Undersampled FSK VLC for Indoor Navigation
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Solution Overview
Problem
Existing communication technologies face challenges in transmitting data through light sources without causing perceivable flicker to the human eye and efficiently decoding data using low sampling rates, particularly in indoor navigation applications.
Innovation Solution
The method involves varying the frequency of an amplitude-modulated light source, such as an LED, to encode data, which is then received and decoded by a device with a low sampling frequency, like a smartphone camera, using frequency shift keying (FSK) modulation, ensuring the flicker is not noticeable and allowing for indoor navigation and communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light source is modulated at high frequency to transmit data, then the data transmission rate is improved, but the flicker becomes perceivable to the human eye
Solution Approach 1:
The patent applies parameter changes by modulating the light source at frequencies that are integer multiples of the camera's sampling rate (e.g., 60Hz, 120Hz, 180Hz). This specific frequency selection causes the modulated light to appear stationary or non-flickering to the human eye while still enabling efficient data extraction through undersampling at the camera's lower sampling rate. The frequency parameter is carefully chosen to balance communication efficiency with human visual comfort.
2Measurement precision
If the camera sampling rate is increased to accurately capture the modulated light, then the data reception accuracy is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies partial action through undersampling technology. Instead of requiring the camera to sample at the full modulation frequency (which would be necessary for complete signal reconstruction), the system deliberately samples at a lower rate (e.g., 60Hz when modulating at 120Hz or 180Hz). This partial sampling approach, combined with frequency-shift keying, enables accurate data recovery without requiring high sampling rates, thus reducing device complexity and power consumption.
Solution Approach 2:
The patent uses frequency-shift keying as an intermediary mechanism. By encoding data through frequency shifts (e.g., 0Hz for '0', 60Hz for '1') rather than direct amplitude modulation, the system creates a frequency-domain representation that can be extracted through undersampling. The frequency shifting acts as a mediator that bridges the gap between the modulation frequency and the camera's sampling capability, enabling accurate data reception at lower sampling rates.
3Productivity
If the modulation frequency is set to match the camera sampling rate, then the data can be extracted through undersampling, but the flicker becomes noticeable to humans
Solution Approach 1:
The patent applies periodic action by using frequency-shift keying with periodic frequency transitions. The modulation frequency is set to an integer multiple of the sampling rate (e.g., 2× or 3×), creating a periodic pattern that repeats consistently with the sampling cycle. This periodicity enables efficient data extraction through undersampling while the specific frequency multiple ensures the flicker remains imperceptible to humans, as the modulation occurs at frequencies above the human visual threshold or in sync with the camera's frame rate.
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 enables wireless communication and indoor navigation by allowing data to be transmitted and received through modulated light sources without perceivable flicker, utilizing low sampling rates effectively, and facilitating applications like smart shopping and location determination.
Implementation Method 1
varying a frequency of an amplitude-modulated light source to generate light and receiving the data by undersampling frequencies of modulation of the light
Implementation Method 2
frequency shift on-off keying (UFSOOK)
Data Source
AI summary
Embodiments may provide a way of communicating via an electromagnetic radiator, or light source, that can be amplitude modulated such as light emitting diode (LED) lighting and receivers or detectors that can determine data from light received from the amplitude modulated electromagnetic radiator. Some embodiments may provide a method of transmitting/encoding data via modulated LED lighting and other embodiments may provide receiving/decoding data from the modulated LED lighting by means of a device with a low sampling frequency such as a relatively inexpensive camera (as might be found in a smart phone). Some embodiments are intended for indoor navigation via photogrammetry (i.e., image processing) using self-identifying LED light anchors. In many embodiments, the data signal may be communicated via the light source at amplitude modulating frequencies such that the resulting flicker is not perceivable to the human eye.