Default CSI-RS QCL Assumption for Minimum Capability UEs
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Solution Overview
Problem
User equipment with minimum capability on active transmission configuration indicator (TCI) states face challenges in determining the quasi-colocation (QCL) assumption for channel state information reference signals (CSI-RS) due to limitations in dynamic switching across slots, especially when the scheduling delay is less than the beam switching latency threshold.
Innovation Solution
A method where user equipment (UE) with minimum capability on active TCI states determines that a physical downlink shared channel (PDSCH) is not scheduled on the same symbol as CSI-RS and derives a QCL assumption based on a default CSI-RS QCL assumption, following a default PDSCH QCL assumption or a control resource set (CORESET) with a lowest identifier, allowing dynamic switching for CSI-RS reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE dynamically switches TCI states for CSI-RS reception across slots, then the beam switching capability is improved, but the scheduling delay must be sufficient to exceed the beam switching latency threshold
Solution Approach 1:
The patent applies preliminary action by pre-configuring default QCL assumptions and TCI states before they are needed. The UE is provided with default QCL assumptions for aperiodic CSI-RS through RRC configuration, and default TCI states are established in advance for PDSCH reception. This allows the UE to have ready-to-use beam configurations without requiring dynamic switching when scheduling delay is insufficient, thus resolving the contradiction between beam switching capability and scheduling delay requirements.
2Device complexity
If the UE uses minimum capability on active TCI states, then the device complexity is reduced, but the ability to determine QCL assumption for CSI-RS is limited
Solution Approach 1:
The patent applies self-service by enabling the UE to autonomously determine QCL assumptions for aperiodic CSI-RS based on pre-configured default assumptions and the association between CSI-RS resources and TCI states. When dynamic TCI state switching is not feasible, the UE self-determines the appropriate QCL assumption using the default configuration and the relationship between CSI-RS resource indicators and TCI states, eliminating the need for complex real-time network control while maintaining accurate QCL determination.
3Adaptability or versatility
If the scheduling delay is less than the beam switching latency threshold, then the scheduling flexibility is improved, but the UE cannot reliably switch beams for CSI-RS reception
Solution Approach 1:
The patent resolves this contradiction by establishing default QCL assumptions and default TCI states in advance through RRC configuration. When scheduling delay is insufficient for dynamic beam switching, the UE falls back to these pre-configured defaults, ensuring reliable CSI-RS reception without requiring adequate scheduling delay. This preliminary configuration approach allows flexible scheduling while maintaining beam switching reliability.
Solution Approach 2:
The patent introduces an intermediary mechanism where the association between CSI-RS resource indicators and TCI states serves as a mediator. When dynamic beam switching cannot be performed due to insufficient scheduling delay, the UE uses the CSI-RS resource indicator to identify the associated default TCI state, which then provides the appropriate QCL assumption. This intermediary relationship enables reliable beam selection without requiring direct dynamic switching.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment may determine that a physical downlink shared channel (PDSCH) is not scheduled on a same symbol as a channel state information reference signal (CSI-RS), wherein the UE has a minimum capability on active transmission configuration indicator (TCI) states. The user equipment may derive a quasi-colocation (QCL) assumption of the CSI-RS based at least in part on a default CSI-RS QCL assumption for UEs with the minimum capability on active TCI states. Numerous other aspects are provided.