Space-Delay Precoding Structure for Low-Feedback MIMO Beamforming

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Solution Overview

Problem

Existing wireless communication systems face significant challenges in reducing feedback overhead associated with precoding, particularly in multi-antenna systems, which can lead to increased computational complexity and inefficiencies.

Innovation Solution

Implementing a dual-stage space-delay precoding structure that includes a spatial codebook matrix and a frequency-domain codebook matrix, where each vector is associated with a delay or delay difference, and a combining element for complex scaling/combining, allowing for reduced feedback by exploiting specific advantages of different precoders for various transmission ranks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If conventional precoding is used in multi-antenna systems, then communication performance is maintained, but feedback overhead increases significantly

Engineering Contradiction:

Improvefeedback overheadVSAvoidsystem complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The patent segments the precoding process into two distinct stages: wideband precoding for spatial dimension and subband precoding for frequency dimension. This segmentation allows feedback to be provided separately for each stage, reducing the overall feedback overhead compared to conventional single-stage precoding while maintaining communication performance through the structured dual-stage approach

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a dual-stage structure that adds a temporal dimension to the precoding process by separating wideband and subband operations. This dimensional separation enables more efficient feedback mechanisms where only essential parameters need to be fed back at each stage, rather than complete precoding matrices, thus reducing feedback overhead

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If feedback overhead is reduced, then system complexity decreases, but mutual information and rate performance deteriorate

Engineering Contradiction:

Improvesystem complexityVSAvoidmutual information and rate

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary wideband precoding before subband processing, where the wideband stage establishes optimal spatial beamforming based on long-term channel statistics. This preliminary action captures the dominant spatial characteristics that persist across frequency, allowing reduced feedback in subsequent subband stages while maintaining mutual information through the pre-established spatial structure

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the feedback parameters from complete precoding matrices to reduced sets of parameters that define the dual-stage precoders. By parameterizing the precoding structure to exploit channel correlations across frequency and space, the system maintains rate performance with fewer feedback parameters, thus reducing complexity without sacrificing reliability

Inventive Principle:

Principle #35Parameter changes

3Loss of information

If conventional precoding is used at mmWave frequencies, then channel coverage is maintained, but feedback overhead increases due to sparse channel characteristics

Engineering Contradiction:

Improvefeedback overheadVSAvoidchannel coverage

Core Design Contradiction:

Loss of informationVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by treating wideband and subband channels differently according to their specific characteristics. The wideband stage handles the sparse mmWave channel structure with robust spatial beamforming, while the subband stage adapts to frequency-specific variations. This localized treatment of different channel domains reduces feedback overhead by focusing feedback on the most critical parameters for each stage rather than uniform feedback across all frequencies

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12621023B2Receiver, transmitter, system and method employing space-delay precoding

Publication Date: 2026.05.05 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A receiver processes a radio signal received via a radio channel from a transmitter employing a plurality of antenna ports, determines complex precoder coefficients and delays of one or more space-delay precoders for one or more transmission layers and antenna ports at the transmitter so as to achieve a predefined property for a communication over the radio channel, and feeds back, explicitly or implicitly, delays and the complex precoder. The space-delay precoder has a dual-stage structure having a spatial codebook matrix including spatial beamforming vectors, a frequency-domain codebook matrix, and a combining element per layer for complex scaling or combining one or more of the vectors selected from the spatial and/or frequency-domain codebook matrices. The frequency-domain codebook matrix is defined by a sub-matrix of a DFT matrix, which the sub-matrix of the DFT matrix is associated with a range of delay values.