Asynchronous Localization Using Signals of Opportunity
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Solution Overview
Problem
Current positioning methods, particularly for military and GPS-denied environments, face challenges such as signal degradation, jamming, and loss of line-of-sight, which hinder accurate navigation and localization.
Innovation Solution
A novel asynchronous localization method using Signals of Opportunity (SoOPs) from unsynchronized transmitters and receivers, allowing for cooperative network-based positioning without the need for synchronization, utilizing Time Difference of Arrival (TDOA) and Time of Flight (TOF) measurements from multiple SoOP transmitters to determine node positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS synchronous positioning is used, then positioning accuracy is improved, but system reliability deteriorates due to signal vulnerability to jamming and line-of-sight blockage
Solution Approach 1:
The patent converts the harmful effect of GPS signal jamming and blockage into a beneficial alternative positioning method. By using asynchronous TDOA with terrestrial transmitters, the system transforms the problem of GPS unavailability into an opportunity to use robust, jam-resistant terrestrial signals for positioning, thereby maintaining reliability while achieving acceptable accuracy
Solution Approach 2:
The patent changes the fundamental timing parameter from synchronous (GPS) to asynchronous operation. By removing the synchronization requirement and using relative time differences between unsynchronized receivers, the system achieves GPS-like positioning capability without the vulnerability to jamming and line-of-sight blockage, resolving the contradiction between accuracy and reliability
2Device complexity
If asynchronous positioning with unsynchronized transmitters is used, then system complexity is reduced, but measurement precision deteriorates due to lack of timing information
Solution Approach 1:
The patent introduces an intermediary reference transmitter with known location and asynchronous TDOA calculation as a mediator between unsynchronized receivers and positioning accuracy. The reference transmitter provides a common reference signal that all receivers can use to calculate relative time differences, enabling precise positioning without requiring the receivers to be synchronized to each other
Solution Approach 2:
The patent replaces the mechanical synchronization system (clock synchronization between transmitters and receivers) with an asynchronous measurement system. Instead of requiring precise clock synchronization, the system uses time difference of arrival measurements relative to a reference transmitter, substituting complex synchronization mechanics with simpler asynchronous measurement and calculation
3Reliability
If multiple nodes are required for positioning, then positioning robustness is improved, but device complexity increases due to node coordination requirements
Solution Approach 1:
The patent segments the positioning problem into independent node pairs, where each pair performs autonomous TDOA measurements without requiring coordination with other pairs. This segmentation allows multiple nodes to contribute to positioning robustness while avoiding the complexity of coordinating all nodes together, as each pair operates independently with the same reference transmitter
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
This method provides robust, scalable, and cost-effective positioning in GPS-degraded or denied environments, requiring minimal nodes and transmitters, and can adapt to various scenarios like urban, forested, or space environments, with the ability to synchronize clocks using fewer satellites.
Implementation Method 1
utilizing Time Difference of Arrival (TDOA) and Time of Flight (TOF) measurements from multiple SoOP transmitters to determine node positions
Data Source
AI summary
A new asynchronous localization method for a network of nodes and transmitters, the position of at least one of the nodes and/or transmitters being known, involves receiving a first signal directly from a first transmitter at a first node of a first node pair, receiving the first signal relayed from a second node of the first node pair at the first node, and determining the delay at the first node between the direct and relayed first signal by comparing the direct and relayed first signals. This may be repeated with the first node acting as relay to determine the delay at the second node. Time difference of arrival and/or time of flight between first and second nodes may be determined using the determined delay at the first and/or second node and/or known node locations. The process is repeated for additional transmitters/node pairs until sufficient information is determined for desired applications.