Ultrasonic Indoor Positioning via Signal Reliability Filtering
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Solution Overview
Problem
Accurately determining the position of a user or mobile device within an indoor setting is challenging due to limitations in consumer devices' communication and sensing capabilities, especially when GPS is unavailable, as existing technologies struggle with interference and accuracy in enclosed spaces.
Innovation Solution
A sound-based positioning system using ultrasonic signals from multiple sound signal sources, where receiving devices capture and process sound signals to determine their initial position through multilateration, and update their position as reliability varies, accounting for dynamic interference and movement by filtering out unreliable signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS technologies are used for positioning, then location information can be obtained outdoors, but GPS signals are impeded by surrounding structures in enclosed buildings making positioning unavailable
Solution Approach 1:
The patent replaces GPS satellite-based electromagnetic signal positioning with an acoustic-based positioning system using ultrasonic sound waves. The system uses acoustic signal generators emitting ultrasonic signals and microphones to detect these signals, calculating position based on time of arrival differences. This substitution allows positioning to function indoors where GPS signals are blocked by building structures.
2Ease of manufacture
If consumer devices are used for acoustic positioning, then no hardware modifications are needed, but limitations in communication capabilities, sensing capabilities, internal clock accuracy, and power constrain positioning accuracy
Solution Approach 1:
The patent employs spread spectrum modulation techniques and ultrasonic frequency signals to enhance positioning accuracy using consumer device components. By modulating acoustic signals with pseudorandom codes and using ultrasonic frequencies above human hearing range, the system achieves higher precision in time of arrival measurements despite limitations in consumer device microphones and processors.
Solution Approach 2:
The patent introduces acoustic signal generators and uses spread spectrum modulation as intermediaries between the positioning system and consumer devices. These intermediaries translate positioning requirements into forms that consumer device microphones and processors can handle effectively, bridging the gap between system requirements and device capabilities.
3Reliability
If acoustic signals are used for positioning, then indoor positioning is enabled, but environmental interference, multipathing, and movement cause variability in signal reliability
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors signal quality metrics such as signal-to-noise ratio, correlation peak strength, and time of arrival consistency. Based on this feedback, the system dynamically adjusts signal processing parameters, selects the most reliable acoustic signals for positioning calculations, and compensates for environmental interference and multipathing effects.
Solution Approach 2:
The patent converts the challenge of multipathing (signals arriving via multiple paths) into a benefit by using spread spectrum correlation techniques that can distinguish direct signals from reflected signals. The system uses the temporal and spatial characteristics of multipath signals to enhance positioning accuracy rather than treating them purely as interference.
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 accurate, real-time location determination within indoor environments by utilizing consumer-grade mobile devices with improved accuracy and reliability, even in the presence of changing obstructions and interference, by employing differential and non-differential time of arrival measurements.
Implementation Method 1
sound signal sources (e.g., speakers) distributed throughout a given area. The sound signals emitted by the sound signal sources are received by one or more receiving devices (e.g., mobile devices having microphones capable of accurately capturing ultrasonic sound signals)
Implementation Method 2
use the received sound signals to compute a location within the given area. A receiving device can determine its initial position from the received sound signals using multilateration, a process of determining a position of a receiving device based on accurately computing the time difference of arrival (TDOA) of signals transmitted from multiple sound signal sources
Data Source
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AI summary
A receiving device captures sounds signals (e.g., ultrasonic) from multiple sound signal sources, selects the sound signals satisfying a reliability condition for use in determining an initial position of the receiving device relative to the corresponding sound signal sources, determines the initial position of the receiving device using multilateration of the selected sound signals, and updates the current position of the receiving device as the reliability of individual sound signals varies in the presence of dynamically changing environmental interference, multipathing, and movement between the receiving device and the sound signal sources.