NR Type II CSI Feedback Using Angle and Delay Reciprocity

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Solution Overview

Problem

The overhead and computational complexity of New Radio (NR) Type II channel state information (CSI) feedback are high due to the need for extensive reporting of frequency-domain basis vectors and linear combination coefficients, especially in FDD operations, which limits efficient precoding in wireless communication systems.

Innovation Solution

Utilizing angle and delay reciprocity to predetermine a subset of frequency-domain basis vectors and jointly encoding selected spatial-domain and frequency-domain basis pairs with CSI-RS ports, reducing the feedback overhead and computational complexity at the wireless device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If extensive reporting of frequency-domain basis vectors and linear combination coefficients is performed for NR Type II CSI feedback, then precoding accuracy is improved, but feedback overhead and computational complexity increase

Engineering Contradiction:

Improveprecoding accuracyVSAvoidfeedback overhead

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for precoding by reporting selected spatial-domain and frequency-domain basis vector indices rather than full basis vectors. This selective extraction maintains precoding accuracy while significantly reducing feedback overhead by transmitting only the critical identification parameters.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the CSI feedback into distinct components: spatial-domain basis vector selection, frequency-domain basis vector selection, and linear combination coefficients. This segmentation allows each component to be optimized independently, reducing overall complexity while maintaining the precision benefits of Type II codebook.

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

Engineering Contradiction:

Improveprecoding accuracyVSAvoidcomputational complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary action by pre-defining the codebook structure with fixed spatial and frequency-domain basis vectors at the transmitter. This allows the receiver to simply select and report indices rather than compute full basis vectors, significantly reducing computational complexity while maintaining precoding accuracy through the pre-configured codebook design.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies partial action by reporting only the necessary subset of information (selected basis vector indices and their combination coefficients) rather than complete channel state information. This partial reporting provides sufficient precision for effective precoding while avoiding the computational burden of processing and transmitting full channel matrices.

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If Type II CSI feedback is used to achieve high data rates, then spectral efficiency is improved, but feedback overhead increases

Engineering Contradiction:

Improvedata rateVSAvoidfeedback overhead

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent uses copying by transmitting indices that reference pre-defined basis vectors in the codebook rather than transmitting the actual basis vectors themselves. This indirect copying approach maintains the precision needed for high data rates while dramatically reducing feedback overhead by sending only compact index identifiers.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent segments feedback into compact index reports for spatial and frequency domain selections plus concise coefficient information. This segmentation enables high data rate performance through precise precoding while minimizing feedback overhead by transmitting only the essential segmented components rather than complete channel information.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12567891B2Methods for reducing overhead of NR type II channel state information feedback using angle and delay reciprocity

Publication Date: 2026.03.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method, network node and wireless device for reducing overhead of New Radio (NR) Type II channel state information (CSI) feedback using angle and delay reciprocity are disclosed. According to one aspect, a method in a wireless device (WD) includes receiving a configuration of CSI report setting that indicates frequency domain basis vectors from a discrete Fourier transform, CSI reference signal (RS) ports and a subset of pairs of spatial domain and frequency domain vectors for the NCSI-RS CSI-RS ports. The method also includes determining linear combination coefficients corresponding to the selected frequency domain basis vectors and the selected subset of CSI-RS ports, determining linear combination coefficients corresponding to the selected frequency domain basis vectors and the selected subset of pairs of vectors in the spatial domain and the frequency domain.