Indoor Location Path Segment Matching Using WiFi Signals
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Solution Overview
Problem
Existing methods for estimating the location of wireless mobile devices indoors are inaccurate due to weak GPS signals and other sources of error such as low sampling rates and high location latency, making it difficult to provide reliable location-based services in indoor structures.
Innovation Solution
The system uses path segment matching techniques, including Hidden Markov Models, to estimate the location of mobile devices by modeling transitions between path segments within a structure, utilizing emission and transition probabilities, and aligning device locations with the most likely path segments based on distance, time, and angle constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS signals are used for indoor location estimation, then location-based services can be provided, but the accuracy deteriorates due to weak GPS signals indoors
Solution Approach 1:
The patent introduces WiFi access points as intermediary objects to enable location estimation indoors. Instead of relying directly on GPS signals which are weak indoors, the system uses WiFi signal strengths from multiple access points as intermediate measurements to infer location, thereby maintaining service availability while improving accuracy in indoor environments
Solution Approach 2:
The patent replaces the GPS-based location estimation mechanism with a WiFi-based mechanism for indoor environments. By substituting the mechanical/GPS signal reception system with a WiFi signal reception and processing system, the patent achieves accurate indoor location estimation where GPS fails
2Ease of manufacture
If traditional location estimation methods are used, then the system is simple to implement, but the accuracy deteriorates due to low sampling rates and high location latency
Solution Approach 1:
The patent implements feedback mechanisms by continuously monitoring WiFi signal strengths from multiple access points and using this feedback to update and refine location estimates. The system processes a series of location estimates over time, using the pattern of signal strength changes to improve accuracy and reduce latency compared to single-point estimation methods
Solution Approach 2:
The patent performs preliminary actions by pre-establishing a database of access point locations and signal characteristics, and pre-computing probability distributions for location estimation. This preliminary preparation enables faster, more accurate real-time location estimation without complex processing during actual location queries
Data Source
AI summary
A method including obtaining location estimates of a wireless mobile device inside a structure based on wireless signals transmitted by the wireless mobile device and received at a plurality of wireless access points, wherein the inside of the structure is represented by a plurality of path segments; modeling a transition from a first estimated location of the wireless mobile device to a second estimated location of the wireless mobile device by minimizing a ratio of an angle to a length between the first estimated location and the second estimated location; selecting, based on the modeling a particular path segment of the plurality of path segments; and aligning the second estimated location of the mobile device to the particular path segment. An apparatus and a computer-readable storage media implementing the method are also disclosed.