Visible Light WDM Signaling for White Color Balance
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Solution Overview
Problem
In visible light communication systems using wavelength division parallel transmission, energy imbalances among wavelengths lead to color tone deviations from white, causing issues in signal transmission and reception, especially when the system is affected by time-varying channels.
Innovation Solution
A method and apparatus that involve inverting and delaying signals to correct energy differences among wavelengths by transmitting both original and inverted signals, and using diversity techniques to ensure balanced energy distribution, allowing for accurate restoration and channel decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple LEDs for generating three primary colors (RGB) are used to achieve high-speed transmission, then transmission speed is improved, but energy distribution among wavelengths becomes unbalanced causing color tone deviation from white
Solution Approach 1:
The patent applies inversion by transmitting both original and inverted signals through different wavelengths. Specifically, one wavelength transmits the original signal while another wavelength transmits the inverted signal (where 1 becomes 0 and 0 becomes 1). This complementary transmission ensures that energy is balanced across wavelengths, maintaining white light color balance while achieving high-speed parallel transmission.
2Productivity
If wavelength division parallel transmission is used to increase transmission capacity, then productivity is improved, but energy imbalance among wavelengths causes color tone changes
Solution Approach 1:
The patent divides transmission capacity across multiple wavelengths in parallel, with each wavelength carrying either original or inverted signals. This wavelength division approach increases overall transmission capacity while the inversion technique ensures that energy distribution remains balanced, preventing color tone changes and maintaining white light quality.
3Device complexity
If original signal only is transmitted to simplify system configuration, then device complexity is reduced, but reliability is decreased due to time-varying channel effects
Solution Approach 1:
The patent applies local quality by assigning different signal characteristics to different wavelengths. Specifically, one wavelength transmits the original signal while another wavelength transmits the inverted signal. This differentiation allows the receiver to use diversity combining techniques to combat time-varying channel effects, improving reliability without significantly increasing overall system complexity.
Solution Approach 2:
The system uses feedback through diversity combining at the receiver end. By receiving both original and inverted signals through different wavelengths and combining them appropriately, the system compensates for channel variations and improves transmission reliability.
Data Source
AI summary
Disclosed is a method and an apparatus for correcting a color imbalance of visible light in wavelength division parallel visible light communications. The method includes the steps of: inverting an original signal including information by a visible light communication transmitter; transmitting the original signal including the information and an inverted signal from the visible light communication transmitter to a visible light communication receiver, receiving the original signal including the information and the inverted signal by the visible light communication receiver, reinverting the inverted signal among the received signals by the visible light communication receiver, restoring the inverted signal back to its state prior to the inversion by reinverting the inverted signal by the visible light communication receiver, and performing a diversity combination on the original signal and a restored signal.