Explicit MIMO CSI Feedback via Time-Domain Tap Selection

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Solution Overview

Problem

Existing Multiple-Input-Multiple-Output (MIMO) wireless communication systems face high feedback overhead and inter-stream user interference due to low-resolution channel state information (CSI) feedback, especially in Cloud RAN environments, where CSI varies slowly and explicit calibration methods require full channel matrix acquisition.

Innovation Solution

A method and system for enabling explicit CSI feedback in MIMO wireless communication systems, where user equipment receives downlink CSI, generates explicit CSI, and transmits it back to base stations, using inverse discrete Fourier Transform and quantization to reduce feedback overhead by focusing on significant time domain channel taps and interpolating CSI values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If low resolution quantization is used for channel matrix feedback, then feedback overhead is reduced, but inter stream-user interference increases

Engineering Contradiction:

Improvefeedback overheadVSAvoidinter stream-user interference

Core Design Contradiction:

Loss of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent replaces traditional frequency-domain quantization methods with time-domain processing. By applying inverse DFT to convert frequency-domain channel coefficients to time-domain impulse response, the system can identify and retain only significant channel taps, achieving compression without substantial quality loss. This substitution of domain (frequency to time) enables more efficient feedback while maintaining channel state accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts only the significant channel taps from the full channel impulse response after inverse DFT transformation. By identifying and retaining only the dominant time-domain coefficients that contribute meaningfully to channel characteristics, the system eliminates redundant feedback data while preserving essential channel state information, thereby reducing overhead without proportionally increasing interference.

Inventive Principle:

Principle #2Taking out (Extraction)

2Measurement precision

If CSI is feedback for every subcarrier, then channel accuracy is improved, but feedback overhead increases significantly

Engineering Contradiction:

Improvechannel accuracyVSAvoidfeedback overhead

Core Design Contradiction:

Measurement precisionVSLoss of substance

Solution Approach 1:

The patent transforms the feedback approach from frequency-domain per-subcarrier reporting to time-domain impulse response feedback. By applying inverse DFT to aggregate channel coefficients across subcarriers and identifying significant time-domain taps, the system captures essential channel characteristics with far fewer feedback parameters, achieving compression while maintaining accuracy for channels with limited delay spread.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of feedback for every subcarrier, the patent uses partial action by selecting and feedback only the significant channel taps that contribute meaningfully to channel state. This selective approach provides sufficient channel accuracy for MIMO processing while dramatically reducing feedback overhead compared to complete per-subcarrier feedback.

Inventive Principle:

Principle #16Partial or excessive action

3Loss of substance

If sub-band grouping is used for CSI feedback, then feedback overhead is reduced, but inter stream-user interference increases due to low resolution

Engineering Contradiction:

Improvefeedback overheadVSAvoidinter stream-user interference

Core Design Contradiction:

Loss of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent replaces sub-band frequency-domain grouping with time-domain impulse response analysis. By transforming channel coefficients through inverse DFT and identifying significant taps across the entire bandwidth, the system captures essential channel characteristics without being constrained by sub-band boundaries, achieving better interference mitigation while maintaining reduced feedback overhead.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10873370B2Method and system for enabling explicit channel state information (CSI) feedback in multiple-input-multiple-output (MIMO)

Publication Date: 2020.12.22 WISIG NETWORKS PTE LTD

AI summary

Embodiments of the present disclosure discloses a method for enabling CSI feedback in Multiple Input Multiple Output (MIMO) wireless communication system comprising at least one user equipment (UE) and at least one base station (BS). The UE receives a plurality of downlink (DL) channel state information CSI from the BS and generate an explicit CSI from the received DL CSI. The UE determines a range of frequency domain values and channel state values from the received DL CSI. Upon determination, the UE performs IDFT to determine time domain channel impulse response matrices for the range of frequency domain values and perform CSI quantization. In another embodiment, the processor performs CSI quantization on either full range or a partial range of the time domain channel impulse response matrices to obtain optimized time domain channel explicit CSI and transmit the generated explicit CSI as a feedback to the one or more BS.