Conditional Handover Candidate Cell Selection
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Solution Overview
Problem
In LTE systems, UE handover from a source cell to a target cell often fails due to handover occurring too late, too early, or to a wrong cell, leading to radio link failures, and existing methods do not allow the UE to independently select a suitable target cell, resulting in inefficient power consumption and processing resource usage for eNBs.
Innovation Solution
The UE is empowered to select a target cell based on handover conditions and candidate cells indicated in the RRCConnectionReconfiguration message, with the option to release the handover configuration if none meet the conditions within a configured timer or upon specific events, allowing for timely and resource-efficient handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source eNB selects the target cell based on measurement report, then the handover decision can be made centrally, but the UE may move back from the edge of the source cell to the center after transmitting the measurement report, making the selected target cell unsuitable
Solution Approach 1:
The patent applies preliminary action by having the UE evaluate multiple candidate cells and pre-determine a target cell before actually executing the handover. The UE continuously monitors candidate cells and selects a target cell in advance, so when handover is triggered, the UE can immediately switch to the pre-selected target cell, avoiding the delay and inaccuracy of real-time selection after movement.
Solution Approach 2:
The patent implements self-service by empowering the UE to autonomously select the target cell based on its own movement status and signal quality measurements, rather than relying solely on the source eNB's selection. The UE independently evaluates candidate cells, determines handover necessity, and selects the most suitable target cell, making the handover process adaptive to the UE's actual position and conditions.
2Reliability
If conditional handover configuration is provided with multiple candidate cells, then handover options are increased, but power consumption and processing time increase for the UE to continuously evaluate all candidate cells
Solution Approach 1:
The patent applies partial action by having the UE evaluate only the necessary subset of candidate cells rather than continuously monitoring all configured candidates. The UE selectively evaluates candidate cells based on current signal conditions and movement status, performing measurements only when needed and releasing the handover configuration when no suitable target is found, thereby reducing unnecessary power consumption while maintaining handover reliability.
3Reliability
If the UE continuously evaluates all candidate cells in conditional handover configuration, then the most suitable target cell can be selected, but processing resources of the eNB are consumed and handover configuration must be maintained for extended periods
Solution Approach 1:
The patent applies preliminary action by having the UE pre-select a target cell from candidate cells before actual handover execution. The UE continuously evaluates candidate cells in the background and determines a target cell in advance, so when handover conditions are met, the UE can immediately execute the handover to the pre-determined target cell, reducing the complexity of real-time configuration management and eNB processing resources.
Data Source
AI summary
Methods and apparatus for UE handover are disclosed. One method of a UE comprising receiving a handover configuration related to a conditional handover command including at least one handover condition and a plurality of candidate cells, wherein the handover condition is configured per candidate cell; and selecting a target cell from the plurality of candidate cells in response to the target cell meeting the corresponding handover condition. The methods and apparatus herein not only increase the likelihood of a successful handover while the power consumption and/or processing time for the UE are acceptable, the processing resource is also saved for eNB.