Reference Signal QCL Switching for Low-Latency Beam Updates
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Solution Overview
Problem
Existing wireless communication technologies, such as NR and LTE, face challenges in efficiently updating the quasi co-location (QCL) of periodic-tracking reference signals (P-TRS) due to high 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) to enhance beam management.
Innovation Solution
The method involves determining the QCL for P-TRS based on the QCL of an associated A-TRS, allowing implicit updates without additional RRC reconfiguration latency, and selecting a P-TRS as a radio link failure (RLF) or beam failure detection (BFD) reference signal to monitor control resource set (CORSET) quality, thereby reducing latency in beam switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RRC reconfiguration process is used to update QCL for P-TRS when switching beams, then beam switching can be performed, but high latency is introduced
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple QCL assumptions for P-TRS (first QCL assumption and second QCL assumption) before beam switching is needed. When beam switching occurs, the UE can immediately activate the appropriate pre-configured QCL assumption without waiting for RRC reconfiguration, thereby reducing latency while maintaining beam switching capability
Solution Approach 2:
The patent implements dynamics by enabling the UE to dynamically switch between different QCL assumptions (first and second) based on beam switching events. The network can trigger the UE to switch QCL assumptions through MAC CE or DCI signaling, allowing adaptive response to changing beam conditions without the rigidity of static RRC reconfiguration
2Reliability
If explicit RRC reconfiguration is used to configure A-TRS and BFD signals, then accurate configuration is achieved, but latency increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the UE with multiple QCL assumptions for P-TRS and A-TRS through RRC signaling before they are needed. This preliminary configuration maintains accuracy while enabling faster activation through subsequent MAC CE or DCI triggers, reducing configuration latency for A-TRS and BFD signals
Solution Approach 2:
The patent introduces MAC CE and DCI signaling as intermediaries between the network and UE for QCL assumption activation. These intermediary signaling mechanisms enable fast, accurate configuration updates without requiring full RRC reconfiguration, thereby reducing latency while maintaining configuration reliability for A-TRS and BFD signals
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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.