5G CSI Precoder Quantization for Lower Beamforming Feedback
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Solution Overview
Problem
The high feedback overhead in Channel State Information (CSI) reporting for beamforming in 5G networks, particularly due to the large number of beam-combining coefficients in the second-stage precoder, necessitates efficient quantization and reporting methods to reduce communication overhead.
Innovation Solution
Decompose each combining coefficient of the precoder matrix into multiple components, separately quantize these components, and report only the non-zero coefficients using bitmaps or strongest coefficients, along with configurable parameters to minimize feedback bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-stage precoding with second-stage precoder F2 is used for beamforming, then communication link adaptation and performance are improved, but feedback overhead increases approximately linearly with the number of subbands
Solution Approach 1:
The patent segments the second-stage precoder F2 into two distinct components: a wideband amplitude matrix FA that is common across all subbands, and subband-specific complex coefficients f2 that contain only the subband-dependent information. This segmentation allows the amplitude information to be reported once for all subbands while only the varying phase and magnitude adjustments need to be reported per subband, thereby reducing the total feedback overhead while maintaining the adaptive beamforming capability.
2Measurement precision
If the number of beam-combining coefficients in F2 is increased to improve CSI accuracy, then channel state information precision is improved, but feedback overhead becomes considerably large
Solution Approach 1:
The patent extracts the wideband amplitude information from the subband-specific coefficients and places it into a separate wideband amplitude matrix FA. By taking out this common amplitude component, the remaining subband-specific coefficients f2 only need to represent the variations in amplitude and phase for each subband, significantly reducing the number of bits required for feedback while preserving the essential CSI accuracy for beamforming adaptation.
3Reliability
If all subband-dependent coefficients are reported to maintain precoding accuracy, then beamforming performance is maintained, but communication efficiency decreases due to large feedback overhead
Solution Approach 1:
The patent segments the feedback information into wideband amplitude components (reported once) and subband-specific complex coefficients (reported per subband). This segmentation enables the system to maintain beamforming performance by preserving the essential subband variations while improving communication efficiency by avoiding redundant transmission of common amplitude information across all subbands.
Data Source
AI summary
The invention describes a method performed by a radio network node, a network node, a method performed by a UE and a UE for reducing s feedback overhead. The method performed by the UE is decomposing each entry corresponding to a combining coefficient of a precoder matrix into at least two coefficients and quantizing, separately, each of two coefficients with a least one bit, and reporting information related to a phase value or an amplitude value or at a phase value and an amplitude value of the quantized coefficient.