Probabilistic Location Detection Using Wireless Signal Weighting
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Solution Overview
Problem
Existing location detection methods in environments where GPS is unavailable or unreliable, such as indoors or in urban areas, face challenges due to fluctuating wireless signal strengths and obstacles, leading to inaccurate location determination, especially when using consumer devices like mobile phones.
Innovation Solution
A method that combines prior location estimates with signal-based values and transition probabilities using a matrix-based approach, incorporating doubly stochastic transition matrices to account for all possible transitions and complex signal environments, and adjusts for device-specific signal processing differences through normalization and transformation of signal strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal strength-based location detection is used in environments with obstacles and walls, then location detection can be performed in GPS-denied areas, but accuracy deteriorates due to signal fluctuation and attenuation
Solution Approach 1:
The patent introduces a probabilistic model as an intermediary layer between signal measurements and location determination. Instead of directly mapping signal strength to location, the system uses probability distributions to represent the relationship, accounting for signal fluctuations caused by obstacles and environmental factors. This mediator handles the uncertainty and improves accuracy despite signal attenuation.
Solution Approach 2:
The system transforms the deterministic signal strength-to-location relationship into a probabilistic parameter model. By changing from fixed signal strength thresholds to probability distributions across multiple sample points, the system can better handle signal variations caused by walls and obstacles, improving location accuracy in challenging environments.
2Measurement precision
If multiple WAPs are deployed to improve location accuracy through signal triangulation, then location precision can be enhanced, but device complexity and system cost increase
Solution Approach 1:
The system uses existing wireless access points that are already deployed for their primary networking function. Instead of requiring dedicated tracking infrastructure, the location detection leverages the existing WAPs' broadcast signals, making the system self-sufficient and avoiding additional hardware complexity while maintaining location accuracy.
Solution Approach 2:
The patent makes the existing wireless access points serve dual purposes: their original networking function and location detection. By using the same WAPs for both data communication and location tracking, the system avoids deploying separate tracking infrastructure, reducing overall system complexity while achieving accurate location determination.
3Speed
If signal strength measurements are taken frequently to track movement, then location tracking responsiveness improves, but energy consumption increases
Solution Approach 1:
The system implements periodic location updates rather than continuous tracking. By taking measurements at regular intervals and using probabilistic models to interpolate between measurements, the system maintains responsive location tracking while reducing the frequency of actual signal measurements, thereby lowering energy consumption compared to continuous monitoring.
Data Source
AI summary
A system and method for detecting the location of a mobile device within an area, uses a plurality of wireless signals sent to or received by the device to derive a first estimate of the position of the device. This position estimate is then adjusted using a probabilistic model of the area, where the area is divided into zones or regions, and where each region is assigned a weighting according to the probability of the device being located in that region taking account of the prior position of the device. By using the weightings to adjust the position estimate, false or ambiguous position estimates are discounted and the true position of the device is more reliably detected. The method also includes techniques to take account of different wireless characteristics of different devices when each is supplied with the same model.