Indoor Position Tracking Using TDOA Synchronization Pulses
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Solution Overview
Problem
Conventional GPS systems are ineffective in providing accurate real-time position monitoring in GPS-denied areas, such as indoors or enclosed spaces, where a line of sight to satellites is obstructed, and existing alternatives fail to achieve DGPS-level resolution over large areas.
Innovation Solution
A system comprising mobile nodes, reference nodes, and a command node that uses a simple clock counting scheme to measure Time Difference of Arrival (TDOA) of synchronization pulses to achieve sub-meter resolution in a 1 km target area, allowing for real-time position tracking without requiring an unobstructed line of sight to GPS satellites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GPS systems are used for position monitoring, then outdoor positioning accuracy is achieved, but the system becomes ineffective in GPS-denied areas where line of sight to satellites is obstructed
Solution Approach 1:
The patent introduces reference nodes as intermediary devices that receive GPS signals and redistribute them within the indoor environment. These reference nodes act as mediators between the external GPS system and the indoor mobile nodes, enabling positioning without direct satellite visibility. The reference nodes transmit synchronization pulses that allow mobile nodes to calculate their positions relative to the reference framework, thus solving the line-of-sight limitation.
2Adaptability or versatility
If existing indoor positioning alternatives (WiFi, ultrasound, cellular) are used, then operation in GPS-denied areas is achieved, but positioning accuracy fails to reach DGPS-level resolution
Solution Approach 1:
The patent replaces conventional indoor positioning methods (WiFi, ultrasound, cellular) with a radio frequency-based TDOA system that uses synchronization pulses transmitted at known times. By measuring the time difference of arrival of these pulses and knowing the precise locations of reference nodes, the system achieves DGPS-level accuracy. This substitution of the positioning mechanism enables both indoor operation and high precision simultaneously.
3Measurement precision
If a system provides real-time position tracking with high accuracy, then measurement precision is improved, but device complexity increases due to the need for precise timing mechanisms
Solution Approach 1:
The patent segments the timing function by separating the reference nodes (which maintain precise GPS-based timing) from the mobile nodes (which only measure arrival times). The reference nodes handle the complex synchronization and positioning calculations, while mobile nodes perform simple TDOA measurements. This segmentation reduces the complexity burden on mobile devices while maintaining high accuracy.
Solution Approach 2:
The system uses the mobile nodes' own local clocks to measure the arrival times of synchronization pulses. Each mobile node independently measures the time difference between pulses from different reference nodes using its local timing mechanism, eliminating the need for complex external synchronization equipment. The nodes self-determine their positions based on these local measurements and the known reference node locations.
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 indoor position tracking with sub-meter resolution, scalable to monitor up to 50 mobile nodes, and integrates with GIS maps for real-time display, operating reliably through walls and in RF multipath environments with a fast update rate.
Implementation Method 1
the mobile nodes receive the sync pulses from the reference nodes and records the exact time it receives the pulses from all three reference nodes, with the difference between the received times being the difference in radio frequency ('RF') propagation time
Data Source
AI summary
A method and system for increased position tracking resolution in a localized environment for use in GPS-denied areas such as within buildings or enclosed structures, comprising: multiple reference nodes each transmitting a synchronization pulse to a multitude of body-worn or device-mounted receiving units; a high speed clock circuit in each receiver capable of measuring the Time Difference of Arrival of said sync pulses to the resolution needed for precise positioning; a central processing computer used to calculate actual position of the receiving units relative to some fixed reference point; and a display system to monitor the position of the receiving units in real time as they move around within the target area overlaid onto available GIS data or building CAD drawings.