Dynamic Path Loss Exponent Calibration for Indoor Positioning
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Solution Overview
Problem
Current wireless communication technologies face challenges in accurately determining the distance and position of a wireless mobile device within a building, especially when it is not wirelessly associated with another device, as time-of-flight measurements are not possible in such cases, limiting indoor navigation and localization capabilities.
Innovation Solution
A wireless channel calibration apparatus dynamically calibrates the path loss exponent based on channel characteristics, including received signal strength and path length measurements, allowing for the estimation of channel parameters and triangulation of device positions even without direct wireless association, using techniques like TOF measurements and geometric relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time-of-flight measurements are used to determine distance, then distance measurement precision is improved, but wireless association is required which limits applicability
Solution Approach 1:
The patent uses received signal strength as an intermediary parameter to estimate distance when direct TOF measurement is not available. By calibrating the relationship between signal strength and distance through the path loss exponent, the system can determine distances between devices that are not wirelessly associated, thus extending applicability while maintaining reasonable measurement precision
Solution Approach 2:
The system dynamically adjusts the path loss exponent parameter based on environmental conditions and calibration data. This parameter change allows the distance estimation model to adapt to different scenarios (line-of-sight vs. non-line-of-sight, indoor vs. outdoor), improving both precision and versatility across various operating conditions
2Measurement precision
If GPS is used for position determination, then outdoor positioning accuracy is improved, but indoor positioning capability is lost
Solution Approach 1:
The patent replaces GPS satellite-based positioning with a wireless signal-based positioning system. By using WiFi signal strength measurements and triangulation methods, the system achieves indoor positioning capability while maintaining competitive accuracy, substituting the GPS mechanical/satellite system with an electromagnetic field-based system that works indoors
Solution Approach 2:
The system transitions from three-dimensional outdoor GPS coordinates to a hybrid positioning approach that combines signal strength measurements (adding a signal dimension) with spatial triangulation. This allows positioning in indoor environments where GPS signals are unavailable, expanding versatility while maintaining accuracy through multi-dimensional data fusion
3Measurement precision
If dynamic path loss exponent calibration is performed, then channel parameter estimation accuracy is improved, but measurement and calculation complexity increases
Solution Approach 1:
The system performs preliminary calibration measurements during initial setup or known conditions to establish baseline path loss exponent values. These pre-calibrated parameters are then used in normal operation, reducing the frequency of complex measurements while maintaining accuracy. The calibration data is stored and reused, decreasing ongoing measurement complexity
Solution Approach 2:
The system automatically performs calibration and parameter adjustment without requiring manual intervention. Through self-calibration routines using available signal measurements and known device positions, the system maintains accurate channel parameters while reducing operational complexity. The automatic nature of the process eliminates manual measurement burden
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 navigation and localization by determining device positions and path lengths, enhancing wireless communication systems' ability to function without line-of-sight and in environments with electromagnetic interference, such as buildings.
Implementation Method 1
N-determining factors include the length D1 of a path between the two wireless stations as determined by TOF measurements
Implementation Method 2
the terms 'channel,' 'communication channel,' and 'wireless channel' shall mean a set of factors influencing the propagation of selected electromagnetic signals
Data Source
AI summary
Apparatus, systems, and methods disclosed herein operate to calibrate path loss parameters corresponding to a communication channel between wireless stations, including a path loss exponent. A time-of-flight (TOF) associated with packet transmissions traversing a path between a first wireless station and a second wireless station is measured. A path length D1 corresponding to the path is calculated from the TOF measurements. One or more received signal strength (RSS) measurements corresponding to the packet transmissions are then made at the first wireless station. The path loss exponent associated with the path is calculated from D1 and the RSS measurements. Some embodiments may also measure RSS values associated with transmissions from a third wireless station. The latter measurements may be used in conjunction with the previously-determined path loss exponent to derive an unknown transmission path length between the first and third wireless stations. The latter path length may be used together with other known station geometry to determine the coordinate position of the first wireless station.