CSI Non-Zero Coefficient Bitmaps for Lower 3D Feedback Overhead
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Solution Overview
Problem
Existing wireless communication systems, particularly 5G NR, face challenges in reducing the reporting overhead of channel state information (CSI) due to the increased bitmap size for non-zero coefficients (NZCs) in three-dimensional domains, which is exacerbated by high or medium UE velocities.
Innovation Solution
A two-stage indication method is introduced for CSI reporting, where a first coefficient selection bitmap indicates NZC locations in a first domain and a second bitmap provides corresponding NZC locations in the time domain, exploiting channel sparsity to reduce overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a three-dimensional bitmap is used to indicate non-zero coefficient locations in spatial, frequency, and time domains, then CSI reporting accuracy is improved, but reporting overhead increases significantly
Solution Approach 1:
The patent segments the three-dimensional bitmap indication into two stages: first indicating non-zero coefficient locations in spatial and frequency domains, then indicating corresponding time domain locations separately. This segmentation reduces the immediate overhead while maintaining complete three-dimensional channel state information reporting capability.
Solution Approach 2:
The patent transforms the three-dimensional bitmap representation by separating spatial-frequency domain indications from time domain indications, effectively changing how the dimensional information is structured and transmitted to reduce overhead while preserving accuracy.
2Reliability
If comprehensive channel state information is reported for all domains, then downlink precoding performance is improved, but signaling complexity increases
Solution Approach 1:
The patent divides comprehensive channel state information reporting into segmented stages, where spatial-frequency domain information is reported first and time domain information is reported subsequently, reducing signaling complexity while maintaining complete information for downlink precoding.
Solution Approach 2:
The patent performs preliminary indication of spatial and frequency domain non-zero coefficient locations before indicating time domain locations, allowing the receiver to prepare appropriate data structures and reduce processing complexity when receiving the complete three-dimensional information.
Data Source
AI summary
A UE measures multiple occasions of CSI-RS. The UE also transmits, at a first stage, a first coefficient selection bitmap for CSI based on measurement of the CSI-RS and associated with a first domain and a second domain, first the coefficient selection bitmap indicating locations of NZCs. In one aspect, the UE further transmits, at a second stage, a second coefficient selection bitmap indicating, for each NZC location indicated in the first coefficient selection bitmap, a corresponding NZC location in a time domain. In another aspect, the UE further transmits, at a second stage, a second coefficient selection bitmap indicating, for each subset in each time domain basis of a three-dimensional bitmap and that is associated with one of a first domain or a second domain, whether an NZC is located in the subset.