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Handover From E-UTRA Request

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The "Handover From E-UTRA Request" is a technical procedure in mobile communication networks like LTE (Long-Term Evolution) that initiates a handover from the E-UTRA (Evolved Universal Terrestrial Radio Access) network to another radio access technology (RAT) or an external network. This procedure is part of the mobility management functions and is used when the network decides to move a User Equipment (UE) from LTE to another network, such as UMTS (Universal Mobile Telecommunications System) or a non-3GPP network. Here's a detailed technical explanation of the "Handover From E-UTRA Request" procedure:

1. Triggering Event:

  • The "Handover From E-UTRA Request" procedure is triggered by specific network conditions or requirements. Common triggers include:
  • Coverage Change: The UE is moving out of LTE coverage, and the network needs to hand it over to another RAT for continuous service.
  • Load Balancing: The network may decide to offload some UEs to other RATs to balance the load on the LTE network.
  • Inter-RAT Mobility: The UE may be required to switch to a different RAT due to better signal quality or specific service requirements.

2. Handover Decision:

  • The network entity responsible for mobility management, such as the Mobility Management Entity (MME) in LTE, makes a decision to initiate a handover based on network policies and measurement reports from the UE.
  • The network determines the target RAT or network to which the UE should be handed over.

3. Handover Request Generation:

  • The network generates a "Handover From E-UTRA Request" message, which includes instructions for the UE to perform the handover.
  • This message typically includes information such as:
  • The target RAT or network identifier.
  • Handover type (e.g., Inter-RAT handover).
  • Parameters for radio resource configuration in the target RAT or network.
  • Security-related information to protect the message.

4. Transmission to the UE:

  • The "Handover From E-UTRA Request" message is transmitted from the network to the UE over the LTE radio interface.
  • The UE receives the message and processes the instructions.

5. UE Preparation:

  • The UE prepares for the handover by configuring its radio interface according to the instructions provided in the message.
  • It may also perform measurements on the target RAT or network to assess the suitability of the handover.

6. Handover Execution:

  • At the appropriate time, the UE initiates the handover by switching to the target RAT or network as instructed.
  • This involves performing necessary radio link synchronization and adjustments to establish a connection in the new network.

7. Measurement Report and Handover Complete:

  • After the handover is complete, the UE generates a measurement report indicating its success or failure in connecting to the new RAT or network.
  • If successful, the UE may send a "Handover From E-UTRA Complete" message to the network to inform it of the successful handover.

8. Service Resumption:

  • Once the handover is successfully completed, the UE resumes its services, and data transfer continues in the new RAT or network.

9. Procedure Completion:

  • The "Handover From E-UTRA Request" procedure is considered complete when the UE has successfully handed over to the target RAT or network, and communication services are restored.

This procedure is crucial for ensuring that UEs maintain connectivity and service continuity when transitioning between different radio access technologies or networks, such as LTE to UMTS or LTE to Wi-Fi. It allows for efficient network resource management and optimization.