Non-Uniform Constellation Modulation for Phase Noise Robustness
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Solution Overview
Problem
Current communication systems using uniform constellations face limitations in maximizing coding and modulation capacity while maintaining reduced bit error rates and robustness against phase noise, particularly in channels with high signal-to-noise ratios and phase noise conditions.
Innovation Solution
The implementation of non-uniform constellations (NUCs) optimized for specific channel conditions, featuring quadrant and octant symmetry, which are designed to maximize BICM capacity and robustness against phase noise, with constellation points strategically located to achieve improved performance across various code rates and noise conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform constellations are used, then device complexity is reduced and ease of manufacture is improved, but coding and modulation capacity is limited and bit error rate is higher
Solution Approach 1:
The patent applies asymmetry by transitioning from uniform constellations (symmetric, equally spaced points) to non-uniform constellations (asymmetric, optimally spaced points). The constellation points are strategically positioned at different distances from the origin and with varying angular separations to maximize coding and modulation capacity while maintaining robustness against phase noise. This asymmetric arrangement allows better exploitation of signal space without proportionally increasing implementation complexity.
2Productivity
If non-uniform constellations are used, then coding and modulation capacity is increased, but device complexity increases
Solution Approach 1:
The patent applies local quality by optimizing different regions of the constellation diagram with different properties. Inner constellation points are positioned to maximize distance from origin for robustness, while outer points are arranged to maximize angular separation for capacity. Each region of the constellation is locally optimized for its specific function, achieving global performance improvement without requiring complex overall restructuring.
Solution Approach 2:
The patent changes the parameters of constellation points (amplitude, phase, spacing) to optimize performance. By varying the distance of points from the origin and their angular positions, the system achieves higher coding and modulation capacity. The non-uniform spacing and amplitude levels are carefully selected parameters that maximize capacity while keeping the modulation scheme practical to implement.
3Device complexity
If uniform constellations are used, then implementation is simpler, but robustness against phase noise is reduced
Solution Approach 1:
The patent applies preliminary action by pre-positioning constellation points at optimal locations before transmission. The non-uniform constellation is designed in advance with points strategically placed to maximize robustness against expected phase noise conditions. This preliminary optimization of point positions ensures that the signal is inherently more resistant to phase noise without requiring complex real-time correction mechanisms.
Data Source
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AI summary
A coding and modulation apparatus and method are presented, particularly for use in a system according to IEEE 802.11. The apparatus comprises an encoder configured to encode input data into cell words according to an LDPC code and a modulator configured to modulate said cell words into constellation values of a non-uniform constellation and to assign bit combinations to constellation values of the used non-uniform constellation. The modulator is configured to use a non-uniform constellation and bit labeling from one of the several groups of constellations, which constellation show quadrant and octant symmetry.