Reference Signal QCL Mapping for Low-Latency Beam Switching
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently updating the quasi co-location (QCL) of periodic-tracking reference signals (P-TRS) due to increased latency in radio resource control (RRC) reconfiguration processes when switching beams, and there is a need for reduced latency in configuring aperiodic-tracking reference signals (A-TRS) and selecting periodic reference signals for radio link failure or beam failure detection.
Innovation Solution
The method involves determining the QCL for P-TRS based on the QCL of an associated A-TRS, implicitly updating the P-TRS QCL to reduce latency, and selecting a P-TRS as the radio link failure or beam failure detection reference signal to avoid explicit RRC reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If explicit RRC reconfiguration is used to update QCL for P-TRS during beam switching, then configuration accuracy is ensured, but latency increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple TCI states including both A-TRS and P-TRS configurations in advance. When beam switching is needed, the UE can immediately activate a pre-configured TCI state without waiting for RRC reconfiguration, thus reducing latency while maintaining configuration accuracy through pre-validation of QCL parameters.
Solution Approach 2:
The patent introduces MAC-CE as an intermediary mechanism between the RRC layer and physical layer for QCL updates. MAC-CE provides a faster signaling path than RRC reconfiguration alone, allowing QCL parameter updates for P-TRS to be transmitted and activated with lower latency while still ensuring configuration accuracy through structured parameter validation.
2Adaptability or versatility
If A-TRS is configured independently without association with P-TRS, then configuration flexibility increases, but system complexity increases
Solution Approach 1:
The patent merges A-TRS and P-TRS configurations by associating them through a common TCI state. This allows the UE to determine QCL for P-TRS based on the QCL of associated A-TRS, reducing the number of independent configuration parameters needed while maintaining configuration flexibility through the unified TCI state structure that can accommodate both signal types.
3Speed
If P-TRS is selected for beam failure detection without explicit RRC reconfiguration, then response speed increases, but selection accuracy may decrease
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple candidate TCI states with their associated P-TRS and A-TRS parameters before beam failure detection is needed. When beam failure is detected, the UE can immediately select from pre-evaluated candidates based on stored quality metrics, achieving fast response while maintaining selection accuracy through prior systematic evaluation of reference signals.
Solution Approach 2:
The patent implements feedback mechanisms where the UE continuously monitors reference signal quality and provides feedback to the network about beam conditions. This feedback loop enables the UE to identify suitable P-TRS for beam failure detection based on actual measured quality, ensuring accurate selection while maintaining fast response through ongoing monitoring rather than waiting for network directives.
Data Source
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AI summary
Certain aspects of the present disclosure provide techniques for configuring reference signals. A method that may be performed by a user equipment (UE) includes receiving a control message indicating a first quasi co-location (QCL) for an aperiodic- tracking reference signal (A-TRS), the A-TRS being associated with a periodic-tracking reference signal (P-TRS), determining a second QCL for the P-TRS based on the first QCL for the A-TRS, setting a receive beam for reception of the P-TRS based on the second QCL of the P-TRS, and decoding one or more frames based on channel statistics estimated via the P-TRS received via the receive beam.