Wireless Signal Strength Movement Detection Using Adaptive Thresholds

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Solution Overview

Problem

Existing technologies face challenges in accurately detecting movement of computing devices between general locations, especially in indoor environments, due to limitations in processing requirements, location granularity, and reliance on external devices like GPS.

Innovation Solution

A computerized method and system that utilizes signal strength data from wireless access points to detect movement of a computing device. The system determines a signal strength range during a learning time period and provides notifications during a detection time period if the device moves outside this range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If GPS technology is used to detect device movement, then location accuracy is improved, but processing requirements increase and reliability decreases indoors

Engineering Contradiction:
Improvelocation accuracyVSAvoidprocessing requirements
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces GPS (mechanical/satellite-based) with wireless signal strength measurement (electromagnetic field-based). The system uses access point signal strength data to detect device movement, eliminating the need for GPS hardware and complex processing while maintaining indoor reliability through wireless infrastructure that is already present in the environment.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces wireless signal strength as an intermediary measurement to detect movement. Instead of directly measuring location with GPS, the system uses signal strength changes from access points as a proxy indicator that correlates with device position, simplifying the system while maintaining detection capability.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If GPS technology is used to detect device movement, then location accuracy is improved, but reliability worsens indoors

Engineering Contradiction:
Improvelocation accuracyVSAvoidindoor reliability
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent replaces GPS with wireless signal strength measurement, which is inherently more reliable indoors since it uses the existing wireless infrastructure (access points) that provides coverage throughout indoor spaces. The signal strength data is continuously available and does not require external satellite signals or additional hardware.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If 802.11mc location-finding is used, then location capability is improved, but processing requirements increase

Engineering Contradiction:
Improvelocation capabilityVSAvoidprocessing requirements
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for movement detection from the wireless signal data - specifically signal strength values - rather than implementing the full 802.11mc location-finding system. This selective extraction approach maintains location capability while significantly reducing processing requirements by ignoring unnecessary data and using simple threshold comparisons.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies partial action by using simplified signal strength threshold comparisons instead of comprehensive location-finding algorithms. The system uses basic processing (comparing signal strength to thresholds) rather than complex multivariate analysis, achieving sufficient location capability with minimal processing overhead.

Inventive Principle:
Principle #16Partial or excessive action

4Device complexity

If simple signal strength thresholds are used, then processing requirements are reduced, but measurement precision worsens

Engineering Contradiction:
Improveprocessing requirementsVSAvoidmovement detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces dynamic threshold adjustment based on signal strength variations. Instead of using fixed thresholds, the system adapts thresholds based on the specific access point and environmental conditions, improving measurement precision while maintaining simple processing. The thresholds are calculated based on observed signal strength patterns during learning periods.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent performs preliminary learning during which the system collects and analyzes signal strength data to establish baseline thresholds before actual movement detection begins. This preliminary action allows the system to adapt to specific environmental conditions and establish accurate thresholds, improving detection precision without adding complexity to the ongoing detection process.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3804391B1Detecting movement of a computing device based on wireless access point signal strength data and adaptive thresholds
Publication Date: 2025.04.30 MICROSOFT TECHNOLOGY LICENSING LLC
  • EP3804391B1 patent drawingFigure 1
  • EP3804391B1 patent drawingFigure 2
  • EP3804391B1 patent drawingFigure 3

AI summary

The disclosure herein describes receiving wireless signal strength data and detecting movement of a computing device relative to wireless access points based thereon. The computing device receives a signal strength data stream based on a wireless signal from a wireless access point. A signal strength range is determined based on the signal strength data stream during a learning time period while the computing device is within a defined area. The signal strength range indicates that the computing device is within the defined area associated with the wireless access point. During a detection time period, signal strength values outside of the signal strength range are detected and, based on the detected values, a notification is provided that indicates the computing device has moved outside the defined area. The described method provides rapid detection of movements of a computing device using already-obtained data that does not rely on interaction with other devices.