Handover Validity Check for Signaling Delay in NTN
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Solution Overview
Problem
Signaling delay during handover in Non-Terrestrial Networks (NTN) leads to invalid mobility commands due to propagation delays, causing handover failures and service delays in satellite-based communication systems.
Innovation Solution
A wireless device method that includes transmitting measurement reports based on events for both the current and target cells, with a validity check for handover commands to prevent improper mobility due to propagation delays, using a new validity timer to assess the validity of handover configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If handover command is transmitted in NTN environment, then mobility control is achieved, but propagation delay causes invalid mobility commands and handover failures
Solution Approach 1:
The network pre-configures the wireless device with multiple validity timers (first validity timer for target cell, second validity timer for source cell) before handover execution. These timers are set in advance to cover the propagation delay period, allowing the device to validate the handover command against future cell states and prevent execution of invalid mobility commands.
Solution Approach 2:
The wireless device continuously monitors cell events (entry and leave events) and provides feedback to validate whether the handover command remains valid. The device checks if the target cell still satisfies entry conditions and if the source cell still satisfies leave conditions, using the pre-configured validity timers to determine whether to execute or cancel the handover based on current cell states.
2Productivity
If wireless device performs mobility to target cell based on measurement report, then handover is executed, but propagation delay causes target cell to no longer satisfy entry conditions
Solution Approach 1:
The network pre-configures the wireless device with validity timers and cell event conditions before handover execution. The device uses these pre-configured parameters to validate the handover command against future cell states, ensuring that the target cell still satisfies entry conditions before executing the handover, thus preventing invalid mobility executions.
Solution Approach 2:
The wireless device continuously monitors whether the target cell satisfies the entry conditions and provides feedback validation. Before executing handover, the device checks if the target cell still meets the configured entry conditions (e.g., signal quality thresholds), and only executes handover if validation succeeds, otherwise it cancels the handover to avoid invalid mobility.
3Reliability
If wireless device checks validity of handover command, then improper mobility is prevented, but additional validation complexity is introduced
Solution Approach 1:
The wireless device autonomously performs validity checks using pre-configured parameters (validity timers and cell event conditions) provided by the network. The device independently monitors cell states, validates handover commands against current conditions, and decides whether to execute or cancel handover without requiring additional network intervention, thus reducing signaling overhead while maintaining high reliability.
Solution Approach 2:
The network dynamically configures validity timer durations and cell event conditions based on NTN propagation delay characteristics. By adjusting these parameters (timer values, threshold levels) to match the specific delay environment, the validation mechanism becomes adaptive and efficient, reducing unnecessary complexity while ensuring accurate validity assessment for handover execution.
Data Source
AI summary
A method and apparatus for handling signaling delay for handover is provided. A wireless device transmits a measurement report based on a first event for a first cell, receives a handover command which commands a handover to the first cell, and checks validity of the handover command based on the first event for the first cell and/or a second event for a second cell other than the first cell.