Abstract
A Multi-Constellation Software-Defined Receiver (MC-SDR) is designed and implemented to extract the Doppler measurements of Low Earth Orbit (LEO) satellite’s downlink signals, such as Orbcomm, Iridium-Next, Globalstar, Starlink, OneWeb, SpaceX, etc. The Doppler positioning methods, as one of the main localization algorithms, need a highly accurate receiver design to track the Doppler as a measurement for Extended Kalman Filter (EKF)-based positioning. In this paper, the designed receiver has been used to acquire and track the Doppler shifts of two different kinds of LEO constellations. The extracted Doppler shifts of one Iridium-Next satellite as a burst-based simplex downlink signal and two Orbcomm satellites as continuous signals are considered. Also, with having the Two-Line Element (TLE) for each satellite, the position, and orbital elements of each satellite are known. Finally, the accuracy of the designed receiver is validated using an EKF-based stationary positioning algorithm with an adaptive measurement matrix. Satellite detection and Doppler tracking results are analyzed for each satellite. The positioning results for a stationary receiver showed an accuracy of about 132 m, which means 72% accuracy advancements compared to single constellation positioning.
Highlights
IntroductionNavigation using Signals of Opportunity (Nav-SOP) has shown enormous potential as an alternative positioning method in Global Navigation Satellite System (GNSS)-challengeable situations
Navigation using Signals of Opportunity (Nav-SOP) has shown enormous potential as an alternative positioning method in Global Navigation Satellite System (GNSS)-challengeable situations.Integration of Inertial Navigation System (INS) and Global Positioning System (GPS) has been one of the most reliable navigation methods in recent decades
One channel of Software-Defined Receiver (SDR) was allocated for Orbcomm with center frequency of 137.5 MHz, and the other channel was determined for Iridium simplex bursts with center frequency of 1626.25 MHz
Summary
Navigation using Signals of Opportunity (Nav-SOP) has shown enormous potential as an alternative positioning method in Global Navigation Satellite System (GNSS)-challengeable situations. Integration of Inertial Navigation System (INS) and Global Positioning System (GPS) has been one of the most reliable navigation methods in recent decades. This method utilizes the short-term accuracy of INS and long-term robustness of GPS at the same time. Some substantial drawbacks of GPS/INS integration methods lead the researchers to focus on the Nav-SOP method, alternatively. Some of the main problems of GPS/INS integration are the possibility of signal interferences, being sensitive to jamming, and inaccessibility in some dense urban and indoor environments. GPS can be blocked or banned in military situations
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