Visible-Light Wireless Communication Using Segmented LED Frequency Bands
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Solution Overview
Problem
The bandwidth and wavelength characteristics of white LEDs with yellow phosphor, which have a slow decay rate, limit the available frequency band in visible-light communication systems, resulting in a narrower frequency bandwidth for yellow light compared to blue light.
Innovation Solution
A visible-light wireless communication system utilizing multiple light transmitters capable of generating light signals modulated in different frequency bands, including white LEDs with phosphor coatings for yellow, green, or red light, and a frequency converter to control and combine these signals for enhanced frequency modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If white LED with yellow phosphor is used as light transmitter, then manufacturing cost is reduced and ease of manufacture is improved, but frequency bandwidth is narrowed due to slow decay rate
Solution Approach 1:
The patent divides the frequency bandwidth into multiple segments by using multiple white LEDs with different phosphor materials (yellow, green, red phosphors) that each operate in different frequency bands. This segmentation allows the system to overcome the bandwidth limitation of individual LEDs while maintaining the cost-effectiveness of using white LEDs with phosphor coatings.
Solution Approach 2:
The patent combines multiple light signals from different white LEDs (with yellow, green, and red phosphors) into a composite light signal that covers a wider frequency bandwidth. The combining process integrates the strengths of each LED type while maintaining cost-effectiveness, as each individual LED still uses the economical phosphor coating approach.
2Ease of manufacture
If yellow phosphor is coated on blue light active layer, then manufacturing cost is reduced, but decay rate becomes slow and frequency bandwidth is limited
Solution Approach 1:
The patent changes the parameter of phosphor type across multiple LEDs, using yellow phosphor for some LEDs (slower decay), green phosphor for others (intermediate decay), and red phosphor for others (faster decay). This parameter variation allows the system to achieve both cost-effectiveness and improved overall bandwidth by selecting appropriate phosphor types for different frequency band segments.
3Device complexity
If single light transmitter is used, then device complexity is reduced, but transmission data capacity is limited
Solution Approach 1:
The patent extends the system from a single-dimensional (single LED) to a multi-dimensional configuration by adding multiple white LEDs with different phosphor characteristics. This dimensional expansion in the frequency domain enables higher transmission data capacity while managing device complexity through systematic arrangement and control of the multiple LEDs.
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 increases the transmission data capacity by maintaining an open eye diagram from 10 Mbps to 40 Mbps, compared to conventional systems, effectively expanding the usable frequency band and improving communication efficiency.
Implementation Method 1
a plurality of light transmitters for generating light signals modulated in different frequency bands for wireless communication with the terminals
Implementation Method 2
a white LED in which yellow phosphor is coated on an active layer capable of generating blue light
Data Source
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AI summary
A visible-light wireless communication system includes a plurality of light transmitters for generating light signals modulated at different frequencies and at least one terminal for wirelessly communicating with the plurality of light transmitters using the light signals.