Visible Light Communication Using Spatial Multiplexing to Reduce LED Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing visible ray communication systems face challenges in achieving high data transmission speed and quality due to the high Peak to Average Power Ratio (PAPR) associated with Orthogonal Frequency-Division Multiplexing (OFDM), which requires a light-emitting device to handle a wide dynamic range, making it difficult and costly to implement with conventional LEDs.
Innovation Solution
A visible ray communication system that uses a plurality of light-emitting devices, a Serial-to-Parallel converter, a modulator, a carrier signal multiplier, and a light-emitting control unit to generate and control transmission signals, allowing for spatial multiplexing and demodulation without requiring a high dynamic range from the light-emitting devices, thereby reducing the performance demands on the LEDs and driving circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM is applied to visible ray communication to improve frequency use efficiency and communication quality, then communication performance is improved, but Peak to Average Power Ratio (PAPR) is increased requiring high dynamic range
Solution Approach 1:
The patent divides the single high-dynamic-range transmission channel into multiple parallel low-dynamic-range channels by separating the OFDM signal into multiple data streams. Each stream is modulated onto a different carrier frequency and transmitted through a separate LED. This segmentation allows each LED to operate with a limited dynamic range while collectively achieving the frequency multiplexing benefits of OFDM.
Solution Approach 2:
The patent transitions from time-domain multiplexing (single LED transmitting OFDM signal over time) to frequency-domain spatial multiplexing (multiple LEDs transmitting simultaneously on different carrier frequencies). By adding the spatial dimension with multiple light-emitting devices, the system achieves OFDM-like frequency efficiency without the high PAPR burden on individual devices.
2Productivity
If a light-emitting device handles a wide dynamic range signal to achieve high data transmission speed, then data transmission speed is improved, but the light-emitting device requires special elements and becomes costly
Solution Approach 1:
The patent segments the high-speed data transmission task across multiple conventional LEDs rather than relying on a single specialized high-performance light-emitting device. Each LED handles a portion of the data stream at a lower speed, but the aggregate throughput achieves high data transmission rates. This allows the use of standard, cost-effective LED components throughout the system.
Solution Approach 2:
The patent uses multiple copies of conventional LED devices instead of a single specialized high-performance device. By replicating standard LEDs and coordinating their operation through parallel data streams and frequency division, the system achieves high transmission speeds using inexpensive, readily available components rather than costly specialized elements.
3Speed
If a single light-emitting device transmits high-speed data, then data transmission speed is improved, but the device structure becomes complex requiring special elements
Solution Approach 1:
The patent divides the high-speed transmission function across multiple simple light-emitting devices rather than concentrating it in one complex device. Each LED maintains a simple structure while the system as a whole achieves high speed through parallel processing of multiple data streams on different carrier frequencies.
Solution Approach 2:
The patent merges the transmission capabilities of multiple simple LED devices to achieve the performance of a single complex high-speed device. By combining parallel data streams from multiple LEDs and using frequency division multiplexing at the receiver, the system achieves high-speed transmission while keeping individual device structures simple and conventional.
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 improves communication performance and quality similar to OFDM, while allowing the use of conventional, less expensive LEDs and driving circuits, reducing manufacturing costs and enabling efficient frequency use without the need for high dynamic range capabilities.
Implementation Method 1
a plurality of light-emitting devices; a light-emitting control unit for illuminating the plurality of light-emitting devices according to the N transmission signals
Implementation Method 2
a light-receiving device for receiving lights, the lights being emitted from the plurality of light-emitting devices of the transmission apparatus and spatially multiplexed in a transmission medium, thereby outputting reception signals according to corresponding reception intensities
Data Source
AI summary
Disclosed is a visible ray communication system including a transmission apparatus and a reception apparatus, wherein the transmission apparatus includes: a plurality of light emitting devices; an S/P converter for serial-to-parallel converting transmission data, thereby generating N data streams; a modulator for modulating the generated N data streams for respective carriers with a predetermined number of dimensions, thereby generating N modulated signals; a carrier signal multiplier for multiplying the generated N modulated signals by orthogonal N carrier signals, respectively, thereby generating N transmission signals; and a light emitting control unit for illuminating the plurality of light emitting devices according to the generated N transmission signals.