Satellite Communications

Transcription

1 Satellite Communications Second Edition Timothy Pratt Charles W. Bostian Department of Electrical & Computer Engineering Virginia Polytechnic Institute and State University Jeremy E. Allnutt Department of Electrical & Computer Engineering George Mason University John Wiley & Sons

2 CONTENTS Preface ix 1. Introduction Background A Brief History of Satellite Communications Satellite Communications in Overview of Satellite Communications Summary 16 References Orbital Mechanics and Launchers Orbital Mechanics 17 Developing the Equations of the Orbit 17 Kepler's Three Laws of Planetary Motion 22 Describing the Orbit of a Satellite 23 Locating the Satellite in the Orbit 25 Locating the Satellite with Respect to the Earth 27 Orbital Elements 29 Example Geostationary Satellite Orbit Radius 29 Example Low Earth Orbit 29 Example Elliptical Orbit Look Angle Determination 30 The Subsatellite Point 31 Elevation Angle Calculation 32 Azimuth Angle Calculation 34 Specialization to Geostationary Satellites 35 Visibility Test 36 Example Geostationary Satellite Look Angles Orbital Perturbations 38 Longitudinal Changes: Effects of the Earth's Oblateness 39 Inclination Changes: Effects of the Sun and the Moon 40 Example Drift with a Geostationary Satellite Orbit Determination Launches and Launch Vehicles 43 Expendable Launch Vehicles (ELVs) 44 Placing Satellites into Geostationary Orbit Orbital Effects in Communications Systems Performance 49 Doppler Shift 49 Example Doppler Shift for a LEO Satellite 50 Range Variations 51 Solar Eclipse 51 Sun Transit Outage 53 XI

3 XII CONTENTS 2.7 Summary 54 References 54 Problems Satellites Satellite Subsystems 57 Attitude and Orbit Control System (AOCS) 57 Telemetry, Tracking, Command and Monitoring (TTC&M) 59 Power System 59 Communications Subsystems 59 Satellite Antennas Attitude and Orbit Control System (AOCS) 60 Attitude Control System 60 Orbit Control System Telemetry, Tracking, Command, and Monitoring 68 Telemetry and Monitoring System 68 Tracking 68 Command Power Systems Communications Subsystems 72 Description of the Communications System 72 Transponders Satellite Antennas 80 Basic Antenna Types and Relationships 80 Example Global Beam Antenna 82 Example Regional Coverage Antenna 83 Satellite Antennas in Practice Equipment Reliability and Space Qualification 87 Space Qualification 87 Reliability 88 Redundancy Summary 92 References 93 Problems Satellite Link Design Introduction Basic Transmission Theory 100 Example Example System Noise Temperature and G/T Ratio 105 Noise Temperature 105 Calculation of System Noise Temperature 107 Example Example Noise Figure and Noise Temperature 111 Example G/T Ratio for Earth Stations 112 Example

4 CONTENTS XÜi 4.4 Design of Downlinks 112 Link Budgets 113 Link Budget Example: C-Band Downlink for Earth Coverage Beam Satellite Systems Using Small Earth Stations 117 Direct Broadcast TV 118 Example Uplink Design 124 Example Design for Specified C/N: Combining C/N and C/I Values in Satellite Links 127 Example Overall (C/N) 0 with Uplink and Downlink Attenuation 129 Uplink and Downlink Attenuation in Rain 130 Uplink Attenuation and (C/N) up 130 Downlink Attenuation and (C/N) dn 131 System Design for Specific Performance 131 Satellite Communication Link Design Procedure System Design Examples 132 System Design Example Ku Band Uplink Design 133 Ku Band Downlink Design 134 Rain Effects at Ku Band 135 Summary of Ku Band Link Performance 137 System Design Example Personal Communication System Using Low Earth Orbit Satellites 137 Inbound Link: Mobile Terminal to Gateway Station 141 Mobile Terminal to Satellite Link 142 Satellite to Gateway Station Link 143 Outbound Link 144 Downlink C/N Budget 145 Optimizing System Performance 146 Link Margins with FEC 147 Rain Attenuation at Ku Band 147 Path Blockage at L-Band 149 Summary of L-band Mobile PCS System Performance Summary 150 References 150 Problems Modulation and Multiplexing Techniques for Satellite Links Frequency Modulation 157 Waveform Equation for FM 158 Bandwidth of FM Signals: Carson's Rule 159 Baseband S/N Ratio for FM Signals 159 Pre-emphasis and de-emphasis 161 Pre-emphasis Analog FM Transmission by Satellite 164 Television Signals 165 S/N Ratios for FM Video Transmission 167 Example

5 XIV CONTENTS FM Threshold 168 SCPC FM Links 169 Example Data Transmission Using Analog FM Channels 170 Example Digital Transmission 172 Baseband Digital Signals 172 Baseband Transmission of Digital Data 172 Band-pass Transmission of Digital Data 179 Example Example Transmission of QPSK Signals through a Bandlimited Channel 182 Example Example Digital Modulation and Demodulation 187 Terminology 187 Modulation and Coding 187 Bit and Symbol Error Rates 188 Binary Phase Shift Keying (BPSK) 189 Probability of a Symbol Error 191 BPSK Bit Error Rate 194 QPSK Bit Error Rate 194 Example Example Generation of Quadrature Phase Shift Keying (QPSK) Signals 198 QPSK Variants Digital Transmission of Analog Signals 201 Sampling and Quantizing 201 Nonuniform Quantization: Compression and Expansion 204 Signal-to-Noise Ratio in Digital Voice Systems 206 Digital Television Time Division Multiplexing 209 TDM Terminology: The U.S. Tl 24-Channel System 209 Other TDM Systems 211 Channel Synchronization in TDM Summary 212 References 213 Problems Multiple Access Introduction Frequency Division Multiple Access (FDMA) 223 Intermodulation 226 Intermodulation Example 228 Calculation of C/N with Intermodulation 230 Example Power Sharing in FDMA 231 Example Channel Capacity with Demand Access FDMA Time Division Multiple Access (TDMA) 233 Bits, Symbols, and Channels 234 TDMA Frame Structure 235

6 Example TDMA in a Fixed Station Network 237 Reference Burst and Preamble 238 Unique Word 239 Guard Times 241 Synchronization in TDMA Networks 242 Transmitter Power in TDMA Networks 243 Example TDMA in a VSAT Network 244 Example TDMA in a Fixed Earth Station Network 244 Satellite Switched TDMA Onboard Processing 246 Baseband Processing Transponders 247 Satellite Switched TDMA with Onboard Processing Demand Access Multiple Access (DAMA) 249 Example FDMA-SCPC-DA Random Access Packet Radio Systems and Protocols Code Division Multiple Access (CDMA) 257 Spread Spectrum Transmission and Reception 258 DS-SS CDMA Capacity 262 Example CDMA in a Fixed Earth Station Network 263 Example CDMA in an LEO Satellite Network 263 Example GPS Summary 266 References 267 Problems Error Control for Digital Satellite Links Error Detection and Correction Channel Capacity Error Control Coding 277 Example Linear and Cyclic Block Codes 279 Golay Codes Performance of Block Error Correction Codes Convolutional Codes Implementation of Error Detection on Satellite Links 284 Example Concatenated Coding and Interleaving Turbo Codes Summary 292 References 292 Problems Propagation Effects and their Impact on Satellite-Earth Links Introduction Quantifying Attenuation and Depolarization 298 Example Propagation Effects that Are Not Associated with Hydrometeors 306 Atmospheric Absorption 307 Cloud Attenuation 308

7 XVI CONTENTS Tropospheric Scintillation and Low Angle Fading 308 Faraday Rotation in the Atmosphere 310 Ionospheric Scintillations Rain and Ice Effects 312 Characterizing Rain 312 Rain Climate Maps 314 Rainfall Rate Exceedance Contour Maps 315 Raindrop Distributions Prediction of Rain Attenuation 317 Example Example Calculation of Long-Term Statistics for NGSO Systems 324 Scaling Attenuation with Elevation Angle and Frequency 325 Cosecant Law 325 Example Squared Frequency Scaling Law 326 Example ITU-R Long-Term Frequency Scaling of Rain Attenuation Prediction of XPD 326 Canting Angle 328 Tilt Angle 328 Example Example Ice Crystal Depolarization 332 Rain Effects on Antenna Noise 332 Example Propagation Impairment Countermeasures 333 Attenuation 333 Power Control 334 Signal Processing 335 Diversity 335 Depolarization Summary 338 References 339 Problems VSAT SYSTEMS Introduction Overview of VSAT Systems Network Architectures 347 One-Way Implementation 347 Split-Two-Way (Split IP) Implementation 347 Two-Way Implementation Access Control Protocols 349 Delay Considerations Basic Techniques 354 Multiple Access Selection 355 Signal Formats 362 Modulation, Coding, and Interference Issues 362

8 CONTENTS XVÜ 9.6 VSAT Earth Station Engineering 366 Antennas 366 Transmitters and Receivers Calculation of Link Margins for a VSAT Star Network System Design Procedure: Example Description of System 373 System Parameters 373 Preliminary Calculations 374 Link C/N Ratios 375 Inbound Links 376 Inbound Links with 270 Channels 378 Outbound Links 379 System Analysis Some New Developments Summary 384 References 385 Problems Low Earth Orbit and Non-Geostationary Satellite Systems Introduction Orbit Considerations 391 Equatorial Orbits 391 Inclined Orbits 392 Elliptical Orbits 394 Molniya Orbit 396 Radiation Effects 398 Sun Synchronous Orbit Coverage and Frequency Considerations 406 General Aspects 406 Frequency band 406 Elevation Angle Considerations 408 Number of Beams per Coverage 411 Off-Axis Scanning 412 Determination of Optimum Orbital Altitude 418 Radiation Safety and Satellite Telephones 420 Projected NGSO System Customer Service Base Delay and Throughput Considerations System Considerations 423 Incremental Growth 424 Interim Operations 424 Replenishment Options 424 End-to-End System Implementation Operational NGSO Constellation Designs 425 Ellipso 425 Globalstar 426 New ICO 428 Iridium 428 Orbcomm 429 Skybridge 429

9 XVIII CONTENTS Teledesic 430 Example System Design Summary 434 References 434 Problems Direct Broadcast Satellite Television and Radio C-Band and Ku-Band Home Satellite TV Digital DBS TV DBS-TV System Design DBS-TV Link Budget Error Control in Digital DBS-TV Master Control Station and Uplink Installation of DBS-TV Antennas Satellite Radio Broadcasting Summary 456 References Satellite Navigation and the Global Positioning System Introduction Radio and Satellite Navigation GPS Position Location Principles 463 Position Location in GPS 464 GPS Time GPS Receivers and Codes 467 The C/A Code Satellite Signal Acquisition GPS Navigation Message GPS Signal Levels Timing Accuracy GPS Receiver Operation GPS C/A Code Accuracy 480 Dilution of Precision: HDOP, VDOP, and GDOP Differential GPS Summary 484 References 485 Problems 485 Appendix A Decibels in Communications Engineering 487 Appendix В FDM/FM/FDMA Analog Telephone Transmission 491 Baseband Voice Signal 491 Voice Signal Multiplexing 493 Frequency Modulation with Multiplexed Telephone Signals 496 Bandwidth Calculation for FDM/FM Telephone Signals 497 Telephone Performance Specifications 498 Practical Examples 499 Example B.l 499

10 CONTENTS XiX Example В References 503 Appendix С Complementary Error Function erfc(jr) and Q Function Q(z) 504 Equivalence Formulas and Tables of Values 504 References 504 Appendix D The Simple Attenuation Model 507 Glossary 513 Index 522 Example D.l 511 References 512