Wireless Client Position Estimating System Using Signal Attenuation
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Solution Overview
Problem
Existing methods for determining the position of a mobile wireless client device in a wireless LAN environment are cumbersome, requiring extensive data collection and software installation, and are inaccurate due to variations in device specifications and signal propagation complexities.
Innovation Solution
A system that calculates the error between expected and received signal strength at multiple locations using an attenuation model, allowing for the determination of the device's position without the need for extensive data collection or software on the client device, by employing access points to measure signal strength and normalize vendor variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If RSSI-based positioning methods are used, then positioning functionality can be implemented using existing IEEE 802.11 hardware, but the methods require extensive data collection and field surveying to build accurate radio maps or calibrate propagation models
Solution Approach 1:
The system performs preliminary actions by pre-calculating and storing propagation loss values for various distances between access points and client devices during system initialization. These pre-computed propagation loss values are stored in a database, eliminating the need for time-consuming field surveying and data collection during actual positioning operations.
Solution Approach 2:
The patent creates a simplified copy of the complex real-world signal propagation environment by using pre-measured propagation loss data from controlled conditions. This copied data is stored in a database and used to infer client device positions without requiring repeated field measurements during actual positioning tasks.
2Measurement precision
If radio map algorithms are used to determine client position, then positioning can be achieved using RSSI measurements, but the radio map becomes invalid when access points move or the environment changes, requiring re-collection of data
Solution Approach 1:
The system dynamically adapts to environmental changes by continuously monitoring signal strength measurements from client devices and updating the propagation loss database accordingly. When access points move or the environment changes, the system collects new measurement data and updates the pre-computed propagation loss values, maintaining positioning accuracy without requiring complete re-collection of radio map data.
3Loss of time
If signal propagation modeling is used to compute expected signal strength, then positioning can be performed without extensive data collection, but the modeling is overly complex and unlikely to work in practice due to the difficulty of accurately modeling signal propagation inside structures
Solution Approach 1:
Instead of using complex, expensive-to-implement signal propagation models that require detailed knowledge of building structures and materials, the patent uses simple, pre-computed propagation loss values based on distance measurements. These simplified propagation loss values are stored in a database and applied directly to positioning calculations, providing practical accuracy without the complexity of full signal propagation modeling.
4Quantity of substance
If RSSI measurements are taken by mobile wireless client devices, then positioning data can be collected, but the readings vary significantly due to different technical specifications among various device vendors
Solution Approach 1:
The patent introduces an intermediary normalization process that converts RSSI measurements from different vendor devices into a common reference frame. The system measures the actual signal strength between access points and client devices, compares these measurements against the pre-stored propagation loss values, and uses the difference to calculate positions. This intermediary comparison process normalizes readings across different vendors by removing the effect of device-specific transmission power variations.
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
This approach provides a more accurate and efficient method for determining the position of wireless client devices, reducing the complexity of data collection and eliminating the need for specialized hardware or software on the client device, while normalizing signal variations across different vendors.
Implementation Method 1
signal propagation is modeled by taking into consideration obstructions in the signal propagation path, such as walls, furniture, and other objects in the environment
Implementation Method 2
building a model of the communications environment comprising attenuation factors that approximate an attenuation effect on propagation of communications signals
Data Source
AI summary
The present invention comprises a system and method for determining an estimated position of a wireless mobile client device operating in a communications environment covered by a wireless local area network. The received signal strength of the wireless mobile client device is measured by one or more access points serving devices in the communications environment. In a preferred embodiment, the error between the received signal strength measured by the access points and the expected received signal strength at a plurality of locations in the communications environment is calculated. The location of the device is determined from the error.