Conditional Handover Occupied Channel Notification
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Solution Overview
Problem
In NR-U SA systems, the lack of a reliable channel for control signaling due to unlicensed band occupancy leads to challenges in handover operations, as existing mobility procedures are not equipped to handle temporary channel occupancy issues.
Innovation Solution
The UE device receives a conditional handover command and determines if the target frequency is available. If occupied, it notifies the serving base station with an indication, which may include a measurement report, allowing the network to manage handovers more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control signaling is performed over unlicensed bands in NR-U SA systems, then the system can operate standalone without licensed anchor cells, but the reliability of control signaling deteriorates due to channel occupancy by other systems
Solution Approach 1:
The patent applies preliminary action by performing Listen-Before-Talk (LBT) procedures and Clear Channel Assessment (CCA) checks before transmitting control signaling on unlicensed bands. This advance detection of channel occupancy prevents transmission conflicts and improves the reliability of handover commands and other control signaling in NR-U SA systems.
2Ease of operation
If handover procedures use traditional mobility management, then the system follows existing protocols, but handover failures increase when target channels are occupied by other systems
Solution Approach 1:
The patent implements feedback mechanisms where the receiving end reports channel occupancy status back to the transmitting end. This feedback loop allows the system to adapt handover procedures dynamically - when target channels are found occupied during handover execution, the system can trigger alternative actions such as selecting different target cells or adjusting handover parameters, thereby improving handover success rate while maintaining procedural simplicity.
3Object-affected harmful factors
If the system performs clear channel assessment before transmission, then coexistence with other systems is improved, but the time required for handover operations increases
Solution Approach 1:
The patent applies partial action by performing LBT/CCA procedures selectively - primarily on uplink control signaling transmissions rather than all signals. This approach provides sufficient channel access control to ensure fair coexistence with other systems while minimizing the time overhead added to handover operations. The system performs assessments only where necessary to prevent harmful interference, rather than continuously monitoring all channels.
Data Source
AI summary
A user equipment (UE) device receives, from base station providing a source cell, a conditional handover command identifying a target frequency on a target cell for conditional handover. After determining that conditions have been met for the conditional handover, the UE device observes the target frequency. If the target frequency is occupied, the UE device transmits, to the serving base station, an indication that the target frequency is unavailable for the conditional handover. The indication may include, or be transmitted with, a measurement report.