Non-Uniform Constellation Modulation for Low-SNR Error Reduction
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Solution Overview
Problem
Current coding and modulation systems in communications face challenges in maximizing capacity and reducing bit error rates while operating at reduced signal-to-noise ratios, particularly in non-uniform constellations which are not optimized for varying code rates and channel characteristics.
Innovation Solution
The implementation of a coding and modulation apparatus that uses non-uniform constellations (NUCs) optimized based on code rates and channel characteristics, allowing for dynamic reduction of constellation points to enhance performance without compromising decoding complexity, and incorporating predistortion to counteract transmission system non-linearities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform constellations are used in coding and modulation systems, then the system structure is simple and easy to implement, but the capacity is not maximized and bit error rate is high at reduced SNR
Solution Approach 1:
The patent applies asymmetry by transitioning from uniform constellations with equal spacing to non-uniform constellations where constellation points are asymmetrically positioned based on code rate and channel characteristics. This asymmetric arrangement optimizes the distribution of points to maximize capacity and minimize bit error rate at reduced SNR, directly resolving the contradiction between implementation simplicity and system reliability.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting constellation parameters (spacing, positioning, distribution) according to code rate and channel conditions. Instead of fixed uniform spacing, the constellation points are repositioned based on operational parameters, enabling the system to adapt to varying channel characteristics and maximize performance without compromising implementation feasibility.
2Reliability
If non-uniform constellations optimized for specific code rates are used, then capacity is maximized and bit error rate is reduced, but the system complexity increases
Solution Approach 1:
The patent applies dynamics by making the constellation configuration adaptive rather than static. The non-uniform constellation parameters are dynamically selected based on the code rate and channel characteristics, allowing the system to optimize performance for different operating conditions without requiring a completely different system design. This dynamic adaptation resolves the contradiction by enabling high performance across multiple scenarios while maintaining a unified system architecture.
Solution Approach 2:
The patent manages complexity through controlled parameter changes where only specific constellation parameters are adjusted based on code rate and channel conditions, while the overall system structure remains consistent. This selective parameter optimization allows the system to achieve maximum capacity and minimum bit error rate without fundamentally increasing system complexity, as the changes are confined to the constellation mapping layer.
3Productivity
If constellation points are densely packed to increase capacity, then more data can be transmitted, but the system becomes more sensitive to noise and interference
Solution Approach 1:
The patent applies local quality by creating non-uniform spacing where different regions of the constellation have different point densities. Rather than uniform packing throughout, the constellation points are strategically positioned with varying density in different areas, allowing high capacity regions to be optimized for data transmission while other regions provide robustness against noise and interference. This local optimization resolves the contradiction between capacity and noise sensitivity.
Data Source
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AI summary
A coding and modulation apparatus and method are presented. The apparatus comprises an encoder that encodes input data into cell words, and a modulator that modulates said cell words into constellation values of a non-uniform constellation. The modulator is configured to use, based on the total number M of constellation points of the constellation and the code rate, a non-uniform constellation from one or several groups of constellations each comprising one or more constellations.