Probabilistic Shaped QAM Using Phase Modulation to Cut DM Complexity
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Solution Overview
Problem
Current quadrature amplitude modulation (QAM) systems based on probabilistic shaping (PS) face complexity and inefficiency due to the complexity of the distribution matching (DM) encoding process, which increases with input data volume, affecting modulation and demodulation processes.
Innovation Solution
The proposed solution combines DM encoding with easy-to-implement phase modulation, replacing direct DM encoding to reduce mapping depth and complexity, and incorporates binary labeling and forward error correction to improve efficiency and applicability of QAM signal modulation and demodulation methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct DM encoding is performed on N1 first bits to obtain N2 first symbols, then spectral efficiency is improved, but mapping depth and system complexity sharply increase
Solution Approach 1:
The patent segments the N1 input bits into two groups: N1-N3 bits for amplitude modulation and N3 bits for phase modulation. This segmentation allows the complex DM encoding to be applied only to the amplitude components rather than the entire symbol stream, thereby reducing mapping depth while maintaining spectral efficiency improvements from probabilistic shaping.
Solution Approach 2:
The patent extracts the phase modulation component from the overall modulation process. By separating phase-modulated symbols (with preset signal power) from amplitude-modulated symbols, the system applies DM encoding only where necessary for spectral efficiency, avoiding the complexity increase that would result from applying it uniformly across all symbols.
2Device complexity
If DM encoding complexity is reduced by combining with phase modulation, then system complexity is lowered, but spectral efficiency improvement may be compromised
Solution Approach 1:
The patent applies different modulation qualities to different symbol types: amplitude-modulated symbols receive full DM encoding treatment for maximum spectral efficiency, while phase-modulated symbols use simpler encoding with preset power. This local differentiation maintains spectral efficiency where it matters most while reducing overall system complexity.
Solution Approach 2:
Instead of applying DM encoding to all symbols (excessive action), the patent applies it partially only to amplitude-modulated symbols. This partial application is sufficient to achieve spectral efficiency improvements while avoiding the complexity penalty of universal application.
3Ease of manufacture
If conventional QAM modulation is used, then implementation is simple, but transmission capacity is limited
Solution Approach 1:
The patent merges conventional QAM modulation simplicity with probabilistic shaping capabilities by combining amplitude modulation (with DM encoding for capacity improvement) and phase modulation (for spectral efficiency). This hybrid approach maintains implementation feasibility while significantly increasing transmission capacity through shaped amplitude distribution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a less complex and highly efficient QAM signal modulation method with improved applicability, enabling faster demodulation speeds and increased network transmission capacity.
Implementation Method 1
a quadrature amplitude modulation (QAM) system (hereinafter referred to as a PS-QAM system) based on probabilistic shaping (PS) is proposed
Implementation Method 2
phase modulation is performed on the N4 to-be-phase-modulated symbols based on N3 second bits, to obtain N4 second symbols
Implementation Method 3
binary labeling (BL) encoding is performed on the N4 second symbols and N2-N4 first symbols in the N2 first symbols except the N4 to-be-phase-modulated symbols
Implementation Method 4
forward error correction (FEC) encoding is performed on the N5 BL encoded output bits, to obtain N6 FEC redundant bits
Data Source
AI summary
The present disclosure relates to modulation methods. One example method includes performing distribution matching (DM) encoding on N1 first bits to obtain N2 first symbols, determining N4 to-be-phase-modulated symbols whose signal powers are equal to a preset signal power from the N2 first symbols, performing phase modulation on the N4 to-be-phase-modulated symbols based on N3 second bits to obtain N4 second symbols, performing binary labeling (BL) encoding on the N4 second symbols and N2-N4 first symbols to obtain N5 BL encoded output bits, performing forward error correction (FEC) encoding on the N5 BL encoded output bits to obtain N6 FEC redundant bits, and performing quadrature amplitude modulation (QAM) mapping based on the N6 FEC redundant bits and the N5 BL encoded output bits to obtain N2 target QAM signals.