Visible Light Communication SNR Improvement via Dimmer Synchronization
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Solution Overview
Problem
Current visible light communication (VLC) systems face challenges in achieving a high signal-to-noise ratio (SNR) due to low modulation levels, leading to errors in signal detection and interpretation, while also needing to avoid flicker that is discernable to the human eye.
Innovation Solution
The system includes a controller that adjusts the dimming level of the dimmer in synchronization with the modulation circuit's visible light signal, allowing for increased modulation levels up to 10% of the power signal's amplitude, thereby enhancing the SNR without causing noticeable flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If modulation levels are increased to improve SNR, then signal detection reliability is improved, but visible flicker is generated that is discernable to the human eye
Solution Approach 1:
The system uses periodic modulation of the light output at frequencies above human visual perception (typically >200Hz) to encode data. By operating in the periodic domain at high frequencies, the modulation becomes imperceptible to humans while still providing sufficient signal variation for reliable detection by photodetectors, thus resolving the contradiction between detectability and invisibility.
Solution Approach 2:
The system changes the frequency parameter of the light modulation to exceed human visual detection thresholds. By adjusting the modulation frequency to be in the ultraviolet or high-visible range that human eyes cannot detect, the system achieves high SNR for machine detection while maintaining imperceptibility for human observers, effectively resolving the flicker visibility issue.
2Object-affected harmful factors
If modulation levels are kept low to avoid visible flicker, then human comfort is maintained, but signal-to-noise ratio deteriorates leading to detection errors
Solution Approach 1:
The system employs high-frequency periodic modulation that creates sufficiently large signal variations for reliable detection while remaining above the human visual detection threshold. The periodic nature at frequencies >200Hz ensures both adequate SNR for photodetector detection and imperceptibility to human eyes, simultaneously achieving reliable detection and flicker avoidance.
Solution Approach 2:
The system transitions from spatial/temporal modulation at visible frequencies to temporal modulation at ultraviolet or high-frequency visible ranges. By changing the frequency dimension beyond human visual perception, the system achieves adequate signal strength for detection while the modulation remains invisible to humans, resolving the contradiction between detection reliability and flicker avoidance.
3Use of energy by moving object
If dimming is applied to reduce light output, then energy consumption is reduced, but VLC signal quality deteriorates
Solution Approach 1:
The system superimposes high-frequency periodic modulation on the dimmed light output. Even at reduced average power levels, the periodic modulation creates sufficient instantaneous signal variations that maintain adequate SNR for detection. The high-frequency carrier ensures that the modulated signal remains detectable despite overall power reduction, allowing energy-efficient operation without sacrificing VLC signal quality.
Solution Approach 2:
The system changes the modulation frequency parameter to a level where the modulated signal maintains sufficient amplitude even at reduced power settings. By operating at high frequencies with appropriate modulation depth, the system ensures that the signal-to-noise ratio remains adequate for reliable detection even when average power is reduced through dimming, thus maintaining VLC quality while reducing energy consumption.
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 improves the reliability of VLC signal detection and interpretation by increasing the SNR while maintaining imperceptible flicker, enabling more accurate data transmission through visible light communication.
Implementation Method 1
a light source, operatively coupled to the driver circuit and the modulation circuit, that receives the output of the driver circuit and the visible light signal and generates, using the output of the driver circuit and the visible light signal, a light output comprising a visible light communication (VLC) signal
Data Source
Figure 1
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Figure 3A~3C
AI summary
A method of increasing modulation of a visible light signal. The method can include receiving a signal that corresponds to the visible light signal, where the visible light signal has a magnitude. The method can also include adjusting, by a controller and based on the signal, a dimmer level of a dimmer by an amount, where the amount is proportional to the magnitude of the visible light signal, and where the dimmer level adjusts an output of a driver circuit. The visible light signal and the output of the driver circuit can be combined into a power signal and sent to one or more light sources. The one or more light sources can use the power signal to generate a light output that includes a visible light communication signal that is received by a receiver.