Indoor Positioning via Time-of-Flight Trilateration

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Solution Overview

Problem

Current wireless LAN-based location systems suffer from inaccurate indoor positioning due to noisy wireless channels and multipath distortion, leading to significant non-line-of-sight errors that degrade positioning accuracy.

Innovation Solution

A method and system utilizing time-of-flight measurements with ranging protocols, trilateration algorithms, and virtual reference stations to mitigate non-line-of-sight errors, improving positioning accuracy by estimating distances between clients and access points with known positions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If wireless LAN-based location systems are deployed indoors, then location-based services become available, but positioning accuracy deteriorates due to multipath distortion and non-line-of-sight errors

Engineering Contradiction:

Improveavailability of location-based servicesVSAvoidpositioning accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent introduces a location management station as an intermediary component that coordinates ranging protocols between clients and access points. This mediator processes time-of-flight measurements and manages the trilateration calculations, separating the positioning function from the wireless infrastructure itself and enabling accurate indoor positioning through structured measurement coordination

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces traditional mechanical or visual positioning methods with electromagnetic signal-based time-of-flight measurements. By using radio wave propagation time rather than physical measurement or line-of-sight visual methods, the system achieves accurate positioning indoors where GPS and visual methods fail, substituting the measurement mechanism to overcome environmental constraints

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If time-of-flight measurements are used for positioning, then positioning accuracy improves, but the system becomes more sensitive to non-line-of-sight errors from multipath signals

Engineering Contradiction:

Improvepositioning accuracyVSAvoidnon-line-of-sight errors

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements feedback mechanisms where the location management station collects time-of-flight measurements from multiple access points, processes them through trilateration algorithms, and refines position estimates by analyzing consistency across multiple measurement paths. This feedback loop enables the system to identify and compensate for non-line-of-sight errors by comparing measurements from different geometric configurations

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses excessive action by deploying more access points than the minimum required for trilateration and collecting multiple time-of-flight measurements per client. This redundancy allows the system to select the most accurate measurements and discard those affected by multipath distortion, achieving robust positioning despite the presence of harmful non-line-of-sight errors

Inventive Principle:

Principle #16Partial or excessive action

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

The solution effectively minimizes the impact of multipath signals and non-line-of-sight errors, enhancing the accuracy of indoor client location determination in wireless local area networks.

Implementation Method 1

The position location method utilizes the time-of-flight (TOF) measurements of signals transmitted from a client to a number of wireless access points (APs) or vice versa to determine distances.

Methodology Applied

Scientific EffectTime-of-flight measurement: Time of Flight

Data Source

PatentUS8737279B1Method and system for wireless LAN-based indoor position location

Publication Date: 2014.05.27 SIGNAL POINT NETWORKS LLC

AI summary

A method and system for position location of clients in wireless local area networks. (WLANs). The position location technique utilizes time-of-flight (TOF) measurements of signals transmitted from a client to a number of wireless access points (APs) or vice versa to determine distances. Round-trip time (RTT) measurement protocols are used to estimate TOF and distances between the client at an unknown position and the WLAN APs. The method and system improves positioning accuracy by identifying and mitigating non-line-of sight (NLOS) errors such as multipaths. Trilateration algorithms are utilized in combination with median filtering of measurements to accurately estimate the position of the client.