Optical Wireless Communication Using Variable Pulse Position Modulation
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Solution Overview
Problem
Existing optical wireless communication systems face challenges in efficiently decoding composite waveforms, which consist of a lower frequency time varying amplitude component and a high data rate pulse position modulated component, especially in asynchronous communication scenarios where the data rate timing clocks are not frequency synchronous.
Innovation Solution
The system employs a composite waveform with a lower frequency time varying amplitude component for quick identification of modulated light sources and a high data rate VPPM component using variable pulse position modulation, allowing for efficient decoding by a camera operating at low and high frequencies through region-of-interest subsampling and Start Frame Delimiter (SFD) synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high data rate VPPM component is used for data transmission, then the data transmission rate is improved, but the complexity of decoding the composite waveform increases
Solution Approach 1:
The composite waveform is segmented into two distinct components: a lower frequency time varying amplitude component for identification purposes and a high data rate VPPM component for data transmission. This segmentation allows the receiving system to process each component separately, reducing the overall decoding complexity while maintaining high data transmission rates
Solution Approach 2:
The lower frequency amplitude component serves as an intermediary that facilitates the decoding process by providing a simplified identification signal. This intermediary component allows the receiver to establish initial synchronization and identify modulated light sources before attempting to decode the more complex high-rate VPPM data, thereby reducing the effective decoding complexity
2Adaptability or versatility
If asynchronous communication is used to improve flexibility, then the adaptability is improved, but the difficulty of detecting and measuring data timing increases
Solution Approach 1:
The system performs preliminary actions by using the lower frequency amplitude component to establish initial timing reference and synchronization before the high-rate VPPM data transmission begins. This preliminary timing establishment simplifies the subsequent detection and measurement of asynchronous data timing, reducing the difficulty of timing detection
Solution Approach 2:
The composite waveform structure enables self-service timing detection where the amplitude component inherently provides timing information that assists in synchronizing the detection of the VPPM component. The waveform essentially provides its own timing reference, reducing the external assistance needed for timing detection in asynchronous communication
Data Source
AI summary
Optical wireless communication techniques are described and claimed. In one embodiment, the disclosure relates to method and apparatus to provide optical signaling with visible light having variable pulse position modulation (VPPM). The optical signal includes a Start Frame Delimiter (SFD) which indicates beginning of an asynchronous optical signaling. The VPPM signaling includes a lower frequency time varying amplitude component that when subsampled by a low frame rate camera results in alias induced flicker or blinking. Such signals are quickly recognizable as signals with modulated data. In another embodiment, the disclosure provides a system, device and method for decoding a Start Frame Delimiter (SFD) to indicate arrival of incoming VPPM optical data.