Light-Based Positioning Using Modulated LED Signals
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Solution Overview
Problem
Satellite-based positioning systems are unreliable in non-line of sight (NLOS) environments, necessitating a precise positioning method that can function independently of these systems.
Innovation Solution
A light-based positioning system using LED lighting that modulates pseudorandom sequences to enable precise time-of-flight measurements, allowing for three-dimensional location determination through triangulation with multiple light sources, even in noisy conditions, without requiring radio frequencies or costly positioning techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If satellite-based positioning systems are used, then global location measurement is achieved, but the system becomes unavailable or unreliable in non-line of sight (NLOS) environments
Solution Approach 1:
The patent replaces satellite-based radio frequency positioning with a light-based positioning system using LEDs and photodetectors. This substitution enables positioning in NLOS environments by using visible light instead of radio waves, achieving both reliability and environmental adaptability through a fundamentally different physical mechanism.
Solution Approach 2:
The system changes the fundamental parameter of signal type from radio frequency to optical frequency. By modulating LED light sources with pseudorandom sequences and detecting them with photodetectors, the system achieves reliable positioning in indoor and NLOS environments where satellite signals fail.
2Reliability
If light-based positioning is implemented, then positioning in NLOS environments is enabled, but signal detection becomes difficult in noisy ambient lighting conditions
Solution Approach 1:
The patent divides the positioning signal into multiple segments: unique pseudorandom sequences are assigned to different LED light sources, allowing the receiver to distinguish between multiple light sources and separate the modulated positioning signal from ambient lighting noise through code correlation.
Solution Approach 2:
The system uses periodic modulation of LED light sources with pseudorandom sequences at specific frequencies. This periodic action creates a detectable signal pattern that stands out from random ambient lighting variations, enabling reliable signal detection through synchronous detection techniques.
3Measurement precision
If pseudorandom sequences are modulated on light sources, then precise time-of-flight measurements are enabled, but the system complexity increases
Solution Approach 1:
The patent uses pseudorandom sequences as code copies that can be generated and correlated at both transmitter and receiver ends. This copying approach enables precise time-of-flight measurements through correlation peak detection without requiring complex hardware, as the same sequences are replicated across multiple LED sources and the receiver.
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
Enables rapid and precise location control in indoor environments, suitable for applications like factory automation, retail navigation, and autonomous vehicle navigation, without the limitations of satellite systems or RF spectrum regulations.
Implementation Method 1
a photodetector to convert received light to an electrical signal
Data Source
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AI summary
Methods and apparatus to determine a position using light sources are disclosed. An example method includes processing an output of a photodetector based on anticipated codes to identify multiple light sources from which the photodetector receives light at a first position, determining locations of the identified light sources; and determining a location of the first position based on the locations of the identified light sources.