High-altitude platforms for wireless communications

High-altitude platform stations offer a promising new technology that combines the benefits of terrestrial and satellite communication systems for delivering broadband communications to users at a low cost. They are easily deployable and easy to maintain, which is why they offer a good alternative for network operators who need to find ways to get more coverage to satisfy the increasing demand for more capacity. HAPS are usually balloons, airships or unmanned aerial systems (UAS) located in the stratosphere. An enormous interest has grown worldwide to examine their use not only for broadband communications, but also for emergency services, navigation, traffic monitoring, cellular, etc.

Key features include:

Unique book focusing on emerging HAPS technology and its applications Provides a thorough overview of the technology including HAPS-based communications systems, antennas for HAPS, radio propagation and channel modelling issues and HAPS networking aspects Presents various HAPS-related projects and initiatives developed throughout the world (North America, Europe and Asia-Pacific) Features a comprehensive overview on both aeronautical and telecommunications regulatory aspects, which will affect the deployment and future developments in the field of HAPS

High-Altitude Platform Systems for Wireless Communication s will prove essential reading for postgraduate students in the field of HAPS, engineers, developers and designers involved in the design and maintenance of HAPS, aerospace engineers, and communications system planners and researchers.

Author Notes

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.

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

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Table of Contents