SCell Management During Conditional PCell Handover
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Solution Overview
Problem
In conditional handover scenarios in wireless communication systems, the secondary cell (SCell) configuration provided to wireless devices may be outdated by the time the handover occurs, leading to delayed carrier aggregation (CA) and dual connectivity (DC) setups, as the device executes the handover only when specific conditions are met, causing inefficiencies in resource management.
Innovation Solution
A method where a wireless device evaluates the SCell conditions upon determining that the Primary Cell (PCell) condition is met and transmits a handover complete message to the target PCell, allowing for immediate CA and/or DC operations with reported SCells, enabling the device to start SCell addition without additional configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wireless device executes handover only when the PCell condition is met (conditional handover), then the handover robustness is improved, but the SCell configuration becomes outdated and CA/DC setup is delayed
Solution Approach 1:
The network pre-configures SCell conditions and candidate SCells before the handover is executed. When the PCell condition is met, the device already has valid SCell configurations ready to apply immediately, eliminating the delay between handover execution and SCell addition. This preliminary preparation of SCell configurations resolves the contradiction by ensuring both handover robustness (through conditional execution) and timely SCell addition (through pre-prepared configurations).
Solution Approach 2:
The patent implements dynamic evaluation of SCell conditions at the moment of handover execution. The device evaluates whether SCell conditions are satisfied based on current channel measurements and network state, rather than using static pre-configured SCell lists. This dynamic approach ensures that SCell configurations remain valid and up-to-date even when handover is delayed, resolving the outdated configuration problem while maintaining handover robustness.
2Loss of information
If the target BS waits for measurement results from the wireless device before configuring SCells, then the SCell configuration is up-to-date, but the CA and DC setup is significantly delayed
Solution Approach 1:
The network performs preliminary configuration of candidate SCells and their associated conditions before handover execution. The target BS prepares a list of potential SCells with their configuration parameters and evaluation criteria in advance. When handover is triggered, the device can immediately evaluate these pre-prepared configurations against current measurements and activate suitable SCells without waiting for new measurement reports, thus maintaining configuration accuracy while accelerating CA/DC setup.
Solution Approach 2:
The patent configures multiple candidate SCells with different conditions and parameters in advance, more than what would traditionally be configured. The device evaluates these pre-configured candidates and selects the most appropriate ones based on current channel conditions. This approach provides up-to-date SCell configurations without requiring waiting for measurement results, as the pre-configured candidates already cover various possible channel states.
3Productivity
If the source BS provides measurement results to the target BS in advance, then the target BS can setup CA and DC immediately, but the SCell configuration may be outdated when handover is actually executed
Solution Approach 1:
The patent implements dynamic condition evaluation for SCells at handover execution time. Instead of relying solely on static measurement results provided in advance, the device evaluates SCell conditions based on current channel measurements and network state when the handover is actually executed. This dynamic evaluation ensures that SCell configurations remain valid and appropriate even though measurement results were provided earlier, resolving the contradiction between early setup speed and configuration validity.
Solution Approach 2:
The system incorporates feedback mechanisms where the device continuously monitors channel conditions and SCell performance metrics. When handover is executed, the device provides updated feedback information about current channel state and SCell evaluation results to the network. This feedback loop allows the network to adjust and optimize SCell configurations in real-time, ensuring their validity despite being prepared in advance, while maintaining fast CA/DC setup.
Data Source
AI summary
A method and apparatus for managing SCells during a conditional PCell handover in a wireless communication system is provided. A wireless device receives, from the source PCell, a handover command including a PCell condition for a target PCell. The handover command includes at least one of Secondary Cell (SCell) conditions for target SCells. A wireless device evaluates the SCell conditions for the target SCells upon determining that the PCell condition for the target PCell is met. A wireless device transmits, to the target PCell, a handover complete message including result of the evaluation of the SCell conditions for the target SCells.