Precoder Matrix Decomposition for 5G CSI Feedback Overhead
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Solution Overview
Problem
The high feedback overhead in Channel State Information (CSI) reporting for beamforming in 5G wireless communications networks, particularly due to the large number of subbands, leads to inefficiencies in precoder feedback, which existing technologies have not adequately addressed.
Innovation Solution
The method involves decomposing each combining coefficient of the precoder matrix into amplitude and phase components, separately quantizing and reporting these components with minimal bits, and using decomposition schemes to reduce the number of reported coefficients, thereby reducing feedback overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual-stage precoding with per-subband beam-combining coefficients is used for accurate CSI reporting, then beamforming precision is improved, but feedback overhead increases linearly with the number of subbands
Solution Approach 1:
The patent segments the feedback information by separating wideband amplitude coefficients (reported once for all subbands) from subband-specific phase coefficients. This segmentation allows the system to maintain precise beamforming across all subbands while reducing redundant feedback, as the amplitude information which is common across subbands is reported only once rather than repeated for each subband.
Solution Approach 2:
The patent extracts and reports only the essential subband-specific information (phase coefficients) separately from the wideband common information (amplitude coefficients). By taking out only the varying phase components for subband-specific reporting while relying on the already-reported amplitude values, the feedback overhead is significantly reduced while maintaining the precision needed for accurate beamforming adaptation per subband.
2Adaptability or versatility
If all beam-combining coefficients are reported for every subband, then beamforming adaptability is improved, but feedback overhead becomes unmanageably large
Solution Approach 1:
The patent applies local quality by differentiating the reporting strategy between amplitude coefficients (reported with wideband quality for all subbands) and phase coefficients (reported with subband-specific quality). This allows the system to maintain high adaptability where needed (phase information per subband) while reducing overhead in areas where full adaptability is less critical (amplitude information common across subbands), achieving an optimized balance between adaptability and feedback efficiency.
Data Source
AI summary
The invention relates to a method performed by a combination of a radio network node, a network node, and a user equipment (device) for reducing s feedback overhead. The method performed by the user equipment (device) decomposes each entry corresponding to a (i,j)-th combining coefficient of a precoder matrix into at least two coefficients then quantizing, each of the at least two coefficients and reporting information related to at least one phase value or at least one amplitude value of the quantized coefficients.