SATELLITE COMMUNICATION P. BANERJEE Professor Amity School of Engineering and Technology Amity University, Noida and Former Scientist CSIR–National Physical Laboratory New Delhi Delhi-110092 2017 Contents Preface ........................................................................................................................................... xi Acknowledgements .......................................................................................................................xiii 1. Overview of Satellite Communication .................................................. 1–7 1.1 Introduction 1 1.2 Evolution of Satellite Communication 1 1.3 Historical Development of Satellite Communication 2 1.4 Advantages of Satellite Communication 2 1.5 Growth of Satellite Communication 3 1.6 Frequency Allocation for Satellite Systems 4 1.7 Applications of Satellite Communication 5 Summary 6 Review Questions 7 2. Orbital Mechanics .............................................................................. 8–34 2.1 Introduction 8 2.2 Kepler’s Laws of Planetary Motion 8 2.3 Description of the Orbit of a Satellite 11 2.4 Kepler’s Equation of Motion 14 2.5 Orbital Elements 16 2.5.1 Definitions of Six Orbital Elements 17 2.5.2 Comparison of Orbital Elements 18 2.6 Look Angles 20 2.6.1 Determination of Elevation Angle 20 2.6.2 Determination of Azimuth Angle 21 2.7 Solar Day and Sidereal Day 25 2.8 Time 26 2.8.1 Atomic Clock 26 2.8.2 Calendar 27 2.8.3 Local Time 27 Summary 27 Review Questions 28 Annexure 2A: Conic Section 29 v vi Contents Annexure 2B: Periapsis and Apoapsis 31 Annexure 2C: General Expression of Velocity of a Satellite in an Orbit 32 Annexure 2D: Few Terminologies Related to an Oribit 33 Annexure 2E: Orbit for Interplanetary Flights 34 3. Orbits ............................................................................................... 35–49 3.1 Introduction 35 3.2 Earth’s Oblateness 35 3.3 Atmospheric Drag 37 3.4 Third Body Effects 38 3.5 Radiation Pressure 39 3.6 Earth Coverage 39 3.7 Different Satellite Orbits 41 3.7.1 LEO 41 3.7.2 MEO 41 3.7.3 Geosynchronous Orbits 42 3.8 Highly Eccentric Orbit (HEO): Molniya Orbit 43 3.9 Polar Orbit 45 3.10 Sun-synchronous Orbit 45 3.11 Hohmann Transfer Orbit 46 Summary 47 Review Questions 48 Annexure 3A: Van Allen Radiation Belt 49 4. Launchers ......................................................................................... 50–58 4.1 Introduction 50 4.2 Launch Vehicle 51 4.3 Efficiency of Rocket/Launch Vehicle 52 4.4 Fuel 53 4.5 Launch Sites 53 4.6 Satellite Placement in Geostationary Orbit 54 Summary 55 Review Questions 56 Annexure 4A: Derivation of Ideal Rocket Equation 57 5. Satellite Sub-systems ........................................................................ 59–75 5.1 Introduction 59 5.2 Mechanical Structure 60 5.3 Propulsion Sub-system 60 5.4 Thermal Control 60 5.5 Tracking, Telemetry, Command, and Monitoring 62 5.6 Power Sub-system 63 5.6.1 Solar Cells 64 5.6.2 Total Solar Eclipses for Geostationary Satellites 64 5.6.3 Battery 65 Contents vii 5.7 Attitude and Orbit Control System 66 5.8 Antenna Sub-system 67 5.8.1 Types of Beam Pattern 68 5.9 Communication Sub-system 70 5.10 Space Specification, Reliability and Redundancy 71 5.11 Lifespan of a Satellite 72 5.12 System Configuration of INSAT 72 Summary 74 Review Questions 74 6. The Space Link ................................................................................. 76–98 6.1 Introduction 76 6.2 Calculation of Received Power 77 6.3 System Noise Considerations 81 6.3.1 Noise Temperature 81 6.3.2 Amplifier Noise Temperature 82 6.4 Noise Figure 84 6.5 Carrier-to-Noise Ratio (C/N) 86 6.6 Overall Performance 87 6.7 Antenna Losses 88 6.7.1 Noise Due to Antenna 88 6.7.2 Antenna Pointing Loss 88 6.7.3 Loss Due to Surface Irregularities of Antenna 89 6.8 Propagation Effects 90 6.8.1 Atmospheric Absorption 91 6.8.2 Ionospheric Effects 91 6.8.3 Ionospheric Scintillation 92 6.9 Rain Fade (Rain Attenuation) 92 6.10 Sun Outage 94 6.11 Faraday Rotation 94 Summary 95 Review Questions 95 Annexure 6A: Low Noise Amplifier 96 Annexure 6B: Decibel Units 97 Annexure 6C: Concept of EIRP 98 7. Satellite Access ............................................................................... 99–118 7.1 Introduction 99 7.2 Frequency Division Multiple Access (FDMA) 99 7.2.1 Characteristics of FDMA 102 7.2.2 Overall Carrier-to-Noise Ratio 102 7.3 Time Division Multiple Access (TDMA) 102 7.3.1 TDMA Frame Structure 105 7.3.2 TDMA Frame Efficiency 106 viii Contents 7.3.3 TDMA Superframe 107 7.3.4 TDMA Frame Synchronisation 108 7.4 Code Division Multiple Access (CDMA) 110 7.4.1 PRN Sequence 111 7.4.2 Maximum Number of Users in CDMA 113 7.4.3 Carrier-to-Noise Ratio in CDMA 114 7.5 Spatial Division Multiple Access (SDMA) 114 7.6 Assigning Slots in Multiple Access 114 7.6.1 Pre-assigned (Fixed Assigned) Multiple Access (PAMA or FAMA) 115 7.6.2 Demand Assigned Multiple Access (DAMA) 115 7.6.3 Random Multiple Access (RMA) 116 Summary 116 Review Questions 117 Annexure 7A: Processing Gain 118 8. Global Navigation Satellite System (GNSS) ................................... 119–142 8.1 Introduction 119 8.2 Global Positioning System (GPS) 120 8.3 GPS Constellation 121 8.4 Working Principle of GPS 122 8.5 Signal Structure 123 8.5.1 Generation of the Course Acquisition (C/A) Code 126 8.6 Navigation Data 127 8.7 Navigation Solution 128 8.8 Design of a GPS Receiver 129 8.9 Carrier-to-Noise Ratio of GPS Signal at the Receiving End 130 8.10 GPS Errors 132 8.11 Global Navigation Satellite System (GNSS) 135 8.11.1 GLONASS 135 8.11.2 Galileo 136 8.11.3 BeiDou 136 8.11.4 IRNSS (India) 136 8.11.5 GNSS Comparison 136 8.12 Some Issues Related to GNSS 137 8.12.1 Interoperability and Compatibility 137 8.12.2 Political Decisions 137 8.12.3 Financial Uncertainty 137 8.13 Applications 137 8.13.1 Navigation 137 8.13.2 Surveying, Mapping 138 8.13.3 Precise Time Reference 138 Summary 138 Review Questions 139 Annexure 8A: Least Square Method 140 Contents ix 9. Internet and Satellite Links .......................................................... 143–148 9.1 Introduction to Internet 143 9.2 Layered Structure for TCP/IP 143 9.3 TCP Link 145 9.3.1 Flow Control and Congestion Control 145 9.4 Satellite Links and TCP 146 9.4.1 Round Trip Time (RTT) for Satellite Link 146 9.4.2 Bandwidth-Delay Product (BDP) 146 9.5 Solutions to TCP Problems over Long Delays 147 9.5.1 Split TCP with PEP 147 Summary 148 Review Questions 148 10. Direct Broadcasting Satellite (DBS) Television .............................. 149–163 10.1 Introduction 149 10.2 Digital DBS TV 149 10.3 HDTV Transmission 151 10.4 Compression in Digital TV 151 10.4.1 Necessity of Compression 151 10.4.2 Compression Standards 152 10.5 Reduction in Resolution 153 10.5.1 Colour Sub-sampling 153 10.5.2 Motion Estimation 154 10.5.3 Exploiting Spatial Redundancies 154 10.5.4 Discrete Cosine Transform (DCT) 155 10.5.5 Quantisation 155 10.6 Exploiting Statistical Redundancies 155 10.7 Hybrid Video Encoder 155 10.8 DBS Receiver 156 10.9 Link Budget for FM-FDMA Television 157 10.10 Pre-emphasis and De-emphasis 158 10.11 FM-FDMA Television 159 Summary 160 Review Questions 160 Annexure 10A: Characteristics of Analog TV Signal 161 Annexure 10B: Power Roll-off in dB Scale (dB/Octave) 163 11. Very Small Aperture Terminal (VSAT) ........................................... 164–173 11.1 Introduction 164 11.2 Frequency Allocation 165 11.3 Network Architecture 165 11.3.1 One-way System 165 11.3.2 Split Two-way System 165 x Contents 11.3.3 Broadcast Network 166 11.3.4 Point-to-Point Network 166 11.4 Two-way Network 167 11.5 TDM/TDMA 168 11.6 Trans-receiver in VSAT Network 169 11.7 VSAT or Wireless Local Loop (WLL) Network 170 11.8 Calculation of Link Margin 171 Summary 172 Review Questions 172 12. Special Purpose Satellites ............................................................. 174–178 12.1 Introduction 174 12.2 Globalstar 175 12.3 Iridium 175 12.4 Orbcomm 177 12.5 Landsat 177 12.6 RADARSAT 177 12.7 Indian National Satellite System 177 Summary 178 Review Questions 178 Bibliography ........................................................................................ 179–180 Index ................................................................................................... 181–189 Preface Communication has pervaded into every sphere of life. With the advent of the satellite, communication has become more accessible in almost all parts of the globe. Hundreds of channels we see on our TV are linked through satellites. Mobile phone, e-mail, WhatsApp, net browsing, googling—all are facilitated by communication satellites. Communications via satellites are being so extensively used that the subject ‘satellite communication’ is being taught as one full semester course or at least one or two modules of a semester in electronics and communication engineering department/space department of almost all universities. During the course of my teaching the subject in Amity University, I could realise the difficulties of students in having an in-depth understanding of the subject. I tried to clarify the doubts in my own way. Further, I observed that students could not comprehensively assimilate the subject from any one single book out of many well written and widely referred books available in the market. These observations prompted me to write one compact book, which would adequately address these issues. My notes for taking classes generated over the years have actually been transformed into a presentable form in the shape of this textbook. The contents of the book have also been enriched by my prior research experience of more than three decades in the related field. Most of the chapters are supplemented by one or few annexures that cover presentations of some additional interesting relevant information.