A Software-Defined GPS And Galileo Receiver

Satellite navigation receivers are used to receive, process, and decode space-based navigation signals, such as those provided by the GPS constellation of satellites. There is an increasing need for a unified open platform that will enable enhanced receiver development and design, as well as cost-effective testing procedures for various applications. This book and companion DVD provide hands-on exploration of new technologies in this rapidly growing field. One of the unique features of the work is the interactive approach used, giving readers the ability to construct their own Global Navigation Satellite Systems (GNSS) receivers. To construct such a reconfigurable receiver with a wide range of applications, the authors discuss receiver architecture based on software-defined radio (SDR) techniques. The presentation unfolds in a systematic, user-friendly style and goes from the basics to cutting-edge research. Additional features and topics include: * Presentation of basic signal structures used in GPS and Galileo, the European satellite navigation system * Design and implementation of a GPS signal generator * Presentation and analysis of different methods of signal acquisitiona??serial search; parallel-frequency space search; and parallel-code phase searcha??as well as code/carrier tracking and navigation data decoding * A complete GPS software receiver implemented using MATLAB code as well as GPS and GIOVE-A signal recordsa??available on the companion cross-platform DVDa??allowing readers to change various parameters and immediately see their effects * MATLAB-based exercises * A hands-on method of testing the material covered in the book: supplementary front-end hardware equipmenta??which may be purchased at http://ccar.colorado.edu/gnss a??enables readers working on a Windows or LINUX system to generate real-world data by converting analog signals to digital signals * Supplementary course material for instructors available at http://gps.aau.dk/softgps * Bibliography of recent results and comprehensive index The book is aimed at applied mathematicians, electrical engineers, geodesists, and graduate students. It may be used as a textbook in various GPS technology and signal processing courses, or as a self-study reference for anyone working with satellite navigation receivers.

Preface

ix

List of Figures

xiii

List of Tables

xvii

Abbreviations

xix

1 Signals and Systems

1

(16)

1.1 Characterization of Signals

1

(7)

1.1.1 Continuous-Time Deterministic Signals

2

(1)

1.1.2 Discrete-Time Deterministic Signals

3

(1)

1.1.3 Unit Impulse

3

(1)

1.1.4 Rectangular Pulse

4

(2)

1.1.5 Random Signals

6

(1)

1.1.6 Random Sequence of Pulses

7

(1)

1.2 Sampling

8

(1)

1.3 Characterization of Systems

9

(3)

1.4 Linear Time-Invariant Systems

12

(2)

1.5 Representation of Bandpass Signals

14

(3)

2 GPS Signal

17

(14)

2.1 Signals and Data

17

(1)

2.2 GPS Signal Scheme

18

(2)

2.3 C/A Code

20

(6)

2.3.1 Gold Sequence

20

(1)

2.3.2 Gold Sequence Generation—Overview

21

(1)

2.3.3 Gold Sequence Generation—Details

22

(3)

2.3.4 Correlation Properties

25

(1)

2.4 Doppler Frequency Shift

26

(1)

2.5 Code Tracking

27

(1)

2.6 Navigation Data

28

(3)

2.6.1 Telemetry and Handover Words

29

(1)

2.6.2 Data in Navigation Message

30

(1)

3 Galileo Signal

31

(22)

3.1 Signal Theoretical Considerations

31

(2)

3.2 Galileo Ll OS Signal

33

(9)

3.2.1 Signal Generation

34

(1)

3.2.2 Coherent Adaptive Subcarrier Modulation

35

(2)

3.2.3 Binary Offset Carrier Modulation

37

(5)

3.3 Message Structure

42

(3)

3.3.1 Frames and Pages

42

(1)

3.3.2 Cyclic Redundancy Check

42

(1)

3.3.3 Forward Error Correction and Block Interleaving

43

(2)

3.4 Message Contents

45

(5)

3.4.1 Time and Clock Correction Parameters

46

(2)

3.4.2 Conversion of GST to UTC and GPST

48

(1)

3.4.3 Service Parameters

49

(1)

3.5 The Received Ll OS Signal

50

(3)

4 GNSS Antennas and Front Ends

53

(16)

4.1 Background

53

(2)

4.2 GNSS L1 Front-End Components

55

(9)

4.2.1 GNSS Antenna

55

(2)

4.2.2 Filter

57

(2)

4.2.3 Amplifier

59

(1)

4.2.4 Mixer/Local Oscillator

59

(2)

4.2.5 Analog-to-Digital Converter

61

(3)

4.3 Resulting Sampled Data

64

(2)

4.4 GNSS Front-End ASIC

66

(3)

5 GNSS Receiver Operation Overview

69

(6)

5.1 Receiver Channels

69

(4)

5.1.1 Acquisition

70

(1)

5.1.2 Tracking

71

(1)

5.1.3 Navigation Data Extraction

72

(1)

5.2 Computation of Position

73

(2)

6 Acquisition

75

(12)

6.1 Motivation

75

(1)

6.2 Serial Search Acquisition

76

(2)

6.2.1 PRN Sequence Generation

77

(1)

6.2.2 Carrier Generation

77

(1)

6.2.3 Integration and Squaring

78

(1)

6.3 Parallel Frequency Space Search Acquisition

78

(3)

6.4 Parallel Code Phase Search Acquisition

81

(3)

6.5 Data Size

84

(1)

6.6 Execution Time

85

(1)

6.7 Parameter Estimation

86

(1)

7 Carrier and Code Tracking

87

(22)

7.1 Motivation

87

(1)

7.2 Demodulation

87

(2)

7.3 Second-Order PLL

89

(4)

7.3.1 Damping Ratio

92

(1)

7.3.2 Noise Bandwidth

92

(1)

7.4 Carrier Tracking

93

(3)

7.5 Code Tracking

96

(5)

7.6 Multipath

101

(5)

7.7 Complete Tracking Block

106

(1)

7.8 Pseudorange Computations

107

(2)

8 Data Processing for Positioning

109

(28)

8.1 Navigation Data Recovery

109

(1)

8.1.1 Finding the Bit Transition Time and the Bit Values

109

(1)

8.2 Navigation Data Decoding

110

(4)

8.2.1 Location of Preamble

110

(1)

8.2.2 Extracting the Navigation Data

111

(3)

8.3 Computation of Satellite Position

114

(5)

8.4 Pseudorange Estimation

119

(2)

8.4.1 The Initial Set of Pseudoranges

119

(1)

8.4.2 Estimation of Subsequent Pseudoranges

120

(1)

8.5 Computation of Receiver Position

121

(4)

8.5.1 Time

121

(1)

8.5.2 Linearization of the Observation Equation

122

(1)

8.5.3 Using the Least-Squares Method

123

(2)

8.5.4 Real-Time Positioning Accuracy

125

(1)

8.6 Time Systems Relevant for GPS

125

(2)

8.7 Coordinate Transformations

127

(2)

8.8 Universal Transverse Mercator Mapping

129

(1)

8.9 Dilution of Precision

130

(3)

8.10 World Geodetic System 1984

133

(1)

8.11 Time and Coordinate Reference Frames for GPS and Galileo

134

(3)

Problems

137

(6)

A MATLAB Code

143

(10)

A.1 Structure of the Code

143

(1)

A.2 The settings Structure

144

(1)

A.3 Acquisition Function

145

(2)

A.4 Tracking Function

147

(1)

A.5 Function postNavigation

148

(5)

A.5.1 Pseudorange Computation

149

(1)

A.5.2 Position Computation

150

(3)

B GNSS Signal Simulation

153

(14)

B.1 GPS Signal Simulation

153

(1)

B.2 Simulink Implementation

154

(5)

B.2.1 C/A Code Generation

155

(2)

B.2.2 Navigation Data Generation

157

(1)

B.2.3 P Code Generation

158

(1)

B.2.4 Combining the Signal Components

158

(1)

B.2.5 Upper-Level Implementation

158

(1)

B.3 Galileo Signal Generator

159

(2)

B.4 Differences in Processing GPS and Galileo Signals

161

(3)

B.4.1 Signal Differences

162

(2)

B.5 Differences in Signal Processing

164

(3)

Bibliography

167

(4)

Index

171

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A Software-Defined GPS And Galileo Receiver

Summary

Table of Contents

Supplemental Materials