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NR-Handover From E-UTRA Request

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In 5G New Radio (NR) networks, the "NR-Handover from E-UTRA Request" procedure is a technical process that initiates a handover (also known as a handoff) of a User Equipment (UE) from a 4G LTE (E-UTRA) cell to a 5G NR cell. This procedure is part of mobility management in a dual-connectivity scenario where the UE simultaneously connects to both LTE and NR networks for data transfer. Below is a detailed technical explanation of the NR-Handover from E-UTRA Request procedure:

Background: Dual-Connectivity:

  • Dual-connectivity is a network architecture where a UE is simultaneously connected to LTE (E-UTRA) and 5G NR cells. This is often used to provide seamless mobility and enhanced data rates as the UE moves between LTE and NR coverage areas.

UE Mobility and Measurement:

  1. As the UE moves within the network, it continuously measures the radio conditions, including signal strength, signal quality, and interference levels, for both LTE and NR cells.
  2. The UE determines that there is an opportunity for handover from the LTE (E-UTRA) cell to a more suitable NR cell based on the measurement reports.

Handover Trigger:

  1. The UE sends a handover request to the LTE (E-UTRA) cell, indicating its intention to perform a handover to the 5G NR cell. This request includes information about the target NR cell and the requested handover.
  2. The LTE (E-UTRA) cell evaluates the handover request and, if conditions are met, proceeds with the handover preparation.

NR Cell Selection and Preparation:

  1. The LTE (E-UTRA) cell selects an appropriate NR cell as the target for handover. This decision is typically based on factors such as signal quality, interference levels, and network load.
  2. The LTE (E-UTRA) cell initiates handover preparation activities with the target NR cell. This may involve signaling and resource allocation in the NR cell.

Handover Command to UE:

  1. Once the handover preparations are complete, the LTE (E-UTRA) cell sends a handover command to the UE, instructing it to perform the handover to the target NR cell.
  2. The handover command includes information about the target NR cell and any specific instructions for the handover process.

UE Transition to NR Cell:

  1. The UE configures its radio resources to communicate with the target NR cell, including setting up physical channels, allocating radio bearers, and configuring Quality of Service (QoS) parameters.
  2. The UE initiates data transfer through the target NR cell, ensuring continuity of service during the handover process.

Handover Confirmation:

  1. The UE acknowledges the handover by sending a handover confirmation message to the LTE (E-UTRA) cell. This confirms that the UE has successfully switched to the target NR cell.
  2. The LTE (E-UTRA) cell may acknowledge the handover confirmation, ensuring that both the UE and the network are aware of the successful handover.

Release of LTE Resources:

  1. After confirming the successful handover, the LTE (E-UTRA) cell releases the radio resources that were allocated to the UE for LTE communication, freeing them up for other users.

Normal Operation in NR Cell:

  1. The UE and the target NR cell are now in normal operation, and the UE continues to monitor the network for any future handover opportunities or changes in serving cells.

The NR-Handover from E-UTRA Request procedure is a key aspect of mobility management in dual-connectivity scenarios, ensuring that UEs can seamlessly transition between LTE and NR cells to maintain connectivity and optimize network resource utilization. The procedure's complexity and specific parameters can vary depending on network configurations and the mobility management strategies in place.