Uplink Spatial Relation Switch for PUCCH and SRS
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR networks, there is a challenge in determining the uplink spatial relation for SRS and PUCCH transmissions when the network does not configure the necessary resources for beam training or when the beam information is outdated.
Innovation Solution
The proposed solution involves various alternative embodiments for the UE to derive the corresponding Tx beams for SRS and PUCCH transmissions. These include using the Rx beam for pathloss RS or CORESET reception, utilizing the Tx beam of a random access channel, or requesting the network to configure available resources for UL spatial relation switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the network configures resources for beam training, then the UE can determine accurate uplink spatial relations, but the network complexity and resource overhead increase
Solution Approach 1:
The UE autonomously determines uplink spatial relations by selecting from a codebook of beam pairs based on downlink measurements, without requiring explicit network configuration for each uplink transmission. The UE self-configures the spatial relation using pre-defined codebook indices selected based on measured downlink reference signals
Solution Approach 2:
The network pre-configures a codebook of downlink reference signals and uplink spatial relations before uplink transmission. The UE uses these pre-configured resources to autonomously determine spatial relations, eliminating the need for real-time network configuration and reducing signaling overhead
2Reliability
If the UE uses network-configured beam information, then the uplink transmission is reliable, but the system cannot adapt when beam information is outdated
Solution Approach 1:
The system transitions from static network-configured beam information to dynamic UE-autonomous beam selection. The UE continuously monitors downlink reference signals and adapts its uplink spatial relation selection based on current channel conditions, enabling real-time beam adaptation while maintaining transmission reliability through codebook-based spatial relation determination
Solution Approach 2:
The UE performs downlink measurements on reference signals and uses this feedback information to autonomously select appropriate uplink spatial relations from the codebook. This closed-loop approach ensures the UE adapts to changing channel conditions while maintaining reliable uplink transmissions
3Measurement precision
If the network provides detailed spatial relation configurations, then the UE can achieve precise beam alignment, but the signaling overhead and latency increase
Solution Approach 1:
The network provides a pre-defined codebook of spatial relation patterns that the UE can copy and apply directly to uplink transmissions. Instead of receiving detailed real-time configuration, the UE selects from pre-configured codebook entries, dramatically reducing signaling overhead and configuration time while maintaining precise beam alignment through codebook-based spatial relation determination
Data Source
AI summary
Methods and apparatus are provided for a UE to determine a UL spatial relation for an UL transmission in response to an unknown UL spatial relation switch. The UE may determine whether the UL spatial relation is based on an SRS transmission in UL, a CSI-RS in DL, or an SSB in the DL. If the UL spatial relation is based on the SRS transmission, the UE may select the UL spatial relation for the UL transmission corresponding to a Tx beam of the SRS transmission. If the UL spatial relation is based on the CSI-RS or the SSB, the UE may select the UL spatial relation for the UL transmission based on whether the unknown UL spatial relation switch is due to a corresponding resource for beam training not being configured by a communication network or a corresponding beam information being expired.