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Implementation of a 3D Terrain-Dependent Wave Propagation Model in WRAP

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Implementation of a 3D Terrain-Dependent Wave Propagation Model in WRAP Linnӕus University Department of Physics and Electrical Engineering Master’s thesis in Electrical Engineering, with specialization in Signal Processing and Wave Propagation Implementation of a 3D terrain-dependent Wave Propagation Model in WRAP Author(s): Gent Gashi, Valon Blakaj Supervisor(s): Olov Carlsson, Anders Thomasson Examiner: Sven-Erik Sandström Date: 2014.09.04 Course Code: 5ED06E Subject: Wave Propagation Level: Advanced ‘Wireless is all very well but I’d rather send a message by a boy on a pony’! Lord Kelvin Acknowledgements This project wouldn’t be possible without cooperation between Linnaeus University and WRAP International AB; therefore, we would like to express our sincerest gratitude to our supervisors at WRAP Olov Carlsson and Anders Thomasson for their patience, motivation and for invaluably useful practical advices. We are thankful to Lantmäteriet (The Swedish mapping, cadastral and land registration authority) for providing the detailed geo-data over central Stockholm; and AerotechTelub, FOI (the Swedish Defence Research Agency), FMV (the Swedish Defence Materiel Administration) for the measured signal level data. We would like to thank the Linnaeus-Palme exchange program for providing us the opportunity to complete the second year of Master’s studies in Sweden, and especially Prof. Arianit Kurti who was the coordinator of this exchange program. We are grateful to the Linnaeus University staff, especially to Prof. Sven-Erik Sandström for guiding us throughout this year of studies in Sweden. Special thanks go to our professor in University of Prishtina, Prof. Driton Statovci for his continuous guidance during our Master’s studies, and in general to the staff of the University of Prishtina. Last but not least, we want to thank our families and friends for their moral support and words of encouragement. iii Abstract The radio wave propagation prediction is one of the key elements for designing an efficient radio network system. WRAP International has developed a software for spectrum management and radio network planning. This software includes some wave propagation models which are used to predict path loss. Current propagation models in WRAP perform the calculation in a vertical 2D plane, the plane between the transmitter and the receiver. The goal of this thesis is to investigate and implement a 3D wave propagation model, in a way that reflections and diffractions from the sides are taken into account. The implemented 3D wave propagation model should be both fast and accurate. A full 3D model which uses high resolution geographical data may be accurate, but it is inefficient in terms of memory usage and computational time. Based on the fact that in urban areas the strongest path between the receiver and the transmitter exists with no joint between vertical and horizontal diffractions [10], the radio wave propagation can be divided into two parts, the vertical and horizontal part. Calculations along the horizontal and vertical parts are performed independently, and after that, the results are combined. This approach leads to less computational complexity, faster calculation time, less memory usage, and still maintaining a good accuracy. The proposed model is implemented in C++ and speeded up using parallel programming techniques. Using the provided Stockholm high resolution geographical data, simulations are performed and results are compared with real measurements and other wave propagation models. In addition to the path loss calculation, the proposed model can also be used to estimate the channel power delay profile and the delay spread. Key words: radio wave propagation, WRAP International, C++, geographical data, reflection, diffraction, path loss, power delay profile, delay spread iv Contents Abstract ....................................................................................................................................................... iv List of figures ............................................................................................................................................. vii List of tables................................................................................................................................................ ix Chapter 1: Radio wave propagation ........................................................................................................ 1 1.1 Introduction to Radio Waves .............................................................................................................. 1 1.2 The Wireless Channel ......................................................................................................................... 2 1.3 Propagation Phenomena ...................................................................................................................... 3 1.3.1 Free Space Path Loss ................................................................................................................... 3 1.3.2 Reflection ..................................................................................................................................... 4 1.3.3 Scattering ..................................................................................................................................... 5 1.3.4 Diffraction .................................................................................................................................... 5 1.4 The Fresnel Zone ................................................................................................................................ 6 1.5 Knife-Edge Diffraction Methods ........................................................................................................ 7 1.5.1 Single-Edge Diffraction ............................................................................................................... 8 1.5.2 The Bullington Method ................................................................................................................ 9 1.5.3 The Epstein-Peterson Method ...................................................................................................... 9 1.5.4 The Deygout Method ................................................................................................................. 10 1.5.5 The Giovaneli Method ............................................................................................................... 11 1.5.6 The Vogler Method .................................................................................................................... 12 1.5.7 Comparison between multiple knife-edge diffraction methods ................................................. 13 1.6 Attenuation due to Vegetation .......................................................................................................... 14 Chapter 2: The WRAP 3D Wave Propagation Model ........................................................................... 16 2.1 Introduction to outdoor wave propagation models ........................................................................... 16 2.1.1 Log-distance path loss model ..................................................................................................... 16 2.1.2 COST 231 Walfisch-Ikegami ..................................................................................................... 17 2.1.3 Ray tracing and ray launching ................................................................................................... 18 2.1.4 Finite difference time domain (FDTD) ...................................................................................... 19 2.2 Overview of WRAP 3D .................................................................................................................... 19 2.3 The Horizontal Part ........................................................................................................................... 19 2.3.1 Environmental Information ........................................................................................................ 20 2.3.2 Discrete Ray Launching ............................................................................................................. 22 v 2.3.3 Horizontal reflections and diffractions....................................................................................... 27 2.3.4 Angular Dispersion .................................................................................................................... 27 2.3.6 Modelling of Radio Wave Propagation in Horizontal Part ........................................................ 28 2.4 Vertical Part ...................................................................................................................................... 29 2.5 Combining Vertical and Horizontal parts ......................................................................................... 31 2.6 Power Delay Profile and RMS Delay Spread ................................................................................... 31 Chapter 3: Results ..................................................................................................................................... 34 3.1 Introduction ....................................................................................................................................... 34 3.2 Averaging Interval – Lee Method ..................................................................................................... 34 3.3 Accuracy testing methods ................................................................................................................
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