Microwave Line of Sight Link Engineering

by Angueira, Pablo; Romo, Juan

• ISBN13: 9781118383421
• ISBN10: 1118383427
• Edition: 1st
• Format: eBook
• Copyright: 2012-08-07
• Publisher: Wiley

Summary

A comprehensive guide to the design, implementation, and operation of line of sight microwave link systems

The microwave Line of Sight (LOS) transport network of any cellular operator requires at least as much planning effort as the cellular infrastructure itself. The knowledge behind this design has been kept private by most companies and has not been easy to find. Microwave Line of Sight Link Engineering solves this dilemma. It provides the latest revisions to ITU reports and recommendations, which are not only key to successful design but have changed dramatically in recent years. These include the methodologies related to quality criteria, which the authors address and explain in depth.

Combining relevant theory with practical recommendations for such critical planning decisions as frequency band selection, radio channel arrangements, site selection, antenna installation, and equipment choice, this one-stop primer:

• Describes the procedure for designing a frequency plan and a channel arrangement structure according to ITU current standards, illustrated with specific application examples
• Offers analytical examples that illustrate the specifics of calculations and provide order of magnitude for parameters and design factors
• Presents case studies that describe real-life projects, putting together the puzzle pieces necessary when facing a real design created from scratch

Microwave Line of Sight Link Engineering is an indispensable resource for radio engineers who need to understand international standards associated with LOS microwave links. It is also extremely valuable for students approaching the topic for the first time.

Author Biography

PABLO ANGUEIRA, PhD, is an Associate Professor in the Department of Communication Engineering of the University of the Basque Country UPV/EHU. He has been involved in radio communications research and teaching activities for more than fifteen years. He is author of several contributions to the ITU-R WP3 and WP6 groups as well as many journal and international conference papers. He is Associate Editor of the IEEE Transactions on Broadcasting journal.

JUAN ANTONIO ROMO, PhD, is an Associate Professor teaching fixed, mobile, and satellite radio systems in the Department of Communication Engineering of the University of the Basque Country UPV/EHU. He has twenty-five years' experience in diverse areas of radio communications, in both manufacturing and network operations.

Table of Contents

PREFACE xix

ACRONYMS xxiii

1 INTRODUCTION TO MICROWAVE LOS LINK SYSTEMS 1

1.1 Introduction / 1

1.2 Historic Evolution of Radio Links / 3

1.3 Point-to-Point Fixed Communication Technologies / 5

1.3.1 Cabled Transport Systems / 6

1.3.1.1 xDSL Technologies / 6

1.3.1.2 Fiber-Optic Links / 8

1.3.2 Satellite Communication Links / 9

1.3.3 Other Fixed Wireless Systems / 11

1.3.3.1 Free Space Optic Links / 11

1.3.3.2 Wireless Point-to-Multipoint Systems / 12

1.3.3.3 High-Frequency Links / 13

1.3.3.4 High-Altitude Platform Stations (HAPS) / 13

1.4 Field of Application and Use Cases / 13

1.4.1 Backhaul Networks / 14

1.4.2 Backhaul in Mobile Networks / 14

1.4.3 Metro and Edge Networks / 16

1.4.4 Fixed Access Networks / 17

1.4.5 Additional Use Cases / 17

1.5 Basic Structure of a Fixed Service Microwave Link / 18

1.6 Spectrum Management Aspects / 21

1.6.1 ITU-R Radio Regulations: Spectrum Parameters and Definitions / 22

1.6.2 Frequency Allocations / 24

1.7 First Approach to the Design of a Microwave LOS Link / 26

1.8 Link Budget Basics / 28

1.8.1 Link Budget / 28

1.8.1.1 Power Levels / 29

1.8.1.2 Gain and Losses / 29

1.8.1.3 Link Budget Expression / 31

1.8.2 Propagation Losses / 31

1.8.3 Threshold Values and Gross Fade Margin / 33

1.9 Noise / 36

1.10 Interferences / 39

Bibliography / 40

2 LOSS AND FADING ASSOCIATED WITH TROPOSPHERE PROPAGATION PHENOMENA 42

2.1 Introduction / 42

2.2 Influence of Refraction on Propagation in the Troposphere / 43

2.2.1 Refractive Index and Radio Refractivity N / 46

2.2.2 Radio Refractivity Gradient / 47

2.2.2.1 Variation with Height / 47

2.2.3 Subrefraction Conditions / 48

2.2.4 Super-Refraction Conditions / 48

2.2.5 Ray Bending: Effective Earth Radius / 51

2.2.6 Ducts / 54

2.2.7 Beam Spreading / 56

2.2.8 Variation in the Angles of Launch and Arrival / 57

2.2.9 Troposphere Multipath Propagation / 57

2.2.10 Scintillation / 59

2.3 Terrain Diffraction Losses: Fresnel Zones / 59

2.4 Vegetation Attenuation / 60

2.5 Atmospheric Gas and Vapor Absorption / 61

2.6 Hydrometeors / 62

2.6.1 Absorption Due to Hydrometeors / 63

2.6.2 Cross-Polarization: Coupling Losses / 64

2.7 Reflection / 65

2.8 Distortion due to Propagation Effects / 67

2.8.1 Channel Impulse Response / 67

2.8.2 Two-Ray Model: Frequency Response / 68

Bibliography / 70

3 FREQUENCY PLAN FOR A FIXED SERVICE MICROWAVE LINK 72

3.1 Frequency Planning Overview / 72

3.2 Bandwidth and Capacity of a Microwave LOS Link / 74

3.2.1 Gross and Net Bit Rate / 75

3.2.2 Spectrum Efficiency / 76

3.2.3 Spectrum Resources / 77

3.3 ITU-R Frequency Plans / 79

3.3.1 General Description of a Radio-Frequency Channel Arrangement Plan / 83

3.3.2 Radio Channel Arrangement Options / 85

3.3.2.1 Alternated Radio Channel Arrangements / 85

3.3.2.2 Radio Channel Arrangements for Co-Channel Band Reuse / 86

3.3.2.3 Radio Channel Arrangements for Interleaved Band Reuse / 87

3.3.3 Radio-Frequency Channel Arrangement Plan: A Detailed Example / 88

3.3.3.1 40 MHz Alternated Radio Channel Arrangement / 88

3.3.3.2 20 MHz Alternated Radio Channel Arrangement / 90

3.3.3.3 30 MHz Radio Channel Arrangement / 91

3.3.3.4 10 MHz Radio Channel Arrangement / 92

3.3.3.5 5 MHz Radio Channel Arrangement / 92

3.3.3.6 Co-Polar Channel Arrangements with Multicarrier Transmission / 92

3.4 Assignment of Radio-frequency Channels / 93

3.4.1 Assignment of Half Bands to Stations / 93

3.4.1.1 Linear Topology / 93

3.4.1.2 Ring Topology / 94

3.4.2 Two Frequency Assignment Plan / 95

3.4.3 Assignment Plan Using More Than Two Frequencies / 97

3.5 Comments on the Frequency Band Choice / 97

Bibliography / 99

4 EQUIPMENT AND SUBSYSTEM TECHNOLOGY ASPECTS: A RADIO LINK DESIGNER APPROACH 100

4.1 Introduction / 100

4.2 Basic Block Diagrams / 102

4.2.1 Terminal Stations / 102

4.2.2 Repeater Stations / 105

4.3 Transport Technologies / 107

4.3.1 Plesiochronous Digital Hierarchy PDH / 108

4.3.2 SONET/SDH Synchronous Networks / 109

4.3.3 ATM Asynchronous Transfer Mode / 111

4.3.4 Ethernet / 112

4.3.5 Synchronization in Hybrid TDM/Ethernet Networks / 113

4.4 Baseband Unit / 114

4.4.1 Digital Interfaces / 115

4.4.2 TDM Radio / 116

4.4.2.1 Aggregated Radio Frame Structure / 117

4.4.2.2 Coding and Error Correction / 117

4.4.2.3 BaseBand Processing / 118

4.4.3 Ethernet Radio / 119

4.4.4 Hybrid Radio / 120

4.4.5 Channel Filtering / 121

4.5 Modulation and Demodulation / 123

4.5.1 Modulator and Demodulator Performance / 125

4.5.2 Examples of Modulation Schemes / 128

4.5.2.1 Phase Shift Keying 4-PSK / 128

4.5.2.2 16 Level Quadrature Amplitude Modulation (16-QAM) / 129

4.5.2.3 M level Quadrature Amplitude Modulation (M-QAM) / 130

4.5.2.4 Coded Modulation / 131

4.5.3 Adaptive Modulation / 132

4.5.4 Error Probability / 134

4.5.5 Adaptive Equalization / 137

4.5.5.1 Frequency Domain Equalization / 137

4.5.5.2 Time Domain Equalization / 138

4.5.6 Cross-Polar Interference Canceler / 138

4.6 Transceiver Unit / 139

4.6.1 Frequency Converter / 139

4.6.2 Transmitter Power Amplifier / 140

4.6.3 Receiver RF Low Noise Amplifier / 141

4.6.4 Receiver IF Amplifier / 141

4.6.5 Microwave Circuit Integration / 142

4.7 Antenna Coupling Elements / 142

4.7.1 RF Transmission Lines / 143

4.7.1.1 Coaxial Cables / 143

4.7.1.2 Wave Guides / 144

4.7.2 Branching Circuits / 145

4.7.2.1 Filters / 145

4.7.2.2 Circulators / 145

4.7.2.3 RF Isolators / 145

4.7.2.4 Duplexers / 146

4.7.3 Transmission Line Selection Criteria / 146

4.8 Antennas / 147

4.8.1 Parameters of Parabolic Reflectors / 148

4.8.2 Antenna Gain / 149

4.8.2.1 Directivity / 149

4.8.2.2 Gain / 150

4.8.2.3 Aperture Efficiency / 150

4.8.2.4 Equivalent Isotropically Radiated Power (E.I.R.P) / 151

4.8.3 Radiation Pattern / 152

4.8.3.1 Beamwidth / 156

4.8.3.2 Minor or Secondary Lobes / 157

4.8.3.3 Field Regions / 157

4.8.4 Mismatch, VSWR and Returning Losses / 157

4.8.5 Polarization / 159

4.8.6 Parabolic Antenna Types / 161

4.8.6.1 Grid Antennas / 161

4.8.6.2 Standard Antennas / 161

4.8.6.3 Focal Plane Antenna / 161

4.8.6.4 Shielded Antenna / 162

4.8.6.5 High Performance Antennas / 162

4.8.7 Microwave Antenna Selection Criteria / 163

4.8.7.1 Operating Frequency Band and Size / 163

4.8.7.2 Gain / 163

4.8.7.3 Radiation Patterns / 163

4.8.7.4 Polarization / 164

4.8.7.5 VSWR / 164

4.8.7.6 Tower Loading and Environmental Considerations / 165

4.9 Redundancy Arrangements / 166

4.9.1 Unprotected Configurations / 168

4.9.2 Hot Standby Configuration / 168

4.9.3 Frequency Diversity Configuration / 169

4.9.4 2 + 0 Protection with Radio-Link Bonding / 169

4.9.5 MIMO Configurations / 170

4.10 System Monitoring and Management / 171

Bibliography / 172

5 PERFORMANCE OBJECTIVES AND CRITERIA FOR FIXED SERVICE MICROWAVE LINKS 174

5.1 Introduction / 174

5.2 Error Performance Objectives and Criteria Based on Recommendation ITU-T G.821 / 176

5.2.1 Application Scope of Related Recommendations / 176

5.2.2 Error Performance and Associated Definitions / 176

5.2.2.1 Error Performance Events / 176

5.2.2.2 Error Performance Parameters / 177

5.2.3 Reference Transmission Models for Performance Objective Allocation / 178

5.2.4 Objectives and End-to-End Error Performance Allocation in Real Links / 178

5.3 Error Performance Objectives and Criteria Based on Recommendations ITU-T G.826 and ITU-T G.828 / 179

5.3.1 Application Scope / 179

5.3.2 Error Performance and Associated Definitions / 180

5.3.2.1 Error Performance Events for Connections (HRX Model) / 181

5.3.2.2 Error Performance Events for Paths (HRDP Model) / 182

5.3.2.3 Error Performance Parameters / 182

5.3.3 Reference Transmission Models for Performance Objective Allocation / 182

5.3.4 Objectives and End-to-End Error Performance Allocations in Real Links / 184

5.3.4.1 Links in the International Portion / 186

5.3.4.2 Links in the National Portion / 187

5.4 Availability Criteria / 188

5.4.1 Availability Criteria for Unidirectional Systems / 188

5.4.2 Criteria for Bidirectional Paths/Connections / 188

5.4.3 Availability Parameters / 189

5.5 Availability Objectives for Microwave LOS Links Designed Before 2005 / 190

5.5.1 Basic Concepts and Definitions / 190

5.5.2 Availability Objectives in Real Links / 191

5.6 Availability Objectives for Microwave LOS Links Designed After 2005 / 192

5.6.1 Recommendations and Application Scope / 192

5.6.2 Reference Models for Availability Objective Allocation / 192

5.6.3 Error Performance Concepts Related to Availability / 193

5.6.4 Availability Objectives in Real Microwave LOS Links / 193

5.7 ITU Error Performance and Availability Usage Guidelines / 194

5.8 Degradation due to Interferences / 195

Bibliography / 196

Appendix I: Tables for Error Performance Objective Calculations.

Recommendation ITU-R F.1668 / 198

Appendix II: Tables for Availability Objective Calculations.

Recommendation ITU-R F.1703 / 201

Appendix III: Case Studies for Error Performance Objective Calculations. Recommendation ITU-R F.1668 / 202

Appendix IV: Case Studies for Availability Objective Calculations.

Recommendation ITU-R F.1703 / 204

6 LINK PATH ENGINEERING 207

6.1 General Considerations on Link Path Engineering / 207

6.2 Site Selection Criteria / 209

6.3 Digital Terrain Databases / 211

6.4 Profile Extraction, Clearance, and Obstructions / 212

6.5 Optimum Choice of Antenna Heights / 216

6.5.1 Obstacle Clearance Objectives and Criteria / 217

6.5.1.1 Non-diversity Antenna Configurations / 218

6.5.1.2 Two and Three Antenna Space Diversity Configurations / 219

6.5.2 Relevant Reflection Reduction Procedures for Non-diversity Configurations / 221

6.5.2.1 Areas Causing Relevant Reflection / 221

6.5.2.2 Shielding of the Reflection Point / 221

6.5.2.3 Translating the Reflection Point / 222

6.5.3 Calculation of Potential Reflection Areas / 222

6.5.3.1 Geometrical Method / 222

6.5.3.2 Analytic Method / 223

Bibliography / 226

7 PROPAGATION CALCULATION METHODS ACCORDING TO ITU-R P SERIES RECOMMENDATIONS 227

7.1 General Considerations on Propagation Calculation Methods / 227

7.2 Fading Definition / 228

7.3 Reflection on Earth’s Surface / 230

7.3.1 Effective Surface Reflection Coefficient / 230

7.3.2 Fading Associated with Specular Reflections / 234

7.4 Attenuation Due to Atmospheric Gases / 236

7.5 Diffraction Fading / 237

7.5.1 Simplified Calculation from ITU-R Recommendation P.530 / 238

7.5.2 Diffraction on a Knife-Edge / 239

7.5.3 Single Round Shaped Obstacle / 240

7.5.4 Two Isolated Obstacles / 242

7.5.4.1 Two Obstacles with Similar Clearance / 243

7.5.4.2 Two Obstacles with Different Clearance / 243

7.5.5 Multiple Isolated Obstacles / 245

7.6 Multipath Flat Fading / 245

7.6.1 Prediction for Small Percentages of Time / 246

7.6.1.1 Initial Planning Stage / 246

7.6.1.2 Detailed Planning Stage / 247

7.6.2 Prediction for All Percentages of Time / 248

7.7 Distortion Due to Multipath Propagation Effects Under Clear Sky / 250

7.7.1 Signature / 251

7.7.2 Outage Probability Calculation Based on Signatures / 253

7.8 Attenuation due to Hydrometeors / 255

7.8.1 Prediction of Attenuation Due to Rain / 255

7.8.1.1 Specific Attenuation Calculation / 256

7.8.1.2 Method for Rain Intensity Excess Value for a Certain Probability Target / 257

7.8.2 Combined Method for Rain and Wet Snow / 258

7.8.3 Frequency Extrapolation / 260

7.8.4 Polarization Extrapolation / 260

7.8.5 Attenuation Due to Clouds and Fog / 260

7.9 Reduction of Cross-Polar Discrimination (XPD) / 262

7.9.1 XPD Outage Under Clear-Air Conditions / 262

7.9.2 XPD Outage Caused by Rain / 264

7.10 ITU-R Databases for Tropospheric Propagation Studies / 265

Bibliography / 266

Appendix I: Data for Specific Attenuation Calculation γ R / 266

Appendix II: Data for Calculating Attenuation Due to Wet Snow / 270

8 LINK ENGINEERING ACCORDING TO AVAILABILITY AND ERROR PERFORMANCE CRITERIA 271

8.1 Introduction / 271

8.2 Design According to Availability and Error Performance / 272

8.2.1 Initial Specifications / 272

8.2.2 Microwave LOS Link Design Diagram / 273

8.2.3 Error Performance and Availability Objectives / 274

8.2.3.1 Availability and Bit Error Rate / 274

8.2.3.2 Error Performance Criteria and Bit Error Rate / 275

8.2.4 Link Budget and Thresholds / 276

8.2.5 Impact of Propagation on Availability and Error Performance Calculations / 278

8.3 Microwave LOS Link Design According to Availability Criteria / 281

8.3.1 General / 281

8.3.2 Unavailability Caused by Rain / 282

8.3.3 Rain Attenuation in Multiple Hop Links / 283

8.3.4 Equipment Reliability and Unavailability / 284

8.4 Microwave LOS Link Design According to Error Performance Objectives / 285

8.4.1 General / 285

8.4.2 Design for Operation in Flat Fading Conditions / 286

8.4.2.1 Error Performance and Flat Fading Caused by Refraction / 287

8.4.2.2 Error Performance and Rain / 289

8.4.3 Error Performance and Selective Fading Due to Multipath / 290

8.4.3.1 Net-Fade Margin Method / 291

8.4.4 Occurrence of Simultaneous Fading on Multihop Links / 292

8.4.5 Cross-Polar Discrimination (XPD) Reduction Outages / 293

8.4.6 Overall Error Performance / 293

8.5 Design in Problematic Propagation Environments / 294

8.5.1 Diversity Techniques / 294

8.5.1.1 Space Diversity / 295

8.5.1.2 Angle Diversity / 297

8.5.1.3 Frequency Diversity / 299

8.5.1.4 Combined Diversity: Space and Frequency / 301

8.5.2 Adaptive Channel Equalization / 303

8.5.3 Adaptive Equalization Combined with Spatial Diversity / 303

8.5.4 Considerations on System Design in the Presence of Ducts / 304

8.6 Quality and Availability Calculation Guidelines in Real Links / 304

8.6.1 Availability / 304

8.6.2 Error Performance / 305

8.7 Interferences / 306

8.7.1 Interferences in the Link Design Process / 306

8.7.2 Reference C/I Values and Threshold Degradation / 308

8.7.3 Interference Propagation / 308

8.7.4 Carrier to Interference (C/I) Calculation Model / 309

8.7.4.1 Multiple Interferences / 312

8.7.4.2 Common Interference Situations / 312

8.7.5 Interference Calculations in Dense Frequency Reuse Scenarios / 315

8.8 Link Engineering Summary Procedure / 319

Bibliography / 319

9 LINK OPERATION AND MONITORING 321

9.1 Introduction / 321

9.2 Reference Performance Objectives (RPO) / 322

9.3 Bringing into Service (BIS) / 325

9.3.1 BIS Performance Objective Values Calculation Procedure / 325

9.3.2 BIS Test and Evaluation Procedure / 325

9.4 Maintenance / 328

9.4.1 Calculation Method for Maintenance Performance Limits (MPL) / 329

9.4.2 Maintenance Procedures / 330

9.4.2.1 T1 Threshold Supervision / 330

9.4.2.2 T2 Threshold Supervision / 331

9.4.2.3 T3 Threshold Supervision / 331

9.4.2.4 Long-Term Measurement and Monitoring / 331

9.4.3 Availability / 331

9.4.4 Evaluation of Error Performance Parameters / 332

9.4.5 Fault Location Procedures / 332

9.4.5.1 Fault Location in pre-ISM Environments / 332

9.4.5.2 Fault Location in ISM Environments / 333

Bibliography / 333

APPENDIX 335

INDEX 378