Downlink Interference Alignment With Constant Amplitude Codebooks

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Solution Overview

Problem

Current downlink interference alignment techniques in radio communication systems require significant bandwidth for channel state information (CSI) feedback from user equipment (UEs) to base stations, reducing available data transmission bandwidth and complexity in managing interference.

Innovation Solution

Implementing a constant amplitude codebook for CSI feedback, which transmits only phase information, reducing the number of bits required for feedback and enabling more efficient downlink interference alignment, while also supporting user selection scheduling and rate balancing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional CSI feedback schemes are used to enable downlink interference alignment, then channel state information accuracy is improved, but bandwidth consumption for feedback increases

Engineering Contradiction:

Improvechannel state information accuracyVSAvoidbandwidth consumption

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential phase information from the complete channel state information, discarding the amplitude components. This is achieved through constant amplitude codebooks where UEs quantize and feedback only phase values, reducing feedback bandwidth while maintaining sufficient accuracy for interference alignment operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the parameter representation by using constant amplitude codebooks that quantify channel phase information rather than transmitting full complex CSI. This parameter transformation reduces the feedback dimension from magnitude-phase pairs to phase-only values, achieving bandwidth reduction while preserving interference alignment performance.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If full channel state information is fed back from UEs to base stations, then interference alignment performance is improved, but available data transmission bandwidth is reduced

Engineering Contradiction:

Improveinterference alignment performanceVSAvoiddata transmission bandwidth

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent extracts only the phase information from complete channel state information, discarding amplitude components. Constant amplitude codebooks enable UEs to quantize and feedback only phase values, reducing feedback bandwidth consumption while maintaining sufficient accuracy for interference alignment operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent transforms the CSI representation by using constant amplitude codebooks that quantify phase information rather than transmitting full complex CSI. This parameter transformation reduces feedback dimension from magnitude-phase pairs to phase-only values, achieving bandwidth reduction while preserving interference alignment performance.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If detailed channel information is transmitted for interference alignment, then signal quality is improved, but system complexity increases

Engineering Contradiction:

Improvesignal qualityVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential phase information from complete channel state information, discarding amplitude components. This is achieved through constant amplitude codebooks where UEs quantize and feedback only phase values, reducing feedback bandwidth while maintaining sufficient accuracy for interference alignment operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8744473B2Downlink limited-feedback interference alignment with constant amplitude codebooks and rate balance scheduling

Publication Date: 2014.06.03 VIVO MOBILE COMM CO LTD

AI summary

Downlink interference alignment schemes are described which provide, among other things, channel state information (CSI) from the UEs using a constant amplitude codebook. By providing only phase information associated the UEs' channel states, instead of both amplitude and phase information, fewer bits can be used to inform the BSs of the UEs effective channels, thereby reducing the bandwidth requirements associated with the transmission of CSI by UEs for downlink interference alignment purposes. According to other embodiments, feedback information can be used to perform user selection scheduling and rate balancing.