Default QCL Assumptions for Single-DCI Multi-TRP Beam Failure Recovery
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR, there is a need to improve the default quasi co-location (QCL) assumptions for user equipment (UE) and base stations after beam failure detection, as existing methods are inconsistent and confusing, especially in single-DCI based multiple-TRP communication scenarios.
Innovation Solution
The proposed solution involves providing default QCL assumptions for UEs and base stations to apply after identifying a new beam in response to beam failure detection, by continuing to use the default QCL assumptions based on the lowest codepoint among TCI codepoints containing two different states, or resetting them to the lowest CORESET-ID, selected RS index, CORESET-0, or the first TCI state, ensuring consistent QCL assumptions before and after beam failure recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing default QCL assumption methods are used after beam failure detection, then beam failure recovery can be performed, but the QCL assumptions become inconsistent and confusing
Solution Approach 1:
The patent changes the parameter used for default QCL assumptions from CORESET-based to TCI codepoint-based. Specifically, it uses the lowest TCI codepoint among TCI codepoints containing two different states to determine the default QCL assumption, thereby changing the underlying parameter structure to achieve both reliability and consistency
Solution Approach 2:
The patent establishes predetermined rules for selecting default QCL assumptions before beam failure occurs. By pre-defining that the lowest TCI codepoint with two different states shall be used, the system avoids confusion during recovery since the selection criterion is already established in advance
2Ease of operation
If default QCL assumptions are reset to lowest CORESET-ID after beam failure, then communication can resume, but confusion arises in single-DCI based multiple-TRP communication
Solution Approach 1:
The patent introduces TCI codepoints as an intermediary layer between the beam failure detection and the QCL assumption selection. Instead of directly resetting to CORESET-ID, the system uses TCI codepoints (which contain information about multiple TRPs) as the mediator to determine the new default QCL assumption, thereby preserving information about the multiple-TRP structure
Solution Approach 2:
The patent segments the QCL assumption selection process into distinct steps: first identifying TCI codepoints containing two different states, then selecting the lowest such codepoint, and finally using it to determine the default QCL assumption. This segmentation makes the process more manageable and less confusing than a direct reset
Data Source
AI summary
Default QCL assumptions for UEs and base stations to apply after identifying a new beam in response to beam failure detection are provided for single-DCI multi-TRP communication. In one aspect, a default QCL assumption for PDSCH after beam failure detection may be applied based on TCI states corresponding to a lowest codepoint among the TCI codepoints containing two different states. In another aspect, a default QCL assumption for PDSCH after beam failure detection may be applied based on at least one of: a lowest CORESET-ID in a latest monitored slot, a selected RS index during beam failure recovery, CORESET-0, or a first TCI state corresponding to the lowest TCI codepoint indicating two TCI states. Additionally, default QCL assumptions for UEs and base stations to apply during beam failure recovery are provided for single-DCI multi-TRP communication when the UE is not configured with a set of beam failure detection resources.