Downlink Channel Estimate Compression for Low-Overhead CSI Feedback

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Solution Overview

Problem

Current methods for conveying downlink channel estimates in 3GPP networks face challenges such as high uplink overhead, limited accuracy due to channel reciprocity issues, and inefficiencies in CSI feedback, particularly in FDD deployments and scenarios with large antenna arrays, which hinder advanced MIMO precoding and beamforming techniques.

Innovation Solution

A method involving the use of compression functions and decompression functions, comprising linear and non-linear components, to efficiently compress and reconstruct downlink channel estimates at the terminal device and network node, respectively, allowing for reduced overhead and improved channel state information accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If downlink channel estimates are transmitted with high accuracy using traditional methods, then channel state information accuracy is improved, but uplink overhead increases significantly

Engineering Contradiction:

Improvechannel state information accuracyVSAvoiduplink overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts and transmits only the most significant components of channel state information (singular vectors and singular values) rather than complete channel estimates. This selective extraction reduces uplink overhead while maintaining sufficient accuracy for MIMO precoding operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the representation parameters of channel state information by using singular value decomposition to transform channel matrices into a compact form with fewer parameters (singular vectors and values). This parameter transformation enables reduced overhead transmission while preserving essential channel characteristics.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If complete channel estimates are fed back to the network node, then channel state information accuracy is improved, but uplink overhead and transmission time increase

Engineering Contradiction:

Improvechannel state information accuracyVSAvoidfeedback time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent extracts only the essential components needed for MIMO precoding (singular vectors and dominant singular values) and transmits them to the network node. This extraction approach reduces feedback time by eliminating unnecessary data transmission while maintaining the accuracy required for effective precoding operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies partial action by transmitting a subset of channel state information parameters that are sufficient for MIMO precoding rather than complete channel estimates. This partial feedback approach reduces transmission time while providing adequate information for network node processing.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If channel reciprocity is assumed for channel estimation, then uplink overhead is reduced, but measurement precision deteriorates due to non-ideal reciprocity conditions

Engineering Contradiction:

Improveuplink overheadVSAvoidchannel estimate accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical assumption of channel reciprocity with a signal processing approach using singular value decomposition. Instead of relying on reciprocity conditions, the system processes uplink reference signals through SVD to extract accurate channel components, thereby maintaining precision without requiring ideal reciprocity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the estimation parameters by using singular value decomposition to identify and extract the most significant channel components from uplink reference signals. This parameter transformation enables accurate channel estimation even when reciprocity conditions are not perfectly met, as the SVD process naturally filters out noise and non-reciprocal components.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11509363B2Compression and decompression of downlink channel estimates

Publication Date: 2022.11.22 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A network node (501) determines parameters (503) indicating a compression function for compressing downlink channel estimates, and a decompression function. The network node transmits the parameters, receives compressed downlink channel estimates (504), and decompresses the compressed downlink channel estimates using the decompression function. A terminal device (502) receives the parameters, forms the compression function, compresses downlink channel estimates using the compression function, and transmits the compressed downlink channel estimates. The compression function comprises a first function formed based on at least some of the parameters, a second function which is non-linear, and a quantizer. The first function is configured to receive input data, and to reduce a dimension of the input data. The decompression function comprises a first function configured to receive input data and provide output data in a higher dimensional space than the input data, and a second function which is non-linear.