Wireless Location Tag Interference Detection and Power Control

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Solution Overview

Problem

Existing location systems face challenges in providing high reliability and accuracy for real-time location tracking of assets or persons in large, complex environments like hospital buildings, particularly due to interference from devices emitting low-frequency signals and the need for precise room identification.

Innovation Solution

A wireless location system incorporating a short-range exciter transmitter that broadcasts continuous messages with identification numbers, and an identification tag that responds with WLAN messages, including telemetry data, to accurately determine location while mitigating interference through alert mechanisms and adjustable exciter output power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If exciter transmits continuous beacon signals to enable real-time location tracking, then location accuracy is improved, but interference from low-frequency signals increases

Engineering Contradiction:

Improvelocation accuracyVSAvoidinterference from low-frequency signals

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The exciter transmits beacon signals periodically rather than continuously, which reduces the overall signal interference in the environment while still enabling the tag to receive signals and report location accurately at regular intervals

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system includes an alert mechanism that detects interference conditions and responds by adjusting exciter output power or triggering notifications, thereby converting the harmful interference into a controllable parameter that maintains location tracking reliability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If exciter output power is increased to improve signal coverage and location detection reliability, then location tracking reliability is improved, but interference effects increase

Engineering Contradiction:

Improvelocation tracking reliabilityVSAvoidinterference effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The exciter output power is made dynamically adjustable rather than fixed, allowing the system to optimize the balance between coverage/reliability and interference by varying power levels based on detected interference conditions and location tracking requirements

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system includes interference detection and alert mechanisms that provide feedback to the control system, which then adjusts exciter output power accordingly to maintain reliability while minimizing interference effects

Inventive Principle:

Principle #23Feedback

3Speed

If the system uses RSSI or TOA measurements to calculate tag location, then real-time location tracking is achieved, but measurement precision deteriorates in environments with interference

Engineering Contradiction:

Improvereal-time location trackingVSAvoidlocation measurement precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The system uses WLAN access points and location receivers as intermediary devices that facilitate accurate location measurement by providing multiple signal paths and measurement points, thereby improving precision even in the presence of interference

Inventive Principle:

Principle #24Intermediary (Mediator)

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 system ensures high reliability and accuracy in tracking assets or persons within large areas by minimizing interference effects and providing real-time location data, enabling secure access control and enhanced monitoring.

Implementation Method 1

a low frequency transmitter (sometimes referred to as an 'exciter'), which periodically transmits a beacon signal

Methodology Applied

Scientific EffectElectromagnetic radiation: Electromagnetic Induction

Implementation Method 2

an RFID tag that transmits RF signals on a WLAN channel

Methodology Applied

Scientific EffectRadio frequency transmission: Electromagnetic Induction

Implementation Method 3

typically done using RSSI (receive signal strength indication) or TOA (time of arrival) measurements of the radio signal

Methodology Applied

Scientific EffectTime of arrival measurement: Time of Flight

Implementation Method 4

RSSI (receive signal strength indication) or TOA (time of arrival) measurements

Methodology Applied

Scientific EffectSignal strength indication:

Data Source

PatentEP2876579B1Identification tag and location system

Publication Date: 2018.12.26 AEROSCOUT

Figure 1
Figure 2

AI summary

An identification tag has at least a controller, a receiver for receiving wireless signals from an exciter, and a transmitter for transmitting wireless signals to at least one location receiver (which may be a WLAN access point). The tag's controller can determine the presence of interference from sources unrelated to the location system, such as smartphones, tablets, computer monitors etc., and signal an alert accordingly.