ADS-B Doppler Surveillance for Secure 3D Flight Tracking
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Solution Overview
Problem
The ADS-B system is vulnerable to cyber-attacks due to lack of authentication and encryption, and has coarse data quantization, particularly in vertical speed, necessitating improved systems for aircraft and drone flight surveillance.
Innovation Solution
A system utilizing multiple geographically-distributed collection platforms to accurately measure Doppler shift of ADS-B signals, employing FDOA and TDOA to compute 3D position and velocity vectors, while mitigating transponder instability and clock synchronization errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ADS-B system is used for flight surveillance, then surveillance coverage and data availability are improved, but system vulnerability to cyber-attacks increases due to lack of authentication and encryption
Solution Approach 1:
The patent introduces ground-based multilateration receivers as intermediary devices that independently verify aircraft position through timing measurements of ADS-B signals. These receivers act as mediators between the ADS-B system and ground control, providing cryptographic verification and position validation without requiring modifications to the aircraft transponders, thereby addressing cyber-vulnerability while maintaining surveillance coverage.
Solution Approach 2:
The system implements feedback mechanisms where ground-based receivers continuously monitor and verify ADS-B signal integrity through Time of Arrival (TOA) and Frequency of Arrival (FOA) measurements. This feedback loop enables real-time detection of spoofed or erroneous signals, allowing the system to maintain reliable surveillance by cross-validating position data against multiple independent measurements.
2Device complexity
If traditional ground-based radars are replaced by ADS-B system, then system complexity is reduced, but measurement precision deteriorates due to coarse quantization of data types
Solution Approach 1:
The patent replaces the mechanical/quanized vertical speed measurement system of traditional ADS-B with a physics-based Doppler frequency measurement system. By measuring the frequency shift (FOA) of the ADS-B signal caused by the aircraft's motion, the system derives continuous, high-precision vertical speed data without relying on coarse 64 FPS quantization, thereby substituting a low-precision digital system with a high-precision physical measurement system.
Solution Approach 2:
The system changes the measurement parameter from quantized vertical speed values to continuous frequency of arrival (FOA) measurements. By measuring the Doppler shift in the ADS-B signal frequency, the system obtains continuous vertical speed data with precision far exceeding the original 64 FPS quantization, effectively transforming a discrete parameter system into a continuous parameter system.
3Measurement precision
If multiple geographically-distributed collection platforms are deployed, then measurement precision and cyber security are improved, but device complexity and cost increase
Solution Approach 1:
The patent designs ground-based collection platforms that perform multiple functions simultaneously: TOA measurement for position verification, FOA measurement for velocity and vertical speed extraction, and cryptographic verification for security. This multi-functionality reduces the need for separate specialized devices, thereby managing system complexity while achieving high measurement precision and cyber security through a unified platform architecture.
4Measurement precision
If Doppler shift measurement is used to extract vertical speed, then measurement precision is improved, but difficulty of detecting and measuring increases due to signal processing complexity
Solution Approach 1:
The system uses the aircraft's own transmitted ADS-B signal as the source for Doppler measurement, eliminating the need for separate transmitters or complex external signal generation equipment. By measuring the frequency shift of the signal already being broadcast by the aircraft, the system achieves high-precision vertical speed measurement while minimizing additional hardware and signal processing complexity.
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
Provides hyper-accurate aircraft or drone surveillance, independent of GPS, with enhanced cyber security and meteorological data, and robustness against data dropouts.
Implementation Method 1
accurately measure Doppler shift of ADS-B signals
Data Source
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Figure 3A~3B
AI summary
A system is disclosed for exploiting a transmitted signal from an aircraft (12) to determine characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving. The system includes a plurality of platforms for detecting Doppler shift information of the transmitted signal at each of the plurality of platforms (14, 16, 18), and a processing system (19) for determining characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving.