Visible Light Communication Apparatus Using Pulse Position Modulation
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Solution Overview
Problem
Existing visible light communication systems using LED illumination struggle to synchronize brightness control with data transmission, leading to inefficiencies and reduced communication speed due to the interference between pulse width modulation (PWM) signals for brightness control and modulation signals for communication.
Innovation Solution
A visible light communication apparatus and method that utilizes a 2 pulse position modulation (2PPM) scheme, where the duty cycle of the PWM signal is maintained constant, and the position of the ON section pulse is adjusted based on transmission data, ensuring that the brightness control and communication functions are not affected, allowing for synchronized data transmission without altering the number of transmittable bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM scheme is used to control LED brightness, then brightness control efficiency and precision are improved, but visible light communication function is hindered due to collision with modulation signals
Solution Approach 1:
The patent segments the PWM period into multiple sub-periods, with each sub-period capable of carrying independent communication data. This segmentation allows the brightness control function to be maintained at the PWM level while communication data is embedded within the sub-periods, resolving the conflict between brightness control and communication functionality.
Solution Approach 2:
The patent merges the brightness control signal and communication modulation signal into a unified PWM-driven LED control system. By combining both functions into a single integrated approach where communication data modulates the PWM signal structure rather than competing with it, the system achieves simultaneous brightness control and visible light communication.
2Adaptability or versatility
If PWM signal and modulation signal are combined, then both brightness control and communication are enabled, but synchronization becomes difficult and transmission speed varies
Solution Approach 1:
The patent applies preliminary action by pre-defining the PWM duty cycle and period parameters before communication data transmission. The communication data is then mapped to specific sub-periods within the predetermined PWM framework, ensuring synchronization is established in advance and transmission speed remains stable without real-time adjustments.
3Illumination intensity
If LED turn on/off time is changed to control brightness, then brightness is adjusted, but communication data transmission accuracy is affected
Solution Approach 1:
The patent applies local quality by maintaining different characteristics within different parts of the PWM cycle. The overall PWM duty cycle determines brightness (global property), while local sub-periods within the PWM cycle encode communication data with precise timing (local property). This allows brightness adjustment without compromising the precision of communication data transmission in the local sub-periods.
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
Enables effective visible light communication while maintaining brightness control, ensuring consistent communication speed and preventing interference between brightness control and data transmission, thus overcoming the limitations of existing systems.
Implementation Method 1
an illumination that is operated according to the driving signal from the illumination driver
Implementation Method 2
The visible light (visible rays) is an area of an electromagnetic wave that is visible to human sight
Data Source
AI summary
The visible light communication apparatus includes: a brightness signal generator that calculates a duty cycle of an driving signal corresponding to brightness requirement information and generates clock frequency information on brightness signals based on the calculated duty cycle; a transmission data generator that generates transmission data; an illumination driver that generates and outputs an driving signal in a pulse waveform based on the clock frequency information of the brightness signals and the transmission data and controls a pulse position of a turn on section for each bit unit time in the waveform of the driving signal based on the transmission data; and an illumination that is operated according to the driving signal from the illumination driver.