Development of the Low Earth Orbit Satellite Signal Aided GPS Positioning

Abstract

GPS adopts spreading spectrum technology which effectively reduces the power consumption at the transmission but the corresponding weak power signal can be blocked easily in challenging environments In a city near mountains or indoors GPS cannot promise continuous positioning services at all From this perspective an LEO satellite communication system with stronger signal power and higher dynamics is introduced to aid the GPS positioning The wider Doppler shift range due to the high dynamics of LEO satellites causes enough trouble for the conventional GPS receiver that normal processing cannot guarantee on-time solutions for the positioning computation On the other hand acquisition information is not easy to obtain either Inspired by TRANSIT the first generation of satellite navigation system in this thesis the Doppler shift substitutes the pseudorange as the measurement and the Doppler effect is applied for aiding in positioning The main goal of this research is to develop an aiding positioning system using the Doppler shift of an LEO signal and to study its feasibility The aiding positioning system which combines the pseudorange information of the GPS system and the Doppler shift information of the LEO system for simultaneous calculation includes two cores: the LEO signal processing and a combined positioning algorithm using the trilateration and Doppler positioning In the thesis the IRIDIUM network the satellite communication system of the Boeing Company is the target LEO aiding positioning system Its physical architecture signal structure local observation worldwide availability analysis and signal processing are detailed in the content In the algorithm two original algorithms the trilateration and the Doppler positioning are firstly introduced then the derivation of the combined positioning algorithm follows In the confirmation and the demonstration of the developed aiding positioning system the experiments are designed as in a city environment and the results are compared to the conventional Trilateration-only positioning The analysis shows the LEO aiding positioning system performance to be no worse than ordinary GPS positioning

Date of Award	2014 Sept 3
Original language	English
Supervisor	Shau-Shiun Jan (Supervisor)