Handover Request Acknowledge

The Handover Request Acknowledge is a technical procedure in mobile telecommunications networks, particularly in the context of 4G LTE (Long-Term Evolution) and 5G networks. It occurs when a mobile user equipment (UE) initiates a handover request, and the network acknowledges the request. Handovers are essential for maintaining seamless communication as a UE moves between different cells within the network. Below is a technical explanation of the Handover Request Acknowledge procedure:

1. Handover Trigger:

• UE Movement: The handover procedure is initiated when a UE, while in an active communication session, moves from one cell to another. This movement may be due to factors like signal strength, network optimization, or load balancing.

2. Handover Preparation:

• Network Assessment: The network evaluates the UE's movement and determines the target cell to which the UE should be handed over.
• Resource Allocation: Resources, including radio bearers, are allocated in the target cell to accommodate the incoming UE.

3. Handover Request from UE:

• UE Initiates Handover: The UE realizes it needs to switch to a new cell and initiates a Handover Request. This request is typically sent to the source cell's eNodeB (in LTE) or gNodeB (in 5G).

4. Source Cell Processing:

• Message Handling: The source cell's eNodeB/gNodeB receives the Handover Request message from the UE and processes it.
• Verification: The source cell verifies the request's validity and ensures that the UE is allowed to perform a handover.

5. Handover Request Forwarding:

• Target Cell Selection: Based on network algorithms and assessment, the source cell selects a target cell (another eNodeB or gNodeB) to which the UE should be handed over.
• Forwarding to Target Cell: The source cell forwards the Handover Request to the target cell, indicating that the UE wishes to move to the new cell.

6. Target Cell Processing:

• Message Reception: The target cell's eNodeB/gNodeB receives the forwarded Handover Request from the source cell and processes it.
• Resource Availability: The target cell verifies that it has sufficient resources and capacity to accommodate the UE.

7. Handover Decision:

• Decision in Target Cell: Based on its own assessment and resource availability, the target cell decides whether to accept or reject the handover request.
• Handover Parameters: If accepted, the target cell configures the necessary handover parameters and prepares for the UE's arrival.

8. Handover Request Acknowledge Generation:

• Positive Acknowledgment: If the target cell accepts the handover request, it generates a Handover Request Acknowledge message.
• Message Contents: The acknowledgment typically includes information about the handover procedure, such as new radio parameters and handover preparation details.

9. Message Signaling:

• Response to Source Cell: The Handover Request Acknowledge message is sent back to the source cell, which will relay it to the UE.

10. Source Cell Handling:

• Message Relay: The source cell's eNodeB/gNodeB receives the Handover Request Acknowledge message from the target cell and relays it to the UE.

11. UE Processing:

• Message Reception: The UE receives the Handover Request Acknowledge message and processes it.
• Context Preparation: The UE prepares its radio context for handover to the target cell.

12. Handover Execution:

• UE Handover: The UE switches its connection from the source cell to the target cell, and communication continues seamlessly in the new cell.

13. Handover Completion:

• Confirmation: The source cell confirms the handover completion to the core network.
• Service Continuation: The UE can continue its communication session, and the network ensures that data and voice services are not interrupted.

The Handover Request Acknowledge procedure is crucial for facilitating smooth handovers within the mobile network, allowing UEs to move between cells without service interruption while maintaining efficient resource utilization.