MIMO Beamforming Matrix Feedback Bandwidth Reduction

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Solution Overview

Problem

Closed loop MIMO systems require significant bandwidth for transmitting channel state information, which reduces the available bandwidth for data traffic and increases decoding complexity.

Innovation Solution

The beamforming matrix V is represented using N2−N real numbers instead of 2N2 real numbers by factoring out non-essential phase information and discarding it prior to quantization, reducing the feedback bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If channel state information is transmitted using the full beamforming matrix V (2N² real numbers), then accurate beamforming can be achieved, but feedback bandwidth is consumed

Engineering Contradiction:

Improvebeamforming accuracyVSAvoidfeedback bandwidth

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent extracts and discards the non-essential phase information from each column of the beamforming matrix V, retaining only the magnitude information. This reduces the feedback data from 2N² real numbers to N² real numbers, effectively halving the feedback bandwidth requirement while preserving the essential beamforming characteristics.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent discards the phase information that cannot be recovered at the transmitter, and recovers only the necessary magnitude information. By factoring out the phase components e^(jθ_n) from each column and discarding them, the system recovers and transmits only the magnitude values |v_n1|, |v_n2|, ..., |v_nN|, which are sufficient for beamforming reconstruction.

Inventive Principle:

Principle #34Discarding and recovering

2Reliability

If full channel state information is fed back, then beamforming performance is maintained, but available bandwidth for data traffic is reduced

Engineering Contradiction:

Improvebeamforming performanceVSAvoiddata traffic bandwidth

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent separates the beamforming matrix V into magnitude and phase components, extracting only the magnitude information |v_nm| for feedback. This extraction process removes the unnecessary phase information that would consume bandwidth, allowing more bandwidth to be allocated to data traffic while maintaining beamforming performance through the recovered magnitude information.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If complete beamforming matrix information is transmitted, then accurate channel compensation is achieved, but decoding complexity increases

Engineering Contradiction:

Improvechannel state accuracyVSAvoiddecoding complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the magnitude information from the beamforming matrix, reducing the amount of data that needs to be processed and decoded. By removing the phase information that adds complexity without providing additional channel state accuracy, the decoding complexity at the transmitter is significantly reduced while maintaining the precision needed for channel compensation.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS7492829B2Closed loop feedback in MIMO systems

Publication Date: 2009.02.17 INTEL CORP

AI summary

Feedback bandwidth may be reduced in a closed loop MIMO system by factoring non essential information out of a beamforming matrix.