Satellite Position Validation via Time Difference of Arrival

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Solution Overview

Problem

ADS-B aircraft surveillance systems are susceptible to errors in self-reported position information due to intentional spoofing or malfunctions, which can compromise the accuracy of flight tracking and management.

Innovation Solution

A method using satellite-based receivers to validate the self-reported position of aircraft by determining the time difference of arrival (TDOA) of ADS-B messages and calculating a validation distance based on the intersection of a hyperboloid and an ellipsoid, with additional beam-based validation techniques for areas with limited satellite coverage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If self-reported position information is used in ADS-B surveillance systems, then the system operation is simplified and coverage is extended, but the reliability of position data deteriorates due to susceptibility to spoofing and malfunctions

Engineering Contradiction:

Improvesystem operation simplicityVSAvoidposition data reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The system performs preliminary validation of self-reported position data by calculating expected position based on TDOA measurements from multiple satellite receivers before accepting the data for surveillance use. This advance verification prevents unreliable data from compromising system reliability while maintaining operational simplicity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary validation mechanism that acts as a mediator between the self-reported position data and the surveillance system. The TDOA-based position estimation serves as an independent verification layer that mediates the trustworthiness of self-reported positions without requiring changes to the basic ADS-B operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If TDOA-based validation using multiple satellite receivers is implemented, then the reliability of position validation is improved, but the device complexity increases

Engineering Contradiction:

Improveposition validation reliabilityVSAvoidvalidation system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The satellite-based receivers perform multiple functions: they receive ADS-B messages for surveillance and simultaneously perform TDOA measurements for position validation. This multi-functionality reduces the need for separate validation hardware, thereby limiting the increase in device complexity while improving validation reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the existing satellite receiver infrastructure to serve the additional function of position validation. The same receivers that capture ADS-B messages also provide the TDOA data needed for validation, allowing the system to validate positions using its own existing resources rather than requiring separate complex validation equipment.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If beam-based validation is used in areas with limited satellite coverage, then the adaptability of the validation system is improved, but the measurement precision may deteriorate

Engineering Contradiction:

Improvevalidation system adaptabilityVSAvoidposition measurement precision

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

In areas with limited satellite coverage, the system applies partial validation using available beam data rather than requiring complete TDOA validation. This partial action approach maintains adaptability by working with available resources while accepting reduced precision in those specific areas, rather than failing entirely or requiring excessive resources.

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

Enhances the accuracy of aircraft position validation by determining the likelihood of valid self-reported positions, reducing errors and improving the reliability of ADS-B surveillance systems.

Implementation Method 1

determining a time difference between a first arrival time of the RF transmission of the message at the first satellite-based receiver and a second arrival time of the RF transmission of the message at the second satellite-based receiver

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS12105214B2Position validation

Publication Date: 2024.10.01 AIREON LLC

AI summary

In one implementation, a method includes receiving versions of a message from a first satellite-based receiver and a second satellite-based receiver that both received a radio frequency (“RF”) transmission of the message, the message comprising a self-reported position of a transmitter of the message. The method also includes determining a time difference between a first arrival time of the RF transmission of the message at the first satellite-based receiver and a second arrival time of the RF transmission of the message at the second satellite-based receiver. The method further includes determining a measure of the likelihood that the self-reported position of the transmitter is valid based on the time difference between the first and second arrival times. The method still further includes transmitting an indication of the measure of the likelihood that the self-reported position is valid.