Low-Earth-Orbit Satellite Positioning for Weak Signal Environments
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Solution Overview
Problem
Traditional satellite-based positioning systems, such as GPS, face challenges in weak-signal environments like indoors or urban canyons due to the high altitude and resulting weak signals from medium-earth-orbit satellites.
Innovation Solution
A method and system utilizing low-earth-orbit communication satellite signals, where ground stations with known locations and accurate clocks sample and timestamp signals to determine the ephemeris of communication satellites, and client devices can determine their pseudorange and position using correlation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If medium-earth-orbit satellites are used for positioning, then global coverage is achieved, but signal strength deteriorates due to high altitude and propagation loss
Solution Approach 1:
The patent changes the orbital parameter (altitude) of satellites from medium-earth-orbit to low-earth-orbit, thereby reducing propagation distance and improving signal strength while maintaining global coverage capability through a constellation of satellites
Solution Approach 2:
The patent introduces communication satellites as intermediaries that can operate in both medium-earth-orbit and low-earth-orbit, serving dual purposes of communication and positioning, thereby bridging the gap between global coverage and signal strength requirements
2Area of stationary object
If medium-earth-orbit satellites are used, then positioning system coverage is maintained, but signal attenuation increases in weak-signal environments
Solution Approach 1:
The patent modifies the orbital altitude parameter to low-earth-orbit, which reduces signal attenuation by approximately 20-30 dB compared to medium-earth-orbit, enabling reliable positioning in weak-signal environments such as indoors and urban canyons
Solution Approach 2:
The patent employs a dynamic constellation of low-earth-orbit satellites that continuously move across the sky, ensuring that at least one satellite maintains a favorable geometric position for signal reception in various terrestrial environments
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 approach enables accurate positioning in weak-signal environments by leveraging the stronger and less attenuated signals from low-earth-orbit communication satellites, providing precise location determination and clock offset for client devices.
Implementation Method 1
correlating a set of first samples taken by a first receiver of a transmission from a low-earth-orbit communication satellite with a set of second samples of a replica of transmission to determine a correlation peak
Implementation Method 2
determining a first pseudorange between the first receiver and the low-earth-orbit communication satellite based upon a time different between the correlation peak and the time of transmission
Data Source
AI summary
A positioning system is provided in which a client device samples a transmission from any suitable terrestrial wireless source. The resulting samples are correlated with replica samples to determine a position of the client device using time-difference-of-arrival-based calculations.