Visible Light Transmission Using 3D Color Space Modulation
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Solution Overview
Problem
Existing visible light communication systems face challenges in improving reception quality and transmission speeds due to limitations in modulation and demodulation techniques, particularly when using light sources that need to maintain perceptible brightness for their primary functions.
Innovation Solution
A transmission device that modulates light based on two- or three-dimensional color space mapping and a reception device that demodulates signals symbol-by-symbol in the same space, utilizing CMOS sensors for high-speed signal capture and employing modulation schemes like 4 PPM to ensure minimal perceptible flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visible light communication uses traditional modulation techniques, then the light source can maintain perceptible brightness, but transmission speed and reception quality are limited
Solution Approach 1:
The patent transitions from traditional one-dimensional intensity modulation to two-dimensional color space modulation by mapping signal points onto a color space constellation. This dimensional expansion allows simultaneous encoding of multiple data bits per symbol while maintaining light intensity within perceptible ranges, thereby improving transmission speed without sacrificing reception quality
Solution Approach 2:
The invention changes the modulation parameters by using color space coordinates (e.g., CIE xy chromaticity coordinates) instead of traditional amplitude or frequency parameters. By varying color coordinates while keeping overall luminance relatively constant, the system achieves higher data rates with minimal perceptible flicker, resolving the contradiction between speed and quality
2Productivity
If visible light communication increases transmission speed, then data transfer rate improves, but reception quality deteriorates
Solution Approach 1:
By mapping modulation symbols to two-dimensional color space rather than traditional one-dimensional amplitude modulation, the system can encode more bits per symbol (higher data rate) while maintaining sufficient signal-to-noise margin in each dimension, thus preserving reception quality even at increased speeds
Solution Approach 2:
The patent performs preliminary signal point mapping in color space before modulation, optimizing the constellation arrangement to maximize distance between adjacent signal points. This pre-optimization ensures that even at high transmission speeds where noise impact increases, the receiver can still accurately distinguish between different symbols, maintaining reception quality
3Productivity
If light source modulation depth increases for faster communication, then transmission speed improves, but perceptible flicker increases
Solution Approach 1:
The invention changes from amplitude-based modulation to color-coordinate-based modulation. By varying the chromaticity coordinates (x, y) while maintaining relatively constant luminance (Y), the system achieves high-speed communication through color changes that are less perceptible to the human eye, thus reducing flicker while improving communication speed
Solution Approach 2:
The patent explicitly uses color space modulation where different signal points correspond to different color coordinates. This allows data encoding through subtle color variations rather than gross intensity changes, enabling faster modulation rates without creating perceptible flicker, as the human eye is less sensitive to color changes than brightness changes
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
Enhances reception quality and transmission speeds in visible light communication by optimizing modulation and demodulation processes, allowing for faster data transfer without compromising the functionality of the light source.
Implementation Method 1
a transmission device modulates the strength of light emitted from a light-emitting element such as an LED (light emitting diode) based on transmission data, and transmits a signal by changing the brightness of the emitted light
Implementation Method 2
a light receiver generates a reception signal by receiving an optical signal via a plurality of light receiving elements
Data Source
AI summary
A transmission device includes a symbol generator that generates a modulation symbol by mapping transmission data to a signal point arranged in a two-dimensional or three-dimensional color space; and an outputter that outputs an optical signal modulated according to the modulation symbol.