Beamforming Coefficients via Smooth Unitary Matrix

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Solution Overview

Problem

Existing beamforming methods for MIMO wireless communications, such as SVD and MMSE, suffer from adverse effects like reduced coherence bandwidth and increased spatial peak-to-average ratio, which negatively impact performance.

Innovation Solution

The method determines beamforming coefficients using a smooth unitary matrix approach, specifically calculating W=HH(HHH)^(-1/2), which avoids these limitations and maintains the combined channel's delay spread, similar to SVD, while ensuring equal strength across streams.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If SVD beamforming is used, then beamforming performance is improved, but coherence bandwidth is reduced

Engineering Contradiction:

Improvebeamforming performanceVSAvoidcoherence bandwidth

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the mathematical parameters of beamforming from SVD decomposition to QR decomposition, transforming the beamforming matrix calculation method. This parameter change maintains beamforming performance while preserving coherence bandwidth by avoiding the rank-reduction effect of SVD.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses QR decomposition as an alternative mathematical approach that copies the essential functionality of SVD beamforming (signal enhancement and spatial filtering) while avoiding its detrimental effects on coherence bandwidth through a different decomposition methodology.

Inventive Principle:

Principle #26Copying

2Reliability

If MMSE beamforming is used, then beamforming performance is improved, but spatial peak-to-average ratio increases

Engineering Contradiction:

Improvebeamforming performanceVSAvoidspatial peak-to-average ratio

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent changes the beamforming calculation from MMSE optimization to QR decomposition, fundamentally altering the mathematical approach. This parameter change reduces spatial peak-to-average ratio by avoiding the aggressive beam focusing that MMSE employs, while maintaining acceptable beamforming performance.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If SVD beamforming is used, then beamforming performance is improved, but delay spread is decreased

Engineering Contradiction:

Improvebeamforming performanceVSAvoiddelay spread

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent changes the beamforming mathematical model from SVD to QR decomposition, which alters how the beamforming matrix interacts with the channel impulse response. This parameter change preserves delay spread characteristics by maintaining the full rank structure of the channel matrix.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7693551B2Derivation of beamforming coefficients and applications thereof

Publication Date: 2010.04.06 BELL NORTHERN RESEARCH LLC

AI summary

A method for determining beamforming coefficients begins by obtaining channel information for a multiple tone communication. The method then continues by deriving the beamforming coefficients based on the channel information and a smoothness criteria.