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Handover From E-UTRA Failure

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Handover From E-UTRA Failure is a technical procedure in mobile communication networks, particularly in LTE (Long-Term Evolution), that occurs when a handover from the E-UTRA (Evolved Universal Terrestrial Radio Access) network to another radio access technology (RAT) or external network is unsuccessful. This procedure involves the network and the User Equipment (UE) detecting and managing the failure to ensure service continuity. Here's a detailed technical explanation of the Handover From E-UTRA Failure procedure:

1. Handover Trigger and Initiation:

  • The Handover From E-UTRA Failure procedure is triggered when the network initiates a handover from the LTE (E-UTRA) network to another RAT or external network.
  • The handover decision may be made due to reasons such as network optimization, load balancing, or the UE moving out of LTE coverage.

2. Handover Request and Execution:

  • The network initiates the handover by sending a "Handover From E-UTRA Request" message to the UE. This message contains instructions for the UE to perform the handover.
  • The UE follows the instructions and attempts to switch to the target RAT or external network.

3. Handover Failure Detection:

  • During or after the handover process, if any issues prevent the successful completion of the handover, the UE and the network detect the failure.
  • The network may identify the failure through a lack of expected response from the UE or by monitoring handover-related events.

4. Failure Cause Analysis:

  • Both the UE and the network analyze the cause of the handover failure. Common causes can include:
  • Poor signal quality in the target RAT or external network.
  • Authentication or security issues.
  • Resource unavailability in the target network.
  • UE-related issues such as inability to decode target network signals.

5. Handover Failure Handling:

  • Depending on the cause of the failure, the network and the UE may take specific actions to address the issue:
  • Retrying the Handover: If the failure was due to temporary conditions, the network may attempt to retry the handover.
  • Network Reconfiguration: The network may adjust its handover parameters or configuration to improve the chances of a successful handover.
  • UE Reconfiguration: The UE may receive instructions to change its handover-related settings or parameters.
  • Reporting: The UE may send measurement reports to the network to provide feedback on the failure.

6. Service Continuity:

  • During and after the handover failure recovery attempts, the UE may continue to use the LTE network for communication.
  • Service continuity is maintained in LTE until the handover is successfully completed or alternative actions are taken.

7. Procedure Completion:

  • The Handover From E-UTRA Failure procedure is considered complete when one of the following conditions is met:
  • The handover is successfully retried, and the UE switches to the target RAT or external network.
  • The network and the UE determine that the handover cannot be successfully completed, and alternative actions are taken (e.g., instructing the UE to remain in LTE, initiating a different handover).

This procedure is essential for ensuring that service continuity is maintained even in cases where a handover from LTE to another network is initially unsuccessful. By detecting and addressing handover failures, the network can ensure that UEs continue to receive services without disruption.