Modulated LED Beacon for Indoor Positioning Accuracy
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Solution Overview
Problem
Existing 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 digital pulse recognition signals transmitted by light sources, such as LEDs, to determine the position of mobile devices by broadcasting unique identification codes through visible light, allowing for precise location determination using photogrammetric techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used for positioning, then outdoor location accuracy is achieved, but indoor positioning accuracy deteriorates due to signal blockage and multipath propagation
Solution Approach 1:
The patent replaces radio-based GPS positioning with an optical-based positioning system using visible light from LED sources. The system captures images of LED lights with a camera, extracts modulation frequencies through spectral analysis, and determines position based on optical signal characteristics rather than radio wave propagation, thereby achieving reliable indoor positioning where GPS fails
Solution Approach 2:
The patent modulates LED light sources at specific frequencies (e.g., 300 Hz, 600 Hz, 900 Hz) to encode identification information. By changing the modulation frequency parameter of the light sources, the system enables receivers to distinguish between different LED lights and determine precise position through frequency-based identification rather than relying on blocked or reflected radio signals
2Ease of operation
If radio waves are used for indoor positioning, then wireless communication is achieved, but positioning accuracy deteriorates due to unpredictable propagation in complex indoor environments
Solution Approach 1:
The patent substitutes radio wave-based wireless positioning with visible light-based optical positioning. The system uses camera-equipped receivers to capture images of modulated LED lights and determines position through optical signal processing, eliminating the problems of radio wave multipath propagation and interference while maintaining wireless operation
Solution Approach 2:
The patent employs periodic modulation of LED light sources at distinct frequencies to encode identification information. Each LED light modulates its output periodically at a unique frequency (e.g., 300 Hz, 600 Hz, 900 Hz), allowing the receiver to identify and locate specific lights through spectral analysis of the periodic optical signals, thereby achieving accurate positioning without radio wave propagation issues
3Measurement precision
If LED modulation frequency is increased to improve data transmission rate, then positioning precision is improved, but human eye detectability increases causing discomfort
Solution Approach 1:
The patent carefully selects LED modulation frequencies within the range of 300 Hz to 900 Hz, which is above the typical human flicker fusion threshold. By changing the frequency parameter to this specific range, the system achieves sufficient precision for position determination through spectral analysis while keeping the modulation imperceptible to the human eye, thus avoiding visual discomfort
Solution Approach 2:
The patent uses the camera sensor to capture and analyze the modulated light signal, creating a digital copy of the optical signal for processing. The spectral analysis is performed on the captured image data rather than directly on the light, allowing precise frequency detection without exposing the human eye to high-frequency modulation, thereby maintaining both precision and comfort
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
The system provides accurate three-dimensional positioning with high precision, enabling effective indoor navigation and content delivery by leveraging the directional nature of optical signals and the ability of LEDs to transmit data undetectable to the human eye but perceivable by image sensors.
Implementation Method 1
a first light source of a plurality of light sources, each light source having an associated identification code and modulated to transmit at a frequency
Implementation Method 2
modulated to transmit at a frequency corresponding to its identification code
Implementation Method 3
a second device including a camera that captures an image of the first light source
Implementation Method 4
performing a spectral analysis on the captured image to determine a frequency of the light source
Implementation Method 5
allowing for precise location determination using photogrammetric techniques
Data Source
AI summary
In one aspect, the present disclosure relates to a method for broadcasting a modulated digital pulse recognition signal from a light source. In some embodiments, the method includes selecting one or more digital pulse recognition tones to broadcast, determining a desired brightness level for the light source, generating a digital pulse recognition signal having a duty cycle based on the desired brightness level and a frequency based on the one or more digital pulse recognition tones, and driving the output of the light source with the digital pulse recognition signal. In some embodiments, selecting one or more digital pulse recognition tones to broadcast includes generating a single periodic tone for differentiating the light source from a nearby light source. In some embodiments, selecting one or more digital pulse recognition tones to broadcast includes generating a sequence of periodic tones.