Iridium Receiver Positioning with Extended Kalman Filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Global Positioning Systems (GPS) face challenges in determining the position of a user device in environments with diminished signal strength, such as occluded areas or due to radio frequency interference, where GPS signals are unavailable or degraded.
Innovation Solution
A system and method using an Iridium receiver that calculates position and velocity by processing signals from space vehicles, incorporating time and frequency biases, and employing an extended Kalman filter state estimator to maintain track of the user device's position, even in occluded environments, by computing pseudo range and pseudo range rate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS signals are used for position determination, then position accuracy is improved, but signal availability deteriorates in occluded environments
Solution Approach 1:
The patent changes the fundamental parameters of the positioning system by using communication satellites (Iridium) instead of dedicated navigation satellites (GPS). This involves using carrier signals from mobile communication satellites that orbit at lower altitudes (780 km vs 20,000 km), which provides stronger signal strength that can penetrate occluded environments like buildings and tunnels, thereby maintaining signal availability while achieving position determination
Solution Approach 2:
The patent utilizes the dual functionality of communication satellites that serve both as communication relays and as positioning beacons. The same satellite infrastructure used for mobile phone communications is leveraged for navigation purposes, eliminating the need for dedicated navigation satellite receivers and enabling position determination using existing communication satellite signals in environments where GPS is unavailable
2Measurement precision
If time and frequency biases are incorporated in the estimator, then position determination accuracy in occluded environments is improved, but computational complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-modeling and incorporating time and frequency bias parameters into the state vector of the Kalman filter before processing measurements. This allows the estimator to proactively compensate for receiver clock errors and frequency offsets, improving position accuracy in challenging environments without requiring complex post-processing corrections
Solution Approach 2:
The patent implements feedback through the Kalman filter's recursive estimation process, where time and frequency biases are continuously updated based on measurement residuals. The estimator uses the difference between predicted and actual measurements to adjust bias parameters in real-time, creating a self-correcting system that maintains accuracy while managing computational load through efficient recursive updates
Data Source
Figure 1~2
Figure 3a~3b
Figure 4
AI summary
The disclosed method and system is used to determine the position of a user device. The user device can receive data signals and/or carrier signals from orbiting space vehicles. These data signals can be used for positioning calculation and/or track maintenance of the user device. The disclosed method and system can account for time and frequency biases of the user device. For the track maintenance, a Kalman filter state estimator can be extended to include a velocity of the user device.