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UNIVERSITY of CALGARY New Enhanced Sensitivity Detection UNIVERSITY OF CALGARY New Enhanced Sensitivity Detection Techniques for GPS L1 C/A and Modernized Signal Acquisition by Surendran K. Shanmugam A DISSERTATION SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF GEOMATICS ENGINEERING CALGARY, ALBERTA January, 2008 c Surendran K. Shanmugam 2008 ISBN: 978-0-494-38222-6 Abstract Throughout history, there has been a constant effort to master the art of navigation for its importance in trade and commerce. Even today, this pursuit of better navigation is still active for its continual impact in various fields. In the last decade, the navigation field witnessed drastic changes with the advent of global navigation satellite system (GNSS) in the form of the global positioning system (GPS). This decade is currently witnessing the expansion of its scope far beyond its traditional focus. On the other hand, these expansions has brought upon new challenges to the current GPS system that were never encountered before. Hence, the legacy GPS system is expected to overcome some stern impediments inherent to these new applications for its continual dominance. For instance, massive signal attenuation, radio frequency interference (RFI) and multipath readily represents, the axis of evil, in the view point of GPS operations as applied to these new applications. More specifically, massive signal attenuation and RFI conditions poses a grave difficulty in terms of traditional GPS operations. Subsequently, one has to resort to enhanced sensitivity GPS receivers for successful GPS operations under these adverse signal conditions. A number of detection algorithms have been utilized to permit successful GPS operations under degraded signal environments. In this dissertation, an earnest effort is made to establish these detection algorithms in a cohesive fashion. Fundamental theoretical considerations based on the generalized likelihood ratio test (GLRT), as applied to GPS signal detection, are discussed. An unified approach is adopted to establish various post-correlation detection schemes as the best approximations of the GLRT. For assumed deterministic signals the GLRT further reduces to a matched filter. This implies that the navigation data, code phase and carrier parameters are known at the receiver. Besides, it unifies the well-known post-correlation non-coherent detection (PCND) and the newly proposed post-correlation differential detection (PCDD) in terms iii iv of GLRT. Finally, new variants of these detection algorithms is proposed both at pre and post-correlation levels. Two asymptotic versions of GLRT, namely the multi-correlation differential detection (MCDD) ( pre-correlation level) and the generalized post-correlation differential detection (GPCDD)(post-correlation level) are proposed. It is shown that the asymptotic version of the GLRT is equivalent to an estimator correlator (EC). The use of a novel pre-filtering operation for pre-correlation noise suppression is also introduced in the context of pre-correlation differential scheme. The benefits of the proposed detectors are further established for interference detec- tion/suppression and modernized GPS signal acquisition. The MCDD based novel contin- uous wave interference detection, estimation, and suppression scheme is introduced. The application of MCDD is also introduced as an efficient detector for GPS L5 NH code acqui- sition in the presence of residual frequency errors. Similarly, the use of GPCDD for GPS L2C acquisition is corroborated in terms of CM and CL code detection. The proposed de- tectors as well as the traditional ones were implemented in MATLABTM environment for subsequent performance analysis. The major findings of the presented research were duly validated using hardware simulated and/or live GPS signals in addition to theoretical and numerical analysis. Acknowledgments It is with pleasure that I acknowledge my heartfelt thanks and gratitude to my doctoral su- pervisors, Professor G´erardLachapelle and Professor John Nielsen for their encouragement, direction, and patience throughout my research. The valuable suggestions of Dr. Cillian O’ Driscoll, Dr. Mark Psiaki and Dr. Abraham Fapojuwo that helped to improve this work are truly appreciated. Special thanks to Dr. Mark Psiaki for his MATLAB based GPS L1 software simulator, which enabled me to further verify various aspects of the results. Dr. Driscoll is further acknowledged for his thoughtful suggestions and great discussions over the past six months. I owe special thanks to Robert Watson, Ccile Mongr´edien,Changlin Ma, Mark Petovello, Kannan Muthuraman, Cyrille Gernot, the TOPS project members and many others in the PLAN research group for their support during the course of my research. I am thankful to Nyunook Kim and Florence Macchi for their assistance during the GPS data collection. I also wish to thank my fellow graduate students and faculty and staff members of the Department of Geomatics Engineering for providing a pleasurable and conducive environment during my studies. iCORE, the University of Calgary Silver Anniversary Graduate Fellowship, the Graduate Faculty Council Scholarship, the Institute of Navigation (ION) National Graduate Scholar- ship, the KIS-94 Graduate Scholarship, ION Student Chapter Award, are acknowledged for their financial support. The Swiss Institute of Navigatio, and the U.S.-based Institute of Navigation are also acknowledged for their student sponsorship, which enabled me to present research papers at their respective conferences. I am thankful to S.K., T.K., Arun Pachai, and Chandru for their excellent support and friendship during my undergraduate years. I also acknowledge to my friends in Calgary, Gopi, Karthik, Angelo, Kumaran, Bala, Vidya, Poorni, Malarvizhi, Leena and others. Very v vi special thanks to Vijayaraghavan for his friendship, support and insightful discussions. I owe very special thanks to my aunt Meenakshi, my brother, Sasi, my sister-in-law Aruna and to a special someone named Saranya. Finally, I am greatly thankful to my family and friends for their immense support. Without their encouragements and understanding, I would not have come this far. vii In loving memory of my mother, Rajalakshmi “The Wind Beneath My Wings” and to my father, Shanmugam “The Good Shepherd” Table of Contents Abstract iii Acknowledgments v Dedications vii Table of Contents viii List of Tables xii List of Figures xiii Notations xvii 1 Introduction 1 1.1 Background . 1 1.2 Relevant Research . 6 1.3 Research Objectives . 14 1.4 Dissertation Outline . 15 2 GPS – Theory, Limitations and Challenges 18 2.1 Historical Evolution . 18 2.2 Legacy GPS Signal Characteristics . 19 2.2.1 Signal Structure . 20 2.2.2 Correlation and Spectral Characteristics . 22 2.2.3 PRN Code Properties . 26 2.3 GPS Digital Receiver Signal Processing . 28 2.3.1 Antenna and Preamplifier . 29 2.3.2 RF Downconversion and Digitization . 30 2.3.3 Baseband Signal Processing . 31 2.4 Software Receiver Implementation . 32 2.5 GPS Limitations – Signal Degradation Effects . 36 2.5.1 Path Loss . 36 2.5.2 Thermal Noise . 37 2.5.3 Interference . 38 2.5.4 Radio Propagation . 39 2.6 High Sensitivity Detection . 41 2.6.1 HS GPS Overview . 44 2.6.2 Limiting Factors of HS GPS . 44 2.7 Discussion . 45 viii ix 3 Enhanced GPS C/A Code Signal Detection – Theory, Analysis and Inno- vations 46 3.1 Signal and Noise Models . 47 3.2 Detection/Estimation Problem in Signal Acquisition . 49 3.3 Optimal Detection – Known Signal Parameters . 56 3.3.1 The Matched Filter Detector . 56 3.3.2 Residual Signal Effects . 59 3.3.3 Limitations of Matched Filter Detector . 66 3.4 Optimal Detection – Unknown Signal Parameters . 67 3.4.1 Incoherent Matched Filter . 69 3.4.2 Post-correlation Noncoherent Detector . 71 3.4.3 Post-correlation Differential Detector . 73 3.4.4 Pre-correlation Differential Detector . 77 3.4.5 GPS Signal Acquisition – Detector Trade offs . 81 3.5 New Generalized Post-Correlation Differential Detector . 82 3.5.1 Loss Due to Data Modulation . 83 3.5.2 Effect of Residual Carrier . 85 3.6 Detection Performance . 87 3.6.1 Coherent Matched Filter . 88 3.6.2 Incoherent Matched Filter . 90 3.6.3 Post-correlation Noncoherent Detector . 91 3.6.4 Post-Correlation Differential Detector . 92 3.6.5 Pre-Correlation Differential Detector . 93 3.6.6 Generalized Post-Correlation Differential Detector . 94 3.7 Acquisition Performance Evaluation . 98 3.7.1 Fine Frequency Estimation Performance . 99 3.7.2 Acquisition Sensitivity Tests . 106 3.7.3 Acquisition Sensitivity – Blind Data Test . 109 3.7.4 Frequency Sensitivity Tests . 119 3.8 Discussion . 123 4 A Novel Pre-Filtering/Multi-correlation Differential Detection Based Ro- bust GPS C/A Code Acquisition 126 4.1 Pre-correlation Noise Suppression . 127 4.1.1 Effect of Residual Frequency Offset . 128 4.1.2 Effect of Navigation Data Modulation . 131 4.1.3 Effect of Pre-Filtering on Standard Detectors . 132 4.1.4 Multi-correlation Differential Detector . 137 4.1.5 Residual Signal Effects . 139 4.1.6 Correlation Performance . 142 4.2 Detection Performance . 150 4.2.1 Multi-correlation Differential Detector . 152 4.3 Acquisition Performance Evaluation . 157 4.3.1 Pre-correlation Noise Suppression Performance . 157 4.3.2 Multi-correlation Differential Detection Performance . 160 x 4.4 Discussion . 171 5 Multi-Correlation Differential Detection Based Interference Detection and Suppression 172 5.1 RF Interference – Sources and Types . 172 5.2 RF Interference Effects and Receiver Trade-offs . 174 5.3 Interference Detection and Suppression . 175 5.4 Effect of Interference on Matched Filter Detector . 177 5.5 Interference Effects on PF/MCDD technique . 181 5.5.1 Multi-correlation Differential Detection . 181 5.5.2 MCDD based CWI Detection, Estimation and Suppression . 182 5.6 Acquisition Performance Evaluation . 186 5.6.1 Test Methodology . 186 5.6.2 Acquisition Sensitivity Tests . 191 5.7 Discussion . 194 6 Modernized GPS Signal Acquisition – New Results 197 6.1 Modernized Signal Structure .
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