • Data Forwarding:
    • The target gNB-CU starts receiving and processing data for the UE.
  • Path Switch:
    • The data path is switched from the source gNB-CU to the target gNB-CU.
  • Acknowledgment:
    • Once the handover is complete, acknowledgments are exchanged between the gNB-CUs.

4. Key Considerations:

  • Latency:
    • Minimizing handover latency is crucial to ensure a seamless user experience.
  • Data Integrity:
    • During handover, mechanisms should be in place to ensure the integrity of data being transferred.
  • Load Balancing:
    • Handovers may be triggered for load balancing purposes to optimize network resources.
  • Security:
    • Security measures must be maintained during the handover process to prevent unauthorized access or data interception.

5. Conclusion:

  • 5G Standalone handovers, whether inter gNB-DU or intra gNB-CU, involve a complex set of procedures to maintain connectivity while optimizing network resources. It requires coordination between different network elements and careful consideration of factors such as latency, data integrity, load balancing, and security.