OPTIMIZATION OF AN SDR BASED AERIAL BASE STATION Steffy Ann Mathews Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS August 2017 APPROVED: Kamesh Namuduri, Major Professor Murali Varanasi, Committee Member Mark Thompson, Committee Member Shengli Fu, Chair of the Department of Electrical Engineering Costas Tsatsoulis, Dean of the College of Engineering Victor Prybutok, Dean of the Toulouse Graduate School Mathews, Steffy Ann. Optimization of an SDR Based Aerial Base Station. Master of Science (Electrical Engineering), August 2017, 74 pp., 7 tables, 29 figures, 31 numbered references. This thesis proposes a design of a rapidly deployable GSM base station that provides voice and data communication and it is interoperable with the existing network infrastructure. The prototype is based on software defined radios and makes use of IEEE 802.11 unlicensed wireless Radio Frequency band for backhaul link and an open source GSM implementation software. The prototype is evaluated in line-of-sight and non-line-of-sight environments to measure the quality of the received signal strength and coverage area. The setup is then optimized to increase the quality of service. It is observed that in environments with limited obstacles the base station covers a larger area with good quality of service. On the other hand, when the environments are filled with obstacles the coverage area decreases along with the quality of service due to interference and fading. It is concluded that in order to achieve strong received signals and larger coverage area the transmit power needs to be increased. Copyright 2017 By Steffy Ann Mathews ii ACKNOWLEDGEMENTS Foremost, I would like to express my sincere gratitude to my advisor Dr. Kamesh Namuduri for the continuous support of my Master’s study and research, for his patience, motivation, enthusiasm, and immense knowledge. His guidance and unwavering enthusiasm for emergency communications helped me in all the time of my research. I am extremely thankful to my colleagues and friends Ramanpreet Singh and Oghenetega Agbogidi for their valuable guidance and support for completion of this project. My appreciation also extends to Kunal Bhadane, Samuel Iyiola, Nabila Salma and Roya Nourouzi for their encouragement, support and advice. I also acknowledge Peggy Foster and Richard for their help and cooperation in completing my thesis. Last but not the least, my gratitude goes to my family for their undying love and support - my parents, Mr and Mrs. Mathew Varghese. This would not have been possible without their guidance and strength. iii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ................................................................................................................... iii LIST OF TABLES .............................................................................................................................. viii LIST OF FIGURES .............................................................................................................................. ix CHAPTER 1. INTRODUCTION ........................................................................................................... 1 1.1. Background ............................................................................................................. 1 1.2. Motivation ............................................................................................................... 2 1.3. Objective ................................................................................................................. 3 1.4. Overview ................................................................................................................. 3 CHAPTER 2. LITERATURE REVIEW ................................................................................................... 4 2.1. Propagation Models ................................................................................................ 4 2.1.1. Propagation Method for RF Signals in an Urban Environment .................. 4 2.1.2. Propagation Modeling for Air-to Ground Radio Channels in Urban Environment................................................................................................ 5 2.1.3. Adaptation of Signal Propagation Model By means of an Airborne GSM Base Station ................................................................................................ 5 2.1.4. Evaluation of Models .................................................................................. 6 2.2. Path Loss ................................................................................................................. 6 2.2.1. Path Loss Exponent ..................................................................................... 7 2.2.2. Free-Space Path Loss .................................................................................. 8 2.2.3. Modelling of Mean Path Loss ..................................................................... 9 2.2.4. OLoS and NLoS Path Loss Modelling ........................................................... 9 2.3. Optimum Altitude of a LAP ................................................................................... 10 2.4. Impact of Altitude and Other Related Factors on Coverage Probability .............. 11 2.5. Optimal UAV Altitude ........................................................................................... 12 2.6. Optimal Position ................................................................................................... 12 2.7. Coverage of the LAP .............................................................................................. 13 2.8. Coverage Probability ............................................................................................. 13 iv 2.9. D2D and DU Coverage Probability as a Function of the UAV Altitude ................. 14 2.10. Propagation Path Visibility .................................................................................... 14 2.10.1. Estimation of Visibility .............................................................................. 14 2.10.2. Verification of Visibility Estimation Method ............................................. 15 2.11. Probability of Collision .......................................................................................... 15 2.12. Performance and Trade-offs of UAVs ................................................................... 15 2.13. Building Blockage .................................................................................................. 16 2.14. Distortion in Propagation Channel ....................................................................... 16 2.15. Multi Path Reflections ........................................................................................... 17 2.16. Interference .......................................................................................................... 17 CHAPTER 3. EMERGENCY COMMUNICATION SYSTEMS ............................................................... 19 3.1. Emergency Communication Systems .................................................................... 19 3.2. Challenges of Emergency Communication Systems ............................................. 20 3.3. GSM ....................................................................................................................... 22 3.4. Base Station .......................................................................................................... 23 3.5. Components of an Aerial Base Station ................................................................. 25 3.5.1. Software Defined Radio ............................................................................ 25 3.5.2. BladeRF ..................................................................................................... 26 3.5.3. Raspberry pi .............................................................................................. 27 3.5.4. Yate BTS .................................................................................................... 29 3.5.5. Antenna ..................................................................................................... 30 3.6. Channel Model ...................................................................................................... 32 3.6.1. COST 231 Model- Extension to Hata Model ............................................. 33 3.6.2. COST 231 Walfisch-Ikegami Model ........................................................... 34 3.7. Signal Booster ....................................................................................................... 37 CHAPTER 4. DESIGN AND EVALUATION ........................................................................................ 38 4.1. Base Stations for Emergency and Temporary Events ........................................... 38 4.2. Research Methodology ......................................................................................... 40 4.3. Setup of an SDR Based Deployable GSM Base Station ......................................... 41 4.4. Experiment ............................................................................................................ 43 v 4.4.1. Measurement............................................................................................ 43 4.4.2. Mathematical Formulation for Coverage Area ......................................... 43 4.5. Optimization ........................................................................................................