Default Spatial Relation for SRS and Uplink Control Beams
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Solution Overview
Problem
In wireless communication systems, user equipment (UE) may face challenges in determining a spatial relation for uplink channels or signals when not configured with control resource sets (CORESETs) or activated physical downlink shared channel transmission configuration indication (TCI) states, leading to mismatches between UE and base station assumptions, which can result in poor channel estimation and reduced spectral efficiency.
Innovation Solution
The UE determines a default spatial relation for uplink channels or signals based on predefined rules when no CORESETs or activated TCI states are available, using the lowest identifier of configured uplink resources or default TCI states to resolve ambiguities and ensure consistent beam alignment with the base station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE determines spatial relation based on CORESET or activated PDSCH TCI state, then the spatial relation accuracy is improved, but the device complexity increases due to additional configuration and state management requirements
Solution Approach 1:
The base station pre-configures multiple PDSCH TCI states and activates appropriate states before uplink transmission is needed. This preliminary configuration ensures that when the UE needs to determine spatial relation, the necessary TCI states are already available, improving accuracy while managing complexity through advance preparation rather than real-time computation
Solution Approach 2:
The patent uses activated PDSCH TCI states as temporary, context-specific references for spatial relation determination. These activated states serve as lightweight, disposable references that are activated only when needed for specific uplink channels or signals, avoiding the need for permanent complex configuration structures
2Reliability
If the UE uses default spatial relation determination when no CORESET or activated TCI states are available, then the system reliability is improved by avoiding complete failure, but the measurement precision deteriorates due to lack of optimal beam information
Solution Approach 1:
The base station ensures that at least one PDSCH TCI state is activated and configured before the UE needs to determine spatial relation for uplink transmission. This cushioning configuration prevents the UE from being in a state where no spatial relation can be determined, ensuring fallback reliability while maintaining the ability to use precise beam information when available
Solution Approach 2:
The UE autonomously determines spatial relation using the activated PDSCH TCI state with the lowest identifier when no CORESET is configured. This self-service mechanism allows the UE to independently resolve spatial relation without requiring additional base station intervention or complex signaling, improving reliability while keeping the mechanism simple
Data Source
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AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine that a control resource set (CORESET) is not configured for an active downlink bandwidth part of a component carrier (CC) of the UE. The UE may determine that a transmission configuration indication (TCI) state is not activated for a physical downlink shared channel (PDSCH) of the active downlink bandwidth part of the CC. The UE may determine a default spatial relation for an uplink control channel or uplink signal for the CC based at least in part on determining that the CORESET is not configured for the active downlink bandwidth part of the CC and that the TCI state is not activated for the PDSCH of the active downlink bandwidth part of the CC. Numerous other aspects are provided.