Uplink MIMO Aperture Constraint for 5G NR Feedback Overhead

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Solution Overview

Problem

Current MIMO codebook designs for 5G NR uplink face challenges in balancing high resolution for better performance with the increased feedback overhead, particularly when DL/UL reciprocity is non-ideal, leading to significant SRS transmission and feedback overhead.

Innovation Solution

The implementation of aperture constraints to limit uplink precoder candidates by restricting anchor beam selections or improving beam resolution within a constrained angular region, reducing feedback overhead and enhancing spatial resolution through two-stage codebook design and oversampling adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high resolution codebook design is used for better MIMO performance, then beamforming performance is improved, but feedback overhead increases significantly

Engineering Contradiction:

Improvebeamforming performanceVSAvoidfeedback overhead

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The codebook is divided into two stages (W1 and W2) where W1 provides coarse beam selection and W2 provides fine beam refinement. This segmentation allows the system to achieve high resolution beamforming performance while limiting the feedback overhead by only requiring feedback of the W2 index, which has fewer candidates due to the aperture constraint on W1.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The aperture constraint applies a local quality improvement by concentrating the codebook resolution within a restricted angular region (aperture) rather than distributing it across the entire angular space. This allows high beamforming precision within the aperture while reducing the overall codebook size and feedback requirements.

Inventive Principle:

Principle #3Local quality

2Loss of information

If aperture constraint is applied to limit precoder candidates, then feedback overhead is reduced, but codebook design complexity increases

Engineering Contradiction:

Improvefeedback overheadVSAvoidcodebook design complexity

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The aperture constraint parameters are configured dynamically based on channel conditions and network requirements. The gNB can adjust the aperture angle and other codebook parameters adaptively, allowing the system to optimize the trade-off between feedback overhead and beamforming performance according to current operational conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes key codebook parameters including aperture angle, oversampling factor, and codebook granularity to control the number of precoder candidates. By adjusting these parameters, the system can flexibly control feedback overhead while maintaining adequate beamforming performance for different deployment scenarios.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10461823B2Aperture constraint for new radio uplink multiple-input multiple-output

Publication Date: 2019.10.29 NOKIA TECHNOLOGIES OY

AI summary

Systems, methods, apparatuses, and computer program products relating to support MIMO on the UL with flexibility and enhanced performance, for example, in 5G or new radio access technology (NR).