Uplink Beam Control via Downlink TCI State Mapping
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Solution Overview
Problem
In future radio communication systems, the number of candidates for configuring uplink beam control is limited, leading to potential delays and resource consumption when reconfiguration is performed using higher layer signaling.
Innovation Solution
A user terminal assumes a spatial relation for uplink transmission to be the same as the transmission configuration indication state of a specific downlink channel or quasi-co-location assumption, allowing for efficient control of uplink beams without the need for RRC reconfiguration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reconfiguration using higher layer signaling is performed to use a large number of beam candidates, then the number of beam candidates increases, but delay occurs and resources are consumed
Solution Approach 1:
The patent pre-configures multiple beam candidates using higher layer signaling (RRC) before they are needed. The network can configure a set of TCI states or spatial relation information in advance, so when beam reconfiguration is needed, the UE can immediately select from the pre-configured candidates without waiting for additional RRC reconfiguration, thus reducing delay while maintaining adaptability
Solution Approach 2:
The patent divides beam configuration into two parts: (1) pre-configuration of multiple beam candidates using RRC signaling, and (2) dynamic selection among these candidates using MAC CE or DCI. This segmentation allows the system to maintain a large number of beam candidates while enabling fast switching through lower-layer signaling that does not cause RRC reconfiguration delay
2Adaptability or versatility
If reconfiguration using higher layer signaling is performed to use a large number of beam candidates, then the number of beam candidates increases, but resources are consumed
Solution Approach 1:
The patent segments the configuration process into RRC-level pre-configuration of beam candidates and MAC CE/DCI-level dynamic selection. This allows the system to configure multiple beam candidates efficiently at RRC level while using resource-light MAC CE or DCI for actual beam selection, reducing overall resource consumption compared to using RRC reconfiguration for each beam change
Solution Approach 2:
The patent uses TCI states from downlink channels as templates for uplink beam configuration. By copying the spatial relation information from DL TCI states to UL beam configurations, the system can support multiple beam candidates without proportionally increasing signaling overhead, as the same TCI state can serve both DL and UL configurations
3Manufacturing precision
If RRC reconfiguration is performed for beam control, then beam control accuracy is maintained, but communication overhead increases
Solution Approach 1:
The patent separates beam configuration into RRC-level candidate preparation and MAC CE/DCI-level active beam indication. This segmentation allows accurate beam control through proper configuration while reducing communication overhead by using compact MAC CE formats or DCI fields for beam selection instead of full RRC reconfiguration messages
Solution Approach 2:
The patent makes TCI states multi-functional by using them for both downlink reception configuration and uplink transmission beam control. This universality reduces communication overhead because the same TCI state configuration serves dual purposes, eliminating the need for separate beam configuration signaling for UL and DL
Data Source
AI summary
A user terminal according to one aspect of the present disclosure includes a control section that assumes that spatial relation of specific uplink transmission is same as a transmission configuration indication (TCI) state of a specific downlink channel or quasi-co-location (QCL) assumption, and a transmitting section that performs the specific uplink transmission by using the spatial relation. According to one aspect of the present disclosure, control of a UL beam can be appropriately performed.