Target Cell BWP Selection in L1-L2 Inter-Cell Mobility
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Solution Overview
Problem
Current 5G NR wireless networks face challenges in determining the active bandwidth parts (BWPs) for uplink and downlink in target cells during L1/L2 inter-cell mobility, leading to increased latency and interruption times due to the need for complete L2 resets and RRC signaling.
Innovation Solution
The UE determines the active BWPs in the target cell based on indications received in the L1/L2 inter-cell mobility configuration, selecting appropriate channel and beam configurations to access the target cell, resolving ambiguity through pre-defined or indicated BWP configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 handovers with complete L2 resets and RRC signaling are used for inter-cell mobility, then reliability of cell switching is improved, but latency and interruption time increase
Solution Approach 1:
The patent segments the mobility procedure into L1/L2 rapid switching for normal operations and retains L3 handovers as a fallback for exceptional cases. This segmentation allows the system to achieve low-latency mobility through MAC CE-based BWP switching and TCI state updates without requiring complete L2 resets, while maintaining reliability through the availability of traditional RRC signaling when needed.
Solution Approach 2:
The patent applies preliminary action by pre-configuring multiple BWPs and TCI states in advance through RRC signaling before mobility is needed. During actual inter-cell mobility, the UE can rapidly switch between pre-configured BWPs and activate pre-defined TCI states using MAC CE commands, eliminating the need for real-time RRC reconfiguration and reducing interruption time while maintaining reliability.
2Adaptability or versatility
If multiple BWPs are configured for target candidate cell, then adaptability of channel configurations is improved, but ambiguity in determining active BWP increases
Solution Approach 1:
The patent introduces TCI states as an intermediary mechanism that resolves the ambiguity of determining active BWP during L1/L2 inter-cell mobility. The TCI state explicitly indicates which BWP should be activated in the target cell, serving as a mediator between the gNB's mobility decision and the UE's BWP configuration. This intermediary eliminates uncertainty while preserving the adaptability benefits of multiple BWP configurations.
Solution Approach 2:
The patent uses parameter changes by dynamically updating the active BWP identification through TCI state updates via MAC CE signaling. Instead of requiring complex UE interpretation of multiple BWP configurations, the system changes the active BWP parameter directly through TCI state indication, simplifying the UE's decision-making process while maintaining the flexibility of having multiple pre-configured BWPs available for different scenarios.
3Loss of time
If L1/L2 mobility signaling is used instead of RRC signaling, then processing time is reduced, but clarity in BWP activation indication may be insufficient
Solution Approach 1:
The patent applies preliminary action by pre-configuring all necessary BWP parameters, TCI states, and channel configurations through RRC signaling before L1/L2 mobility execution. This preliminary configuration ensures that when MAC CE commands are received for rapid switching, the UE already has complete and unambiguous information about which BWPs to activate and how to configure channels, eliminating information loss while maintaining fast processing.
Solution Approach 2:
The patent uses TCI states as an intermediary that bridges the gap between compact L1/L2 MAC CE signaling and the detailed BWP configuration requirements. The TCI state carries explicit BWP activation indications without requiring lengthy RRC messages, thus maintaining processing speed while ensuring clarity in BWP activation indication through the standardized TCI state parameter structure.
Data Source
AI summary
According to some embodiments, a method is performed by a wireless device capable of layer one (L1)/layer two (L2) inter-cell mobility. The method comprises receiving a L1/L2 inter-cell mobility configuration comprising at least one target candidate cell configuration. The at least one target candidate cell configuration comprises one or more bandwidth part (BWP) configurations. The method further comprises obtaining at least one indication of at least one of the BWP configurations of a target candidate cell to be activated; receiving a L1/L2 inter-cell mobility execution command including an indication of one target candidate cell configuration for a target cell; and determining at least one active BWP of the target cell in which the wireless device is to operate in the target cell based on the indicated target candidate cell configuration.