High-Altitude Platforms for Wireless Communications

Table of Contents:
Preface xiii 1 Introduction 1 1.1 What is a HAPS? 1 1.2 Structure of the Book 3 References 4 2 Overview on HAPS 5 2.1 HAPS System Concepts 5 2.1.1 HAPS Definition and Features 5 2.1.2 Components of HAPS Communication Systems 7 2.1.2.1 Stratospheric Segment 7 2.1.2.2 Ground Segment 8 2.2 Radio Regulations for HAPS 9 2.3 Applications and Services 11 2.3.1 Selection of Possible Applications 11 2.3.2 Application and Service Requirements 12 2.3.3 Narrowband Services 12 2.3.4 Broadband Services 13 2.4 HAPS Networks 14 2.5 Terrestrial, Satellite and Stratospheric Communication Systems: A Comparison 15 2.6 Survey of the Evolution and State-of-the-Art of HAPS in the World 17 2.6.1 North American HAPS Projects 17 2.6.1.1 SHARP 17 2.6.1.2 Sky Station 20 2.6.1.3 HALO-Proteus 21 2.6.1.4 Pathfinder, Pathfinder Plus, HELIOS, SkyTower 21 2.6.2 European Projects and Activities on HAPS 23 2.6.2.1 HALE 24 2.6.2.2 STRATOS 24 2.6.2.3 HeliNet 25 2.6.2.4 CAPANINA 26 2.6.2.5 COST 297 – HAPCOS 27 2.6.2.6 USE HAAS 29 2.6.2.7 European Union Research Thematic Networks 29 2.6.3 Asia-Pacific Projects and Activities on HAPS 30 2.6.3.1 Japanese Activities 30 2.6.3.2 Korean Activities 31 2.6.3.3 International Cooperation Activities in Malaysia 32 References 33 3 Propagation and Channel Modelling 37 3.1 Introduction 37 3.2 An Overview of Propagation Phenomena 38 3.2.1 Free Space Loss 38 3.2.2 Multipath 38 3.2.3 Rain Attenuation 41 3.2.4 Gaseous Absorption 42 3.2.5 Scintillation 44 3.3 Channel Modelling 48 3.3.1 Geometric Characterisation 49 3.3.2 Statistical Characterisation 52 3.3.3 UHF Channel Models 55 3.3.3.1 Wideband Models 55 3.3.3.2 Switched-Channel Models 58 3.3.3.3 Markov Chains 59 3.3.3.4 Lutz Model 62 3.3.3.5 Semi-Markovian Processes 64 3.3.3.6 Switched Broadband Channel Models 66 3.3.3.7 Politecnico di Torino (Polito) Multipath Channel Model 69 3.3.4 SHF Channel Models 70 3.3.4.1 Clear Sky 70 3.3.4.2 Rain 72 3.3.4.3 Time Series 77 3.4 Fading Mitigation Techniques 82 3.4.1 Power Control 84 3.4.1.1 Uplink Power Control 84 3.4.1.2 Downlink Power Control 85 3.4.1.3 On-board Beam Shaping 86 3.4.2 Adaptive Methods 86 3.4.2.1 Adaptive Coding 86 3.4.2.2 Adaptive Modulation 87 3.4.2.3 Digital Transmission Rate Reduction 91 3.4.3 Diversity 91 3.4.3.1 Site Diversity 91 3.4.3.2 Platform Diversity 92 3.4.3.3 Frequency Diversity 92 3.4.3.4 Time Diversity 93 3.4.4 Fading Detection 94 3.4.4.1 Open Loop 94 3.4.4.2 Closed Loop 94 3.4.4.3 Hybrid Loop 95 3.5 Conclusions 95 References 95 4 Antennas for HAPS 99 4.1 Introduction 99 4.2 Antenna Requirements 100 4.2.1 Physical Requirements 100 4.2.2 Gain, Directivity and Efficiency 102 4.2.3 Sidelobe Performance 104 4.2.4 Footprint 104 4.2.5 Beam Steering 105 4.2.6 Scan Range 106 4.2.7 Coverage Area 107 4.2.8 Multiple Beam Functionality 107 4.2.9 Operating Frequency 107 4.3 Antenna Types for High-Altitude Platforms 108 4.3.1 Phased-Array Antennas 108 4.3.2 Aperture Antennas 110 4.3.2.1 Lens Antennas 110 4.3.2.2 Parabolic Reflectors 113 4.3.2.3 Horn Antennas 116 4.3.3 Broadband Printed Array Antennas 116 4.3.4 Smart (Adaptive) Antennas 119 4.4 Antenna Design Recommendations at Operating Frequencies Allocated to HAPS 120 4.4.1 Antennas for IMT-2000 Frequency Band (2.1 GHz) 120 4.4.2 Antennas for the Ka Frequency Band (27/31 GHz) 122 4.4.3 Antennas for the 47/49 GHz Frequency Band 124 4.5 Steering Mechanisms 124 4.5.1 Axis Control Gimbals 125 4.5.2 Antenna Positioning Systems 126 4.5.3 Research on Antenna Gimbals 127 4.6 Beamforming 128 4.6.1 HAPS-Based Beamforming 129 4.6.1.1 Adaptive Methods 129 4.6.1.2 Non-adaptive Methods 130 4.6.2 Ground-Based Beamforming 136 4.7 Challenges 136 References 137 5 Communication Systems Based on HAPS 141 5.1 Components of HAPS Communication Systems 141 5.1.1 Stratospheric Segment 141 5.1.1.1 Platforms 142 5.1.1.2 Telecommunications Payload 143 5.1.1.3 Telemetry, Tracking and Command 146 5.1.1.4 Attitude and Stabilisation Control 148 5.1.1.5 Electrical Power Subsystem 150 5.1.2 Ground Segment 153 5.1.2.1 Antennas 154 5.1.2.2 Low-noise Amplifier 154 5.1.2.3 High-power Amplifier 154 5.1.2.4 Software 154 5.1.2.5 People 155 5.2 Spectrum Allocation for HAPS 155 5.3 HAPS Link Budget 159 5.3.1 Uncoded Digital Transmission Analysis 160 5.3.1.1 Uplink 162 5.3.1.2 Transponder 163 5.3.1.3 Downlink 164 5.3.2 Coded Digital Transmission Features 164 5.3.3 IMT-2000 (2.1 GHz) Link Budgets 167 5.3.3.1 HAPS for IMT-2000 Systems 167 5.3.3.2 CDMA HAPS Link Budget for Voice 171 5.3.3.3 CDMA HAPS Link Budget for High-Speed Data Services 174 5.3.4 Ka-Band (27/31 GHz) Link Budgets 174 5.3.4.1 Clear Sky 177 5.3.4.2 Rain 179 5.3.5 SHF-Band (47/49 GHz) Link Budget 179 5.3.5.1 Frequency Planning 181 5.3.5.2 Transmission Characteristics of the Platform Station 182 5.3.5.3 User Terminals and Ground Stations 182 5.3.5.4 Radioelectric Emission Characteristics of HAPS Communication Systems 182 5.3.5.5 Link Budget Analysis 183 5.3.6 Link Budget Comparison 184 5.4 Conclusions 185 References 185 6 HAPS Networks 189 6.1 Introduction 189 6.2 Network Topologies 189 6.2.1 Point-To-Point Deployment Topology 190 6.2.2 Point-To-Multipoint Deployment Topology 190 6.2.3 Multipoint-To-Multipoint Deployment Topology 191 6.2.4 Hybrid Deployment Topology 191 6.3 Network Architectures for Service Candidates 192 6.3.1 Ring-Shaped Cell Clustering 192 6.3.2 Cell Scanning 193 6.3.3 Multiple-Beam Mobile Platform Scenario 193 6.3.4 Macrocell–Microcell–HAPS Topology 193 6.3.5 Cell Sectorisation Architecture 194 6.3.6 Standalone Platform 195 6.3.7 Network of Platforms Connected Via Ground Stations 196 6.3.8 Network of Platforms Connected Via Interplatform Links 197 6.3.9 Integrated Terrestrial–HAPS–Satellite Networks 198 6.3.9.1 Use of HAPS for Interactive Digital Broadcast System 200 6.3.9.2 Symmetric DVB-RCH Configuration 200 6.3.9.3 Asymmetric DVB-RCH Configuration 200 6.4 Interworking Requirements 201 6.4.1 Cell Planning 202 6.4.2 Call Admission Control 203 6.4.3 Handover Issues 203 6.5 HAPS Networks for Other Applications 204 6.5.1 Navigation 204 6.5.2 Emergency Services 205 6.6 Free Space Optical Links in HAPS 206 6.6.1 Stratospheric Relay and Integrated Satellite–HAPS Using Optical Links 206 6.6.2 Optical Satellite Downlinks for Earth Observation Satellites Using HAPS 208 6.7 Resource Management 208 6.7.1 Resource Allocation 208 6.7.1.1 Area-Based Fixed Channel Assignment Scheme 209 6.7.1.2 Uniform Fixed Channel Assignment Scheme 209 6.7.2 Call Admission Control 210 6.7.3 Medium Access Techniques 211 6.8 HAPS as Part of Integrated Communication Networks 212 6.8.1 2G Cellular Systems: GSM 212 6.8.2 3G Cellular Systems: IMT-2000 213 References 213 7 The Future 217 7.1 Introduction 217 7.2 Challenges and Opportunities for Civil UAS 218 7.3 Applications for Civil UAS 219 7.3.1 General Applications 219 7.3.2 Telecommunications Applications 220 7.4 Requirements for the Future of the Civil UAS 222 7.4.1 Aeronautical Regulations 222 7.4.2 Spectrum Regulation 223 7.5 Technological Trends 224 7.5.1 Platform Technologies 224 7.5.2 Telecommunications Technologies 226 7.6 Technological Challenges for HAPS Applied to Wireless Communications 227 7.6.1 Radiowave Propagation Models at Millimetre-Wave Bands 227 7.6.2 Fade Mitigation Techniques 227 7.6.3 Forward Error Control and Modulation Techniques 227 7.6.4 Interference Management 228 7.6.5 Handover Issues 228 7.6.6 In-Building Penetration 228 7.6.7 Networking Issues 228 7.6.8 Antenna Technology 229 7.7 Conclusions 229 References 230 Glossary 233 Index 237

About the Author :
Dr. Aragón-Zavala graduated from Tecnológico de Monterrey, Campus Querétaro as Electronics and Communications Engineer in December 1991. In 1998 he received his MSc in Satellite Communication Engineering from the University of Surrey, and in 2003 his PhD in Antennas and Propagation at the same university. He has worked as an engineer and consultant in the industry, and since 2003, Dr. Aragón-Zavala is the Academic Director of the former IEC and ISE undergraduate programs at the Tecnológico de Monterrey Campus Querétaro, and is in charge of ITE (all Electronic Engineering degrees). His research interests include: mobile communications, satellite systems, high-altitude platform systems, antenna design and indoor propagation. Dr José Luis Cuevas-Ruiz received his PhD from Universitat Politecnica de Catalunya in 2005, where he was involved in the HeliNet and CAPANINA projects related to high-altitude platform systems. His research interests include HAPS, wireless communications and channel modelling. He has been with Tecnológico de Monterrey Campus Estado de México since 1999, and currently he is Head of the Communications Research group at Campus Estado de México. Dr José Antonio Delgado-Penin is a full professor at the Department of Signal Theory and Communications, at Universitat Politécnica de Catalunya, Spain since 1984. His Academic, technical and research activities have been at Philips N.V, ETSITM, Polito, CNET, Univ. Manchester and UCLA amongst others, all in the field of Telecommunications engineering.