ADS-B Multi-lateration for GPS Backup Navigation
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Solution Overview
Problem
Global Navigation Satellite Systems (GNSS) like GPS are not reliable in obstructed areas and lack sufficient backup, leading to potential navigation and timing failures in aviation and other critical applications.
Innovation Solution
A technique using Automatic Dependent Surveillance-Broadcast (ADS-B) messages from multiple mobile platforms to determine position and synchronize timing, leveraging Message Start Opportunities (MSO) to calculate signal propagation times and ranges for multi-lateration, providing a reliable alternative to GPS for navigation and timing solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS signals are used for navigation and timing, then positioning accuracy and timing precision are improved, but reliability deteriorates in obstructed areas and during satellite outages
Solution Approach 1:
The system changes the source of timing reference from satellite-based GPS to ground-based cellular network timing signals. By utilizing cellular broadcast messages containing network timing information, the system achieves reliable timing and positioning in obstructed areas where GPS signals are unavailable or unreliable, while maintaining compatibility with existing mobile devices.
2Productivity
If ADS-B surveillance system relies on GPS, then navigation efficiency is improved, but common mode failures occur during GPS outages
Solution Approach 1:
The system introduces cellular network timing signals as an intermediary backup source. When GPS becomes unavailable, the ADS-B surveillance system can switch to using cellular broadcast timing messages to maintain position derivation and timing functions, preventing common mode failures that would otherwise occur during GPS outages.
3Reliability
If ground-based radar systems are used for surveillance, then coverage and backup capability are improved, but navigation capability to aircraft is lost
Solution Approach 1:
The system makes ground-based cellular networks multi-functional by enabling them to provide both surveillance timing reference and navigation positioning capabilities simultaneously. Cellular broadcast messages serve dual purposes: maintaining network synchronization and enabling position derivation for aircraft, thus combining the benefits of ground-based reliability with navigation functionality.
4Reliability
If VOR/DME devices are used for position derivation, then backup navigation capability is provided, but accuracy and coverage are insufficient for reliable aircraft separation
Solution Approach 1:
The system transitions from using traditional VOR/DME ground-based navigation aids to utilizing cellular network timing signals for position derivation. This parameter change enables achievement of GPS-level positioning accuracy using ground-based infrastructure, providing both the reliability of backup capability and the precision required for safe aircraft separation.
Data Source
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AI summary
A technique for determining the position of a mobile device includes receiving messages from respective mobile reference devices. Each of the messages is broadcast beginning at one of several predetermined message start opportunity (MSO) times that have known timings relative to a reference time. Each of the messages contains a MSO value identifying the MSO time at which transmission of the message started. The MSO value is used to determine the time of transmission of each of the messages received at the mobile device, and the position of the mobile device is determined via multi-lateration. According to another approach, the mobile device receives a set of ADS-B messages from a respective set of mobile reference devices. The time of transmission of each of the ADS-B messages is supplied in the ADS-B message itself or in a subsequent message and used to determine the position of the mobile device.