NR-U User Terminal SSB Indexing for QCL Under LBT Failure
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Solution Overview
Problem
In the context of next-generation mobile communication systems using unlicensed bands, the proper consideration of Quasi-Co-Location (QCL) assumptions between Synchronization Signal Blocks (SSBs) is not adequately addressed, particularly in the presence of Listen Before Talk (LBT) failures, leading to potential decreases in communication throughput.
Innovation Solution
A user terminal equipped with a receiving section to acquire effective SSB indexes based on Demodulation Reference Signals (DMRS) of PBCH within SSBs, determining the number of effective SSB indexes and the start location of an SSB burst within a Discovery Reference Signal (DRS) transmission window, enabling proper QCL assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Listen Before Talk (LBT) is performed in unlicensed bands, then channel access is improved, but communication throughput deteriorates due to LBT failures
Solution Approach 1:
The system performs preliminary actions by pre-configuring multiple SSB indexes and their corresponding QCL assumptions before LBT execution. When LBT succeeds, the appropriate SSB index is selected based on the actual transmission outcome. This preliminary configuration enables the system to adapt to LBT results without causing throughput degradation.
Solution Approach 2:
The invention changes the parameter of SSB index configuration dynamically based on LBT outcomes. Multiple SSB indexes are configured with different QCL assumptions, and the system selects the appropriate index according to whether LBT succeeds or fails. This parameter adaptation resolves the contradiction by maintaining reliable channel access while preserving communication throughput through flexible SSB index selection.
2Ease of operation
If SSB is semi-statically transmitted using ssb-PositionsInBurst, then transmission simplicity is improved, but QCL assumption judgment deteriorates in consideration of LBT failure
Solution Approach 1:
The invention segments the SSB transmission configuration by associating multiple SSB indexes with different QCL assumptions. Instead of using a single semi-static configuration, the system divides the SSB resources into multiple indexed configurations, each suitable for different LBT outcomes. This segmentation enables precise QCL assumption judgment while maintaining the simplicity of semi-static transmission through structured configuration.
Solution Approach 2:
The invention introduces dynamics into the semi-static SSB configuration by enabling the system to select among multiple pre-configured SSB indexes based on LBT results. The ssb-PositionsInBurst parameter becomes dynamic in its selection rather than fixed in its application, allowing the system to adapt QCL assumptions to actual transmission conditions while retaining the efficiency of semi-static configuration management.
3Adaptability or versatility
If multiple SSB indexes are configured, then QCL assumption flexibility is improved, but device complexity increases
Solution Approach 1:
The invention applies universality by designing a unified SSB index management mechanism that handles multiple SSB indexes through a single configuration framework. The same ssb-PositionsInBurst parameter structure is used regardless of the number of SSB indexes, and the selection process follows a universal rule based on LBT outcomes. This multi-functional approach provides QCL assumption flexibility without proportionally increasing device complexity.
Data Source
AI summary
To properly consider the QCL assumption about SSBs in an NR-U carrier, a user terminal according to one aspect of the present disclosure is characterized by having a receiving section that receives a Synchronization Signal Block (SSB), and a control section which acquires an effective SSB index based on a demodulation reference signal (DeModulation Reference Signal (DMRS)) of a broadcast channel (Physical Broadcast Channel (PBCH)) included in the SSB, and from a payload of the PBCH, acquires at least one of information on the number of effective SSB indexes to be transmitted and a start location index of an SSB burst including the SSB within a Discovery Reference Signal (DRS) transmission window.