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NR-IRAT Handover From UTRAN Failure

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In 5G New Radio (NR), an NR-IRAT (Inter-RAT) Handover From UTRAN (Universal Terrestrial Radio Access Network) Failure refers to a scenario in which the handover process from a UTRAN network (3G) to a 5G NR (New Radio) network encounters difficulties or fails to complete successfully. This can happen due to various reasons, and the failure triggers specific signaling and procedures to handle the situation. Here's a technical explanation of NR-IRAT Handover From UTRAN Failure:

1. Purpose of NR-IRAT Handover From UTRAN Failure Handling:

  • The primary purpose of handling NR-IRAT Handover From UTRAN Failure is to manage the situation when a UE (User Equipment) cannot successfully transition from a UTRAN network to a 5G NR network.
  • This failure may occur due to factors like poor signal quality, network congestion, or incompatible network configurations.

2. Handover Scenario:

  • The handover scenario involves a UE that is initially connected to a UTRAN network and needs to transition to a 5G NR network, either for improved service quality or for accessing 5G-specific services.

3. UE's Handover Request:

  • The UE initiates the handover process by sending a handover request message, indicating its intention to move from the UTRAN to a 5G NR cell.
  • This request typically includes information about the target 5G NR cell.

4. UTRAN's Response:

  • Upon receiving the UE's handover request, the UTRAN network processes the request and assesses the feasibility of the handover.
  • If the UTRAN determines that the handover cannot be executed successfully, it may generate the NR-IRAT Handover From UTRAN Failure message.

5. Contents of NR-IRAT Handover From UTRAN Failure Message:

  • The NR-IRAT Handover From UTRAN Failure message contains critical information, including:
  • Indication of the handover failure.
  • A specific failure cause or reason for the failure, which may include details about why the handover could not proceed.
  • Optionally, recommendations or additional information for the UE to address the failure.

6. UE Reaction to Handover Failure:

  • Upon receiving the NR-IRAT Handover From UTRAN Failure message, the UE reacts according to the cause provided in the message.
  • Possible reactions include attempting a handover to another cell (if available), initiating reselection to another cell, or staying connected to the current UTRAN cell.

7. Retries and Recovery Procedures:

  • Depending on the cause of the failure, the UE may make additional handover attempts or reselection attempts to find a suitable 5G NR cell.
  • Recovery procedures may also include reconfiguring radio parameters or adapting to network conditions.

8. Quality of Service (QoS) Considerations:

  • The NR-IRAT handover failure may impact the QoS for the UE, as the desired transition to 5G NR may not have been achieved.
  • The UE and network may need to take actions to ensure that the user's service continuity is maintained at an acceptable level.

In summary, the NR-IRAT Handover From UTRAN Failure handling is a procedure that manages situations where a handover from a UTRAN (3G) network to a 5G NR network cannot be successfully completed. The handling involves signaling between the UE and the UTRAN, and it provides information about the cause of the failure. The UE may then take appropriate actions to address the failure and potentially make additional handover attempts or reselections to establish a successful connection in the 5G NR network.