THOMAS PANY SOFTWARE RECEIVERS

Transcription

1 TECHNOLOGY AND APPLICATIONS SERIES THOMAS PANY SOFTWARE RECEIVERS

2 Contents Preface Acknowledgments xiii xvii Chapter 1 Radio Navigation Signals Signal Generation Signal Propagation Signal Conditioning Motivation for a Generic Signal Model Sampling Deterministic Received Signal Model Stochastic Noise Model Short-Period Signal Model Zeroth-Order Moment of Signal Power First-Order Moment of Signal Power Second-Order Moment of Signal Power First-Order Moment of Signal Power Variations Separation of Code and Carrier Correlation Exemplary Signals A Model for the GPS C/A-Code Signal A Model for the Galileo E1 Open-Service Signal Pulsed GNSS Signals Gaussian Double Pulse 15 References 16 Chapter 2 Software-Defined Radio Definitions Communication Radios GNU Radio Joint Tactical Radio System GNSS Software Receivers Front Ends Illustrative Applications High-End GNSS Software Receivers Technology Evaluation and Discussion 30 References 30

3 vi Contents Chapter 3 GNSS Receiver Structure and Dataflow GNSS Sample Handling Real-Time Mode Postprocessing Mode Module Diagram USB Front-End Driver IF Sample Buffer Sensor Interface Postprocessing Mode Master Receiver Receiver Master Channel Channel Acquisition Manager Level-1 and Level-2 Acquisitions Navigation Processor Positioning with RAIM Navigation Modules Input and Output Modules Receiver Status Navigation Records AGNSS and SISNET Connection Execution Flow Computer with Four CPU Cores Computer with a Single CPU Core GNSS Reference Station Configuration Acquisition Parameters Tracking Parameters Performance Results Discussion 54 References 55 Chapter 4 Signal Estimation Parameters of Interest Useful Parameters Nuisance Parameters Relationship Between the Parameters Nonrandom Parameter Estimation Position CRLB Without Nuisance Parameters Position Estimation with Nuisance Parameters Single-Step Maximum Likelihood Estimation Cascaded Estimation LSQ Correlators/Discriminators 72

4 Contents vii Model for One or More Propagation Paths Single Propagation Path Correlation Point Linearization Multiple Propagation Paths Two Propagation Paths: Code-Phase CRLB Two Propagation Paths: Doppler CRLB Two Propagation Paths: Remark on Other Bounds Data Reduction Sufficient Statistics Multicorrelator Approach First-Derivative Approach Colored Noise Bayesian Approach Minimum Mean-Squared Error Estimation Kalman Bucy Filter Other Filters Use of Kalman Filters in GNSS Signal Processing Squaring Loss Revisited Numerical Simulation Evaluation of Bounds Cost Function LSQ Solution Discussion 124 References 125 Chapter 5 Signal Detection Detection Principles Simple Hypothesis Testing Composite Hypothesis Testing Detection Domains Pseudorange Domain Detection Position Domain Detection Preprocessing Clairvoyant Detector for Uniformly Distributed Phase Energy Detector Bayesian Detector Generalized Likelihood-Ratio Detector Single Coherent Integration Multiple Coherent Integrations Considering Navigation Signal Interference Data and Pilot System-Detection Performance Idealized Assumptions Mean Acquisition Time 155

5 viii Contents System Probabilities Independent Bin Approximation Code-Phase and Doppler Losses Long Integration Times and Differential Detectors Discussion 159 References 161 Chapter 6 Sample Preprocessing ADC Quantization Quantization Rule Matched Filter Evaluation of Expected Values Infinite Number of Bits Numerical Evaluation Noise-Floor Determination ADC Requirements for Pulse Blanking Front-End Gain and Recovery Time Pulse Blanking ADC Resolution Handling Colored Noise Spectral Whitening Modified Reference Signals Overcompensation of the Incoming Signal Implementation Issues Sub-Nyquist Sampling 180 References 182 Chapter 7 Correlators Correlator and Waveform-Based Tracking Generic Correlator Expected Value Covariance Variance Correlator Types with Illustration P-Correlator F-Correlator D-Correlator W-Correlator Difference Correlators Single-Difference P-Correlators Double-Difference P-Correlators Noisy Reference Signal for Codeless Tracking Expected Value Covariance 202

6 Contents ix Variance L2 P(Y)-Code Carrier-Phase Discriminator Noise Incorporating Colored Noise White-Noise Transformation Early Late Code Discriminator with Infinite Sample Rate Comparison of Finite and Infinite Sample Rates 212 References 214 Chapter 8 Discriminators Noncoherent Discriminators Code Discriminator Doppler Discriminator Phase Discriminator Clipping S-Curve Shaping Code-Discriminator Performance Characteristics Optimum S-Curve Frequency-Domain S-Curve Shaping Discussion Multipath Estimating Techniques The LSQ Equations Calibration General Procedure Correlator Placement Initial Values Number of Required Iterations Multipath Detection Discussion From Discriminator Noise to Position Accuracy 238 References 239 Chapter 9 Receiver Core Operations Test-System Configuration Signal-Sample Bit Conversion Algorithm Numerical Performance Discussion and Other Algorithms Resampling Algorithm Numerical Performance NCO Resolution Discussion and Other Algorithms Correlators SDR Implementation 249

7 x Contents Discussion and Other Algorithms Fast Fourier Transform Algorithm Convolution Theorem Time-Domain Correlation and Data Preparation Spectral Shifting Limited-Size Inverse FFT Circular Correlation with Doppler Preprocessing Handling Secondary Codes Asymptotic Computational Performance Reported FFT Performance Values Discussion and Number of Correlators Reality Check for Signal Tracking Power Consumption Discussion 274 References 275 Chapter 10 GNSS SDR RTK System Concept Technology Enablers Ultra-Mobile PCs Cost-Effective High-Rate Data Links System Overview Setup Sample Applications Test Installation and Used Signals Key Algorithms and Components High-Sensitivity Acquisition Engine Doppler Search Space Correlation Method Clock Stability Line-of-Sight Dynamics Flow Diagram and FFT Algorithms Acquisition Time Assisted Tracking Vector-Hold Tracking Double-Difference Correlator Low-Cost Pseudolites Continuous-Time Signals Pulsed Signals RTK Engine 304 References 305 Chapter 11 Exemplary Source Code Intended Use 307

8 Contents xi 11.2 Setup Required Software Preparing the Simulation Signal Selection and Simulation Parameters Routines True Cramér-Rao Lower Bound Discriminator Noise Analysis FFT Acquisition Simplified Vector Tracking with Multipath Mitigation and Spectral Whitening 309 Appendix A.1 Complex Least-Squares Adjustment 311 A.1.1 Definitions 311 A.1.2 Probability Density Function 312 A.1.3 The Adjustment 312 A.1.4 Real- and Complex-Valued Estimated Parameters 314 A.1.5 A Posteriori Variance of Unit Weight 315 A.1.6 Example 318 A.1.7 Discussion 320 A.2 Representing Digital GNSS Signals 320 A.2.1 Complex-Valued Input Signal 320 A.2.2 Real-Valued Input Signal 321 A.2.3 Comparing Real- and Complex-Valued Signals 322 A.3 Correlation Function Invariance 326 A.4 Useful Formulas 329 A.4.1 Fourier Transform 329 A.4.2 Correlation Function 331 A.4.3 Correlation with an Auxiliary Function 332 A.4.4 Correlation with Doppler 333 A.4.5 Correlation in Continuous Time 334 A.4.6 Probability Density Functions 336 References 338 Abbreviations 339 List of Symbols 343 About the Author 345 Index 347