The Impact of Rayleigh Fading Channel Effects on the RF-DNA
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THE IMPACT OF RAYLEIGH FADING CHANNEL EFFECTS ON THE RF-DNA FINGERPRINTING PROCESS By Mohamed Fadul Donald R. Reising Abdul R. Ofoli Assistant Professor UC Foundation Associate Professor (Committee Chair) (Committee Member) Thomas D. Loveless UC Foundation Assistant Professor (Committee Member) THE IMPACT OF RAYLEIGH FADING CHANNEL EFFECTS ON THE RF-DNA FINGERPRINTING PROCESS By Mohamed Fadul A Thesis Submitted to the Faculty of the University of Tennessee at Chattanooga in Partial Fulfillment of the Requirements of the Degree of Master of Science: Engineering The University of Tennessee at Chattanooga Chattanooga, Tennessee August 2018 ii ABSTRACT The Internet of Things (IoT) consists of many electronic and electromechanical devices connected to the Internet. It is estimated that the number of IoT-connected devices will be between 20 and 50 billion by the year 2020. The need for mechanisms to secure IoT networks will increase dramatically as 70% of the edge devices have no encryption. Previous research has proposed RF- DNA fingerprinting to provide wireless network access security through the exploitation of PHY layer features. RF-DNA fingerprinting takes advantage of unique and distinct characteristics that unintentionally occur within a given radio’s transmit chain during waveform generation. In this work, the application of RF-DNA fingerprinting is extended by developing a Nelder-Mead-based algorithm that estimates the coefficients of an indoor Rayleigh fading channel. The performance of the Nelder-Mead estimator is compared to the Least Square estimator and is assessed with degrading signal-to-noise ratio. The Rayleigh channel coefficients set estimated by the Nelder- Mead estimator is used to remove the multipath channel effects from the radio signal. The resulting channel-compensated signal is the region where the RF-DNA fingerprints are generated and classified. For a signal-to-noise ratio greater than 21 decibels, an average percent correct classification of more than 95% was achieved in a two-reflector channel. iii ACKNOWLEDGEMENTS First, I would like to express my sincere gratitude to my advisor, Dr. Reising, for the continuous support of my thesis study and related research, and for his patience, motivation, and immense knowledge. His guidance helped me over the whole course of the research and writing for this thesis. Besides my advisor, I would like to also thank the rest of my thesis committee: Dr. Loveless, and Dr. Ofoli, for their insightful comments and encouragement. I would also like to thank the Department of Electrical Engineering of The University of Tennessee at Chattanooga for all its support and the great professors it provided. iv TABLE OF CONTENTS ABSTRACT ....………………………………………………………………..……………….... iii ACKNOWLEDGEMENTS …………………………………………………………..………….iv LIST OF TABLES ………………………………………………………………………………vii LIST OF FIGURES …………………………………………………………….....……………viii LIST OF ABBREVIATIONS…………………………..……..………………………..…………x CHAPTER 1. INTRODUCTION ........................................................................................................... 1 Overview .......................................................................................................................... 1 Motivation ........................................................................................................................ 2 Problem Statement ........................................................................................................... 3 Objectives ........................................................................................................................ 5 Research Contributions .................................................................................................... 5 Thesis Outlines................................................................................................................. 7 2. BACKGROUND ............................................................................................................. 8 Signal of Interest .............................................................................................................. 8 Channel Modeling .......................................................................................................... 11 Overview ............................................................................................................... 11 Indoor Multipath Channel Modeling .................................................................... 13 Rayleigh Channel Model ...................................................................................... 13 Time Offset Estimation .................................................................................................. 16 Carrier Frequency Offset Estimation ............................................................................. 18 Channel Estimation and Equalization ............................................................................ 21 Least Square Estimator ......................................................................................... 22 Nelder-Mead Estimator ......................................................................................... 23 RF-DNA Fingerprinting................................................................................................. 26 Device Classification ..................................................................................................... 28 v Relevant Work ............................................................................................................... 31 Joint Channel Estimation and Classification ........................................................ 31 Nonlinearity Estimation for Specific Emitter Identification ................................. 33 3. METHODOLOGY ........................................................................................................ 35 Introduction .................................................................................................................... 35 Signal Detection and Collection .................................................................................... 36 Noisy Multipath Signal Generation ............................................................................... 38 Time Synchronization .................................................................................................... 40 Least Square Estimator .................................................................................................. 43 Nelder-Mead Estimator .................................................................................................. 46 Channel Equalization ..................................................................................................... 48 RF-DNA Fingerprint Generation ................................................................................... 49 Device Classification ..................................................................................................... 50 4. RESULTS AND DISCUSSION .................................................................................... 51 LS and N-M Estimator ................................................................................................... 52 Device Classification ..................................................................................................... 53 Two-Reflector Channel .......................................................................................... 55 Five-Reflector Channel .......................................................................................... 56 5. CONCLUSION .............................................................................................................. 60 Future Work ................................................................................................................... 61 REFERENCES..…………………………………………………………………………………64 VITA .……………………………………………………………………………………………68 vi LIST OF TABLES 4.1 Reflector Parameters for L = 2 Rayleigh Channel………………………………….52 4.2 Reflector Parameters for L = 5 Rayleigh Channel ………………………………....57 vii LIST OF FIGURES Figure 1.1 Open Systems Interconnect (OSI) network model ........................................................ 3 Figure 2.2 Preamble structure ....................................................................................................... 11 Figure 2.3 Multipath propagation scenario with a line-of-sight component and three multipath components ................................................................................................................. 12 Figure 2.4 TDL representation of the Multipath channel ............................................................. 14 Figure 2.5 True time offset and beginning of the 802.11a payload .............................................. 18 Figure 2.6 Estimated time offset is earlier than the true time ....................................................... 19 Figure 2.7 Estimated time offset is later than the true time .......................................................... 20 Figure 2.8 Representation of a 2-D response generated using Gabor transform and normalized magnitude-squared GT coefficients ............................................................................ 28 Figure 2.9 MDA projection of fingerprints from NC = 3 class space to 2-D subspaces .............. 30 Figure 2.10 MDA/ML classification subspace for NC = 3; multivariate Gaussian distributions fited to projected fingerprints; ML decision boundaries............................................