Type-II CSI Codebook Restriction for Lower Subband Feedback Overhead

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Solution Overview

Problem

The existing 3GPP Rel.-15 Type-II CSI reporting scheme for New Radio (NR) wireless communication systems faces high feedback overhead due to the increased reporting of combining coefficients on a subband basis, which becomes significant for large numbers of subbands.

Innovation Solution

A method and apparatus for channel state information (CSI) feedback in wireless communication systems, utilizing a three-stage precoder matrix structure that includes a first codebook for spatial beam components and a second codebook for delay components, with optimized configurations and reporting of beam and delay vectors to reduce feedback overhead.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Type-II CSI reporting is used with subband-based combining coefficients, then measurement precision is improved, but feedback overhead increases significantly

Engineering Contradiction:

ImproveCSI reporting accuracyVSAvoidfeedback overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent segments the codebook into two independent parts: a first codebook for spatial beam components and a second codebook for delay components. This segmentation allows the UE to report only the indices of selected codebook entries rather than full combining coefficients for all subbands, significantly reducing feedback overhead while maintaining CSI accuracy through the structured combination of spatial and delay information.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts and reports only the essential information needed for precoding - the indices of selected codebook entries - rather than transmitting all combining coefficient values. By taking out only the codebook indices and allowing the gNB to reconstruct the precoder using the codebook structure, the feedback overhead is dramatically reduced while preserving measurement precision.

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If the number of subbands is increased, then measurement precision is improved, but feedback overhead increases linearly

Engineering Contradiction:

ImproveCSI resolutionVSAvoidfeedback overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent segments the feedback into spatial beam selection (first codebook) and delay selection (second codebook) components. This segmentation enables the system to handle increased numbers of subbands by reporting only the indices of relevant codebook entries rather than full coefficient data for each subband, thus maintaining precision while controlling overhead growth.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the reporting parameter from full combining coefficients to codebook indices. This parameter change fundamentally alters the feedback structure, allowing the system to scale with the number of subbands by reporting only the indices of selected codebook entries rather than transmitting all coefficient values, thereby controlling feedback overhead while maintaining measurement precision.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If three-stage precoder structure is used, then device complexity is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improveprecoder structure complexityVSAvoidcodebook configuration accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent segments the precoder into three functional stages: first stage for spatial beam selection, second stage for delay selection, and third stage for combining. This segmentation simplifies the overall device complexity by breaking down the precoder into manageable components with specific functions, making the system more implementable while maintaining the precision requirements through structured codebook configuration.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20250357989A1Methods and Apparatuses for Codebook Restriction for Type-II Feedback Reporting and Higher Layer Configuration and Reporting for Linear Combination Codebook in a Wireless Communications Network

Publication Date: 2025.11.20 KONINKLIJKE PHILIPS NV

AI summary

Method performed by a UE for providing a channel state information (CSI) feedback in a wireless communication system including at least the UE and a gNB or a radio network node. The UE is operative to: estimate the MIMO channel between the gNB and the UE based on received DL reference signals for the configured resource blocks. The UE is further operative to calculate, based on a performance metric, a precoder matrix, for a number of antenna ports of the gNB and configured subbands, the precoder matrix being based on two codebooks and a set of combination coefficients for complex scaling/combining one or more of vectors selected from a first codebook and a second codebook, and the UE is operative to report a CSI feedback and/or a PMI and/or a PMI/RI, to the gNB, used to indicate the precoder matrix for the configured antenna ports and resource blocks.