Fourier Transform Demodulation for Indoor Light Positioning
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Solution Overview
Problem
Current indoor positioning systems face challenges in accuracy due to the limitations of GPS in indoor environments and the unpredictability of radio wave propagation in complex indoor settings, necessitating a more reliable and accurate method for locating mobile devices within buildings.
Innovation Solution
A light-based positioning system that uses modulated light signals from LED sources, where the modulation frequency is undetectable to the human eye but can be received by cameras, allowing for precise determination of device position through Digital Pulse Recognition (DPR) demodulation techniques, which exploit the rolling shutter mechanism of CMOS image sensors to recover digital data from optically encoded signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used for indoor positioning, then outdoor location accuracy is maintained, but indoor positioning accuracy deteriorates due to signal blockage
Solution Approach 1:
The patent introduces light sources (LEDs) as intermediary objects that emit modulated light signals serving as positioning beacons. These light sources act as mediators between the positioning system and mobile devices, enabling accurate indoor localization by replacing GPS with optical signals that can penetrate indoor environments effectively
Solution Approach 2:
The patent replaces the radio wave-based GPS system with a light-based positioning system. By substituting electromagnetic radio waves with optical light signals from LED sources, the system achieves reliable indoor positioning where GPS fails due to signal blockage by buildings
2Adaptability or versatility
If radio wave propagation is used for indoor positioning, then wireless communication is enabled, but positioning accuracy deteriorates due to unpredictable propagation in complex indoor settings
Solution Approach 1:
The patent changes the fundamental parameter of signal type from radio waves to light waves. By operating in the optical domain with modulated LED light sources, the system achieves predictable signal propagation and precise positioning accuracy while maintaining wireless communication capability through optical channels
3Productivity
If modulation frequency is increased for higher data rates, then communication speed improves, but detection difficulty increases beyond human eye perception
Solution Approach 1:
The patent introduces camera-based image sensors as intermediary detection devices that can capture and analyze high-frequency modulated light signals. These sensors act as mediators between the high-speed modulated light source and the processing system, enabling detection of frequencies far beyond human visual capabilities
Solution Approach 2:
The patent replaces human eye detection with electronic image sensor detection. By substituting biological visual perception with electronic sensor arrays and digital signal processing, the system can detect and measure high-frequency modulations that encode data at rates impossible for human observation
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 provides high accuracy and reliability in indoor positioning, enabling precise location determination and content delivery to mobile devices, with the potential for higher data rates and reduced power consumption in communication-enabled lighting devices.
Implementation Method 1
recording the modulated light signal using a rolling shutter image sensor to create a raw image having alternating spaced apart stripes
Implementation Method 2
recording the modulated light signal using a rolling shutter image sensor
Implementation Method 3
taking a Fourier transform of an image representative of the isolated image to calculate a Fourier transformed signal
Data Source
AI summary
In one aspect, the present disclosure relates to a method for demodulating a modulated light signal in a light based positioning system. In some embodiments, the method includes receiving a modulated light signal at a device, the modulated light signal transmitting an arbitrary identifier of a light source, recording the modulated light signal using a rolling shutter image sensor to create a raw image having alternating spaced apart stripes, subtracting background information from the raw image to create an isolated image, taking a Fourier transform of an image representative of the isolated image to calculate a Fourier transformed signal, and determining the arbitrary identifier of the light source based on the Fourier transformed signal.