Indoor RF Positioning Using Anchor Stations and TDOA
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Solution Overview
Problem
Existing GPS systems are unsuitable for indoor and dense industrial environments due to signal attenuation and multipath propagation, leading to inaccurate location determination, and require a larger number of anchor stations for unobstructed line of sight.
Innovation Solution
A positioning system using a network of anchor stations and mobile stations based on WirelessHART® and Ultra-Wide Band communication, employing time difference of arrival measurements and TDMA to determine location with reduced crosstalk and multipath errors, utilizing a central station for network optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS systems are used for indoor positioning, then global positioning is achieved, but signal attenuation and multipath propagation cause inaccurate location determination
Solution Approach 1:
The patent replaces GPS satellite-based positioning with a wireless sensor network system that uses RF signals transmitted through the building structure. Instead of relying on satellite signals that suffer from attenuation and multipath effects, the system employs a distributed network of anchor stations and mobile stations that communicate via wireless links, eliminating the harmful effects of signal attenuation and multipath propagation while achieving accurate indoor positioning
Solution Approach 2:
The patent introduces wireless sensor nodes as intermediaries between the positioning system and the environment. These nodes act as mediators that transmit RF signals through the building structure, enabling positioning without direct line-of-sight to satellites. The intermediary nodes process and relay positioning information, allowing accurate location determination despite the presence of obstacles and reflective surfaces
2Measurement precision
If more anchor stations are deployed to ensure unobstructed line of sight, then positioning accuracy is improved, but system complexity and installation cost increase
Solution Approach 1:
The patent applies partial action by requiring only a limited number of anchor stations (at least three) to achieve accurate positioning through trilateration. Instead of deploying a comprehensive network of anchor stations throughout the entire building, the system uses a minimal set of strategically placed anchors that provide sufficient geometric coverage. This partial deployment approach reduces system complexity and installation costs while maintaining positioning accuracy
Solution Approach 2:
The patent implements dynamic positioning where mobile stations can move freely through the environment and maintain positioning capability. The system dynamically adjusts the positioning calculation based on the current locations of mobile stations relative to anchor stations. This dynamic approach allows the system to maintain accuracy without requiring a fixed, extensive network of anchor stations, as the positioning algorithm adapts to the mobile station's position and the available anchor station geometry
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
Achieves accurate and robust location tracking in indoor and dense environments with reduced installation costs and power consumption, enabling precise positioning of multiple objects or personnel with minimal overlap and interference.
Implementation Method 1
Each anchor station transmits a RF signal to the mobile station. The mobile station measures a time difference of arrival of the RF signals from the multiple anchor stations
Implementation Method 2
TDMA is a known standard for sharing a frequency channel on a network, by dividing the signal into multiple time slots. Each station, such as anchor stations 302, may share the frequency being used for pulses by being assigned a specific time slot for transmissions
Data Source
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Figure 4
AI summary
A positioning system (300), includes a plurality of anchor stations (302) each configured to transmit a radio frequency signal (320). A mobile station (304) includes a radio frequency transceiver configured to transmit and receive a radio frequency signal from at least one of the plurality of anchor stations (302). A processing unit (408, 506) is configured to determine position information of the mobile station (304) based upon the transmitted and received radio frequency signal. Another positioning system uses a number of beacons (604) ranging a number of mobile tags (606) with ultra-wide band ranging (612), and communicating wirelessly with an application server (602).