Joint SD Basis Selection for Low-Overhead Multi-TRP CSI
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Solution Overview
Problem
The overhead of channel state information (CSI) transmission in multiple transmission reception point (mTRP) configurations is significantly increased due to separate spatial domain (SD) basis selection per TRP or TRP group, which complicates coherent joint transmission (CJT) by requiring extensive reporting.
Innovation Solution
A UE groups SD bases associated with multiple TRPs into SD basis groups and transmits a joint SD basis selection indicator using a combination coefficients table, minimizing overhead by encoding and decoding this indicator to facilitate CJT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate SD basis selection per TRP or TRP group is used, then CJT can be enabled with detailed CSI, but CSI overhead is significantly increased
Solution Approach 1:
The patent combines separate SD basis selections from multiple TRPs into a joint SD basis selection. Instead of reporting separate basis selections for each TRP, the UE performs a unified joint selection across all TRPs and reports a single joint SD basis selection indicator. This merging reduces the quantity of CSI reports while maintaining the ability to support coherent joint transmission across multiple TRPs.
Solution Approach 2:
The joint SD basis selection indicator serves multiple TRPs simultaneously with a single report. This universal indicator can be used by multiple TRPs for coherent joint transmission, eliminating the need for separate indicators for each TRP and reducing overall CSI overhead while maintaining CJT functionality.
2Loss of information
If separate SD basis selection per TRP or TRP group is used, then detailed channel state information is available, but complexity of CSI reporting is increased
Solution Approach 1:
The patent merges multiple separate SD basis selection processes into a single joint selection process. The UE performs one unified joint SD basis selection across all TRPs instead of separate selections for each TRP, and reports a single joint indicator. This reduces the complexity of CSI reporting while maintaining detailed channel state information quality through the joint selection.
3Quantity of substance
If joint SD basis selection is implemented, then CSI overhead is reduced, but encoding and decoding complexity may increase
Solution Approach 1:
The patent segments the joint SD basis selection into manageable components using a codebook structure with combination coefficients. The joint selection is represented as a combination of basis vectors from individual TRP codebooks, allowing efficient encoding through index selection and decoding through linear combination operations. This segmentation prevents excessive complexity while achieving overhead reduction.
Solution Approach 2:
The patent changes the parameter representation from separate SD basis selections to a joint SD basis selection indicator that uses combination coefficients. This parameter transformation allows the system to represent the joint selection more compactly, reducing CSI overhead while maintaining manageable encoding and decoding complexity through the structured codebook approach.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may group a total quantity of spatial domain (SD) bases associated with multiple transmission reception points (TRPs) into one or more SD basis groups. The UE may select, for each respective SD basis group, one or more SD bases from the respective set of SD bases. The UE may identify, for each respective SD basis group, an index that represents the one or more SD bases selected for the respective SD basis group. The UE may transmit, to a network node, channel state information (CSI) that includes a joint SD basis selection indicator for the multiple TRPs, the joint SD basis selection indicator indicating, for each respective SD basis group, the respective index representing the one or more SD bases selected for the respective SD basis group. Numerous other aspects are provided.