Indoor Positioning System Using Ultra-Wideband Time of Flight
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Solution Overview
Problem
Conventional GPS systems are ineffective for indoor and dense industrial environments due to signal attenuation and multipath propagation, requiring a specialized positioning system that can accurately determine location without relying on GPS and minimize errors caused by reflections and diffraction.
Innovation Solution
A positioning system utilizing a network of anchor stations and mobile stations with radio frequency transceivers, employing time of flight measurements and trilateration, along with battery-powered beacons for wireless communication, to determine the position of mobile units using ultra-wide band communication and time slot management to reduce crosstalk and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS systems are used for positioning, then outdoor location accuracy is improved, but indoor positioning capability deteriorates due to signal attenuation and multipath propagation
Solution Approach 1:
The patent introduces anchor stations as intermediary devices deployed throughout the indoor environment. These anchor stations transmit RF signals that serve as mediators between the positioning system and the mobile station, enabling location determination without requiring direct GPS satellite signals. The anchor stations act as local reference points that compensate for the inability of GPS to penetrate indoor structures.
Solution Approach 2:
The patent replaces the GPS-based positioning mechanism with an RF signal-based time of flight measurement system. Instead of relying on satellite signals that cannot penetrate buildings, the system uses radio frequency signals transmitted by anchor stations and received by mobile stations to calculate distances through time measurement, thereby substituting the failing GPS mechanism with a functional indoor alternative.
2Ease of operation
If time of flight measurements are used for positioning, then location determination is enabled, but positioning error increases due to clock synchronization inaccuracies
Solution Approach 1:
The patent implements feedback mechanisms where the mobile station receives not only the timestamp of the anchor station's signal transmission but also the timestamp of the signal reception. This feedback information allows the system to calculate the round-trip time and compensate for clock synchronization errors between different devices, thereby improving positioning accuracy despite the presence of timing inaccuracies.
Solution Approach 2:
The system performs preliminary actions by having anchor stations transmit signals with embedded timestamps before the actual positioning measurement. This preliminary timestamping allows the mobile station to later compare transmission and reception times, enabling error compensation in the time of flight calculation and improving overall positioning precision.
3Reliability
If multiple anchor stations are deployed to ensure unobstructed line of sight, then positioning reliability is improved, but system complexity increases
Solution Approach 1:
The patent applies partial action by requiring only a minimum number of anchor stations (typically three or more) to achieve reliable positioning through trilateration. Rather than deploying every possible anchor station throughout the environment, the system uses the minimum necessary number to ensure unobstructed line of sight and reliable location determination, thereby reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The system dynamically determines which anchor stations are visible and accessible from the mobile station's current location. Rather than requiring a fixed, comprehensive network of anchor stations, the system adapts its operation based on the mobile station's position, using only the necessary anchor stations that provide unobstructed line of sight at any given moment, thus reducing complexity while maintaining reliability.
4Adaptability or versatility
If RF signals are used for positioning, then indoor location tracking is enabled, but signal attenuation and multipath propagation cause positioning errors
Solution Approach 1:
The patent converts the harmful effect of signal reflections into a beneficial feature by using the received signal strength and timing information from multiple reflected paths to improve positioning accuracy. Instead of simply rejecting multipath signals as errors, the system utilizes the temporal and amplitude characteristics of these reflected signals to distinguish between direct and reflected paths, thereby converting what would normally be harmful into useful positioning data.
Solution Approach 2:
The system changes the parameters used for signal evaluation by focusing on time-based measurements (time of flight, signal arrival time) rather than purely amplitude-based measurements. By using temporal parameters and comparing signal arrival times across multiple anchor stations, the system can distinguish between direct and reflected paths more effectively, reducing the impact of signal attenuation and multipath propagation on positioning accuracy.
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 achieves accurate location determination in harsh environments by minimizing multipath errors and ensuring unobstructed line of sight to multiple anchor points, enabling reliable tracking of objects or people within indoor and industrial areas with reduced installation costs and improved robustness.
Implementation Method 1
a plurality of anchor stations each configured to transmit and receive a radio frequency signal. A mobile station includes a radio frequency transceiver configured to transmit and receive a radio frequency signal from at least one of the plurality of anchor stations
Implementation Method 2
Time of flight (ToF) is the amount of time a signal takes to propagate from transmitter to receiver. Because the signal propagation rate is constant and known, the travel time of a signal can be used directly to calculate distance
Implementation Method 3
A positioning system utilizing a network of anchor stations and mobile stations with radio frequency transceivers, employing time of flight measurements and trilateration, along with battery-powered beacons for wireless communication
Data Source
AI summary
A positioning system, includes a plurality of anchor stations each configured to transmit a radio frequency signal. A mobile station includes a radio frequency transceiver configured to transmit and receive a radio frequency signal from at least one of the plurality of anchor stations. A processing unit is configured to determine position information of the mobile unit based upon the transmitted and received radio frequency signal. Another positioning system uses a number of beacons ranging a number of mobile tags with ultra-wide band ranging, and communicating wirelessly with an application server.