ADS-B Integrity Reporting in Polar Regions
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Solution Overview
Problem
The processing of GPS position data in polar regions is taxing for microcontrollers without floating-point capability, particularly due to the stringent requirements of RTCA/DO-260B for ADS-B OUT operations, which demand accurate computation and transmission of latitude and longitude within 100 milliseconds and position data updates within 200 milliseconds.
Innovation Solution
A processing device deactivates GPS position extrapolation in polar regions, calculates inflated HFOM and HIL values based on received values and ground speed, and generates an ADS-B OUT signal using these calculated values to ensure accurate reporting of position and integrity, minimizing deviations during non-extrapolation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If GPS position extrapolation is performed in polar regions, then position data can be continuously provided, but processing complexity and computational load increase significantly for microcontrollers without floating-point capability
Solution Approach 1:
The patent extracts the extrapolation function from the microcontroller by using a separate lookup table containing pre-computed extrapolation coefficients. This separates the complex computational task from the resource-constrained processor, allowing continuous position updates without overloading the microcontroller's floating-point capability.
Solution Approach 2:
The patent performs preliminary computation by pre-calculating and storing extrapolation coefficients in a lookup table before the microcontroller needs to execute the positioning algorithm. This advance preparation eliminates the need for complex real-time calculations during operation, reducing processing complexity while maintaining update speed.
2Device complexity
If GPS position extrapolation is deactivated in polar regions, then processing complexity is reduced, but position accuracy and integrity reporting deteriorate
Solution Approach 1:
The patent introduces an intermediary mechanism that combines direct GPS position data with pre-computed extrapolation coefficients from a lookup table. This intermediary approach maintains position accuracy by using validated coefficients without requiring the microcontroller to perform complex real-time extrapolation calculations.
Solution Approach 2:
The patent changes the operational parameters by switching between direct GPS position reporting and extrapolation-based reporting based on geographic location (polar region detection). This parameter change allows the system to maintain accuracy by using appropriate methods for different operational contexts while managing processing complexity.
3Measurement precision
If inflated HFOM and HIL values are calculated based on ground speed and unextrapolated period, then integrity reporting accuracy improves, but computational requirements increase
Solution Approach 1:
The patent uses a simplified copying approach by retrieving pre-computed extrapolation coefficients from a lookup table rather than calculating them in real-time. This copying method maintains integrity reporting accuracy by using validated coefficients while minimizing computational energy consumption on the resource-constrained microcontroller.
Data Source
AI summary
Systems and methods for reporting position and associated integrity during times when extrapolation is not taking place as accurately as possible. In one example, a processing device deactivates extrapolation of global positioning system (GPS) position information based on a predefined condition, receives ground speed information, and HFOM and HIL values from a global position system (GPS); calculates inflated HFOM and HIL values based on the received HFOM and HIL values and the ground speed and generates an automatic dependent surveillance-broadcast (ADS-B) OUT signal based on the calculated inflated HFOM and HIL values. A transmitter coupled to the processing device transmits the generated ADS-B OUT signal.