MIMO Radio DMRS Phase Shifting for Lower PAPR

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Solution Overview

Problem

The increased Peak-to-Average-Power-Ratio (PAPR) in multiple input multiple output (MIMO) radio systems due to coherent addition of demodulation reference signal (DMRS) symbols limits the ability to support high spectral efficiencies and quadrature amplitude modulation schemes, leading to reduced coverage and signal distortion.

Innovation Solution

A modified cyclic delay diversity (CDD) method is applied, introducing a phase rotation per physical resource block group to mitigate PAPR without increasing delay spread or computational complexity, maintaining MIMO performance and quasi co-location properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple CDM groups are used to support more than two layers in MIMO, then the system can support higher layer counts and spectral efficiency, but the PAPR of DMRS symbols increases due to coherent addition of layer time domain signals

Engineering Contradiction:

Improvesupport for more than two layersVSAvoidPAPR increase

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by introducing a cyclic delay parameter 'm' that varies across different CDM groups. Specifically, for the first CDM group, a first cyclic delay value is applied, while for the second CDM group, a second cyclic delay value is applied. This differential parameter adjustment prevents coherent alignment of DMRS symbols from different layers, thereby reducing PAPR while maintaining support for multiple layers.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If PA power is reduced to handle increased PAPR, then the system can avoid signal distortion and clipping, but coverage is reduced and higher order QAM schemes cannot be supported

Engineering Contradiction:

Improveavoid signal distortionVSAvoidcoverage area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent converts the harmful effect of coherent addition (which causes high PAPR) into a beneficial outcome by intentionally introducing cyclic delays that misalign the signals. This transformation allows the system to maintain high PA power operation while avoiding distortion, as the cyclic delays prevent the coherent addition that would otherwise require power reduction.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Object-affected harmful factors

If conventional CDD is applied to reduce PAPR, then PAPR is reduced, but delay spread increases which may impact channel estimation and computational complexity increases

Engineering Contradiction:

ImprovePAPR reductionVSAvoidcomputational complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies local quality by differentiating the cyclic delay values across different CDM groups rather than applying a uniform delay. Each CDM group receives a specific cyclic delay value tailored to its characteristics. This localized approach reduces PAPR effectively while minimizing the overall delay spread impact, as only the necessary delays are applied to specific groups rather than universally.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20250293731A1Peak to average power reduction in multiple input multiple output (MIMO) radio

Publication Date: 2025.09.18 INTEL CORP

AI summary

A wireless communication device comprising a processor, configured to determine a first signal corresponding to a resource block group; determine a phase shift; shift a second signal by the phase shift; control a transmitter to transmit the first signal and the phase shifted second signal during a transmission time corresponding to the resource block group.