Hybrid QAM APSK Modulation for Microwave Link PAPR Reduction

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Solution Overview

Problem

High-order modulation schemes in point-to-point microwave communication links are susceptible to additive white Gaussian noise (AWGN) and phase noise, leading to performance degradation due to high Peak-to-Average Power Ratio (PAPR).

Innovation Solution

A hybrid modulation scheme combining Quadrature Amplitude Modulation (QAM) and Amplitude Phase Shift Keying (APSK) is proposed, where bits are mapped to a hybrid constellation with QAM and APSK points, optimizing constellation point arrangement to reduce PAPR and phase noise sensitivity while maintaining performance similar to QAM under AWGN.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high order modulation is used to improve spectral efficiency, then spectral efficiency is improved, but the system becomes more sensitive to AWGN, phase noise and PAPR

Engineering Contradiction:

Improvespectral efficiencyVSAvoidperformance under AWGN, phase noise and PAPR

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent combines QAM and APSK modulation schemes into a hybrid modulation scheme that merges the high spectral efficiency of QAM with the robustness of APSK against phase noise and PAPR, achieving both high productivity and reliability simultaneously

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The hybrid constellation is constructed as a composite structure with inner QAM points and outer APSK points, analogous to composite materials that combine different properties to achieve superior overall performance compared to single-material solutions

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If QAM modulation is used due to its robust performance to AWGN and ease of implementation, then ease of operation and reliability under AWGN are improved, but the system suffers from high PAPR and sensitivity to phase noise

Engineering Contradiction:

Improveease of implementation and AWGN performanceVSAvoidPAPR and phase noise sensitivity

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The hybrid constellation applies different modulation characteristics to different regions: inner points use QAM-like properties for AWGN robustness while outer points use APSK-like properties for reduced PAPR and phase noise immunity, optimizing local qualities for different operational conditions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the constellation parameters by combining two different modulation schemes with distinct parameter characteristics, transforming the single-parameter optimization of pure QAM into multi-parameter optimization that balances PAPR, phase noise sensitivity, and AWGN performance

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11196598B1Modulation scheme for high order constellation

Publication Date: 2021.12.07 HUAWEI TECH CANADA CO LTD

AI summary

Aspects of the present application provide methods and devices for using a combined QAM and APSK modulation scheme in a hybrid modulation form in order to benefit from advantages of each respective modulation scheme. The proposed hybrid modulation scheme is less sensitive to phase noise and has lower PAPR than QAM and has very similar performance as QAM with respect to AWGN.