Hybrid Precoding Matrix for MIMO Power Reduction

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Solution Overview

Problem

Conventional hybrid beamforming methods in massive MIMO systems fail to guarantee per data stream Quality of Service (QoS) requirements while minimizing transmit power, often requiring excessive power due to approximations in RF precoders and combiners that do not accurately represent the eigenvectors of the effective channel gain matrix.

Innovation Solution

The method involves obtaining a hybrid precoding matrix using dominant right and left eigenvectors of the effective channel matrix, combining digital and analog precoding, and combining matrices to accurately represent both phase and amplitude information, thereby maximizing channel gains and minimizing transmit power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional hybrid beamforming methods use RF precoders and combiners with only exponential entries to approximate eigenvectors, then device complexity is reduced, but manufacturing precision deteriorates because amplitudes of eigenvectors are ignored and only phase information is utilized

Engineering Contradiction:

ImproveRF precoder and combiner structureVSAvoideigenvector representation accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent combines digital baseband precoding matrices with analog RF precoding matrices to form a hybrid precoding matrix, similarly combining different types of matrix operations (digital and analog) to achieve both accuracy and feasibility. This composite approach allows the system to utilize the precision of digital processing while incorporating the hardware-friendly analog phase shifters.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent divides the precoding process into two separate stages: baseband digital precoding and RF analog precoding. The baseband precoding matrix handles amplitude and phase information digitally, while the RF precoding matrix focuses on phase adjustment through analog phase shifters. This segmentation allows each component to optimize for its specific function.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If conventional hybrid beamforming approximates eigenvectors using only phase information, then ease of operation is improved, but loss of information occurs because amplitude information is ignored resulting in small sub-channel gains

Engineering Contradiction:

Improvebeamforming implementationVSAvoidamplitude information

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The baseband precoding matrix acts as an intermediary that processes signals before they reach the RF precoders. It compensates for the amplitude information loss by performing digital signal processing that restores the amplitude characteristics that would otherwise be lost in the analog phase-shifting stage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent performs baseband digital precoding before the RF analog precoding stage. This preliminary digital processing prepares the signals with proper amplitude and phase relationships, which are then maintained through the RF stage. The preliminary action ensures that amplitude information is preserved before the analog stage that would otherwise discard it.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If conventional hybrid beamforming increases transmit power to compensate for low sub-channel gains, then reliability is improved, but use of energy deteriorates due to excessive power consumption

Engineering Contradiction:

ImproveQoS guaranteeVSAvoidtransmit power

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the approach from adjusting transmit power to adjusting the precoding matrices themselves. By optimizing the baseband and RF precoding matrices to accurately represent eigenvectors, the system achieves higher sub-channel gains without increasing power. This parameter change shifts the optimization from power level to signal processing parameters.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs iterative algorithms that use feedback from channel state information to optimize the precoding matrices. The system continuously adjusts the baseband and RF precoding matrices based on feedback about the effective channel conditions, ensuring optimal performance without excessive power consumption.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11258498B2Hybrid beamforming in communication systems

Publication Date: 2022.02.22 SHARAFAT AHMAD REZA

AI summary

A method for hybrid digital-analog beamforming a communication system. The method includes obtaining a plurality of transmit phase shifted signals by obtaining a hybrid precoding matrix FH. The hybrid precoding matrix FH is obtained based on a plurality of dominant right eigenvectors of a first effective channel matrix associated with a set of wireless channels. The hybrid precoding matrix FH includes a product of a digital precoding matrixFB⁢B(1)and an analog precoding matrix FRF. Each entry of the analog precoding matrix FRF includes one of zero or a respective complex value with unit magnitude. Obtaining the plurality of transmit phase shifted signals further includes obtaining a digital precoding matrixFB⁢B(2)based on the hybrid precoding matrix FH. Each wireless channel in the set of wireless channels is associated with a base station and a respective user equipment (UE) in a set of UEs.