Radio Link Monitoring Across 5G Bandwidth Part Switching
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Solution Overview
Problem
The issue in existing 5G systems is the uncertainty regarding which reference signal the UE should monitor for Radio Link Monitoring (RLM) after switching downlink bandwidth parts (BWPs) without changing the cell-defining synchronization signal block (SSB).
Innovation Solution
The UE continues to use the first SSB associated with the original BWP for RLM measurements after switching to a new BWP, even if the reference signal type is set to SSB, ensuring consistent RLM monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE switches downlink bandwidth parts (BWPs) without changing the cell-defining SSB, then the adaptability of the system is improved, but the uncertainty of RLM reference signal monitoring increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple SSBs with different SSB indexes before BWP switching occurs. The network pre-associates each BWP with specific SSB indexes, so when BWP switching happens, the UE already has the necessary reference signal information ready to continue RLM measurements without interruption or uncertainty.
Solution Approach 2:
The patent uses SSB indexes as an intermediary to bridge the relationship between BWPs and reference signals. Instead of directly linking BWPs to physical SSB resources, the SSB indexes serve as a stable reference layer that mediates the connection, allowing BWP switching while maintaining consistent RLM monitoring through the intermediary index references.
2Reliability
If the UE continues to use the first SSB for RLM measurements after BWP switching, then the reliability of RLM monitoring is maintained, but the complexity of reference signal management increases
Solution Approach 1:
The patent applies universality by making the cell-defining SSB serve multiple functions simultaneously. The same SSB (identified by a specific SSB index) is used both for initial cell access and for continuous RLM measurements after BWP switching. This multi-functionality reduces complexity because the UE doesn't need to manage separate reference signals for different purposes - the same SSB index reference works universally across BWP configurations.
3Adaptability or versatility
If the network configures multiple SSBs with different SSB indexes for different BWPs, then the adaptability to different BWP configurations is improved, but the loss of information about which SSB to monitor increases
Solution Approach 1:
The patent applies feedback by having the network explicitly indicate the appropriate SSB index to the UE through downlink control information (DCI) or higher-layer signaling when configuring BWPs. This feedback mechanism ensures the UE receives clear guidance on which SSB index to monitor for RLM, preventing information loss despite the presence of multiple configured SSBs for different BWPs.
Data Source
AI summary
When a downlink bandwidth part (BWP) is switched from a first BWP to a second BWP without a change of a cell defining synchronization signal block (SSB), if a reference signal type for Radio Link Monitoring (RLM) is set to an SSB type, a radio terminal (12) continues to use for RLM measurements a first SSB associated with the first BWP after switching of the downlink BWP to the second BWP. This for example enables the radio terminal to monitor a suitable Reference Signal (RS) for RLM measurements after switching of the DL active BWP.