Visible Light OFDM Transmission Using IFFT Pulse Sampling
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Solution Overview
Problem
The application of the OFDM scheme in light communication is hindered by the requirement for light-emitting elements and driving circuits with high dynamic range and linearity, which are costly to produce and not feasible with existing infrastructure.
Innovation Solution
A visible light communication apparatus and method that employs a Serial-to-Parallel converter, modulation means, and Inverse Fast Fourier Transform (IFFT) to generate orthogonal modulation signals, using square waves to reduce the need for high dynamic range and linearity in light-emitting elements, and arranges carrier signals to avoid harmonic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the OFDM scheme is applied to light communication to improve communication quality and transmission speed, then frequency use efficiency and multipath tolerance are improved, but the requirement for light-emitting elements and driving circuits with large dynamic range and high linearity increases, making implementation costly and impractical
Solution Approach 1:
The patent transforms the continuous OFDM signal into a discrete pulse signal by sampling the IFFT output at specific time points. This parameter transformation changes the signal characteristics from requiring continuous high-linearity modulation to using discrete pulse positioning, which can be generated by simple switching circuits rather than high-linearity modulators, thereby reducing implementation cost while maintaining transmission speed.
Solution Approach 2:
The patent replaces the traditional analog OFDM modulation system with a digital pulse generation system. Instead of using analog modulators that require high linearity and large dynamic range, the system uses digital switching to generate pulse signals directly from the IFFT output samples, substituting complex analog circuitry with simpler digital logic that is easier and cheaper to manufacture.
2Reliability
If special LEDs and special LED driving circuits with large dynamic range and high linearity are implemented to enable OFDM scheme, then communication quality is improved, but production cost becomes even more expensive than usual LEDs and driving circuits
Solution Approach 1:
The patent uses standard, off-the-shelf LEDs and driving circuits that are inexpensive and widely available, rather than requiring specialized high-performance components. By transforming the signal format to discrete pulses and using simple switching to drive the LEDs, the system achieves reliable communication quality using cheap, mass-produced components that can be easily manufactured and replaced.
Solution Approach 2:
The patent employs a switching circuit that automatically selects between different IFFT output samples based on timing signals, eliminating the need for complex analog modulation circuits. The system uses simple digital switching logic to generate the modulated signal, allowing standard LEDs to be driven effectively without requiring specialized high-linearity driving circuits, thereby reducing production cost while maintaining communication quality.
3Adaptability or versatility
If existing lighting infrastructure is used for light communication, then ease of deployment is improved, but the lack of large dynamic range and high linearity in conventional LEDs and driving circuits prevents OFDM scheme implementation
Solution Approach 1:
The patent makes the OFDM-based light communication system compatible with universal, standard LED lighting infrastructure. By transforming the continuous OFDM signal into discrete pulses that can be generated by simple switching circuits driving standard LEDs, the system achieves multi-functionality where existing lighting infrastructure can be used for both illumination and communication without requiring specialized high-linearity components, thereby improving ease of deployment while managing device complexity through signal transformation.
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 configuration allows for effective use of OFDM carriers to improve transmission speed without requiring expensive special light-emitting elements or driving circuits, reducing production costs and enabling practical implementation of the OFDM scheme in light communication.
Implementation Method 1
a light-emitting means for causing a light source to emit light based on the IFFT signal generated by the IFFT means
Data Source
AI summary
Disclosed is an apparatus and a method for transmitting data by using visible light. The transmission apparatus includes: a Serial-to-Parallel (S/P) converter for performing a Serial-to-Parallel conversion on transmission data, and generating multiple parallel data; a modulation means for modulating the multiple parallel data generated by the S/P converter, and generating multiple modulation signals; an Inverse Fast Fourier Transform (IFFT) means for performing an IFFT on the multiple modulation signals so that the multiple modulation signals are orthogonal to one another, and generating an IFFT signal; and a light-emitting means for causing a light source to emit light based on the IFFT signal generated by the IFFT means.