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Coexistence of Wireless Systems for Spectrum Sharing

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Coexistence of Wireless Systems for Spectrum Sharing Coexistence of Wireless Systems for Spectrum Sharing Seungmo Kim Dissertation submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering Carl B. Dietrich, Chair Alan T. Asbeck Richard M. Buehrer Jeffrey H. Reed Yaling Yang June 7, 2017 Blacksburg, Virginia Keywords: Coexistence, Spectrum Sharing, mmW, 28 GHz, 70 GHz, 5G, Fixed Satellite Service, Fixed Service, 3.5 GHz, Pulsed Radar, OFDM, LTE, Wi-Fi, 5.9 GHz, DSRC, IEEE 802.11ac Copyright 2017, Seungmo Kim Coexistence of Wireless Systems for Spectrum Sharing Seungmo Kim (ABSTRACT) Sharing radio frequency (RF) spectrum among multiple wireless systems has emerged as a viable solution for alleviating the severe capacity crunch in next-generation wireless mobile networks such as 5th generation mobile networks (5G). Spectrum sharing can be achieved by enabling multiple wireless systems to coexist in a single spectrum band, via various means including signal processing, Medium Access Control (MAC), spatial multiple access techniques, etc. If successfully delivered, spectrum sharing therefore has the potential to significantly leverage spectral efficiency. In this dissertation, we discuss coexistence problems in spectrum bands that have recently been raising notable research interest, namely 27.5- 28.35 GHz (28 GHz), 71-76 GHz (70 GHz), 5.85-5.925 GHz (5.9 GHz), and 3.55-3.7 GHz (3.5 GHz) bands. We furnish a solution for coexistence at each of the spectrum bands after identifying unique characteristics of the spectrum sharing problem in each band. First, we characterize coexistence of 5G in the millimeter wave (mmW) bands{28 and 70 GHz. The incumbent systems with which 5G is to share the bands are Fixed Satellite Service and Fixed Service have been operating at 28 and 70 GHz, respectively. In the 28 GHz band, the uplink{Earth Station (ES) to space station (SS){of Fixed Satellite Service (FSS) operates, wherein two directions of interference should be analyzed: ES-to-5G interference and 5G-to-SS interference. In 70 GHz band, the most popular application of FS is wireless backhaul (WB) that connects cell towers in cellular communications systems. Coexistence with 5G is more sophisticated in this band due to bi-directional operation of WB, contrast to only upward transmission of FSS at 28 GHz. For each of the bands, we (i) model interferences between 5G and the incumbent systems, and (ii) propose methods for mitigating inter-system interference for each of the spectrum sharing scenarios. Second, coexistence of wireless communications system and pulsed radar at 3.5 GHz is discussed. In April 2015, the United States Federal Communications Commission (FCC) decided to open the band, which has mainly been utilized by military and meteorological radar, for shared usage with mobile broadband communications services. This dissertation answers the following questions regarding the coexisting systems: 1. How can a wireless communications system achieve acceptable performances under interference from coexisting radars? 2. How can a wireless communications system achieve maximum performances without causing harmful interference into coexisting radars? An answer to the first question is provided by suggesting an Orthogonal Frequency Division Multiplexing (OFDM) scheme that is robust against pulsed interference generated by coex- isting radars. The second question is addressed by (i) proposing a scheme for suppressing interference into a radar and (ii) measuring the level of performance degradation that a communications system experiences with application of the proposed scheme. Third, we study spectrum sharing between Dedicated Short-Range Communications (DSRC) and Wi-Fi in the 5.9 GHz band. The band has been reserved for intelligent transportation systems (ITS) since the FCC allocated the 75-MHz spectrum in October 1999. However, a bill called the Wi-Fi Innovation Act is introduced in the United States House of Represen- tatives in February 2015, to urge the FCC to explore the feasibility of opening up spectrum for unlicensed Wi-Fi use. One serious concern is that DSRC is applied for safety-critical applications such as collision warning that are designed to improve road safety. This raises higher necessity of thorough characterization of DSRC functions for safety-critical applica- tions in order to ensure that potential coexistence with Wi-Fi does not harm safety. To this end, a new performance metric that can better capture safety-critical operations of a DSRC network is proposed. Further, the new metric is then applied to characterize DSRC-Wi-Fi coexistence and to suggest proper operation parameters. The results presented in each of the aforementioned parts show comprehensively that the coexistence methods help achieve spectrum sharing in each of the bands, and therefore potentially contribute to increase of bandwidth efficiency. As spectrum sharing is proposed and implemented in more bands in the future, the techniques proposed and studied in this dissertation will provide examples of ways to achieve a viable solution for the ever evolving capacity demands in the wireless communications landscape. iii Coexistence of Wireless Systems for Spectrum Sharing Seungmo Kim (GENERAL AUDIENCE ABSTRACT) Sharing a band of frequencies in the radio spectrum among multiple wireless systems has emerged as a viable solution for alleviating the severe capacity crunch in next-generation wireless mobile networks such as 5th generation mobile networks (5G). Spectrum sharing can be achieved by enabling multiple wireless systems to coexist in a single spectrum band. In this dissertation, we discuss the following coexistence problems in spectrum bands that have recently been raising notable research interest: 5G and Fixed Satellite Service (FSS) at 27.5-28.35 GHz (28 GHz); 5G and Fixed Service (FS) at 71-76 GHz (70 GHz); vehicular com- munications and Wi-Fi at 5.85-5.925 GHz (5.9 GHz); and mobile broadband communications and radar at 3.55-3.7 GHz (3.5 GHz). The results presented in each of the aforementioned parts show comprehensively that the coexistence methods help achieve spectrum sharing in each of the bands, and therefore contribute to achieve appreciable increase of bandwidth efficiency. The proposed techniques can contribute to making spectrum sharing a viable solution for the ever evolving capacity demands in the wireless communications landscape. Dedication To my family... parents, sister, fiancee, for their unconditional support and love. v Acknowledgments I would like to begin this dissertation by thanking my dear family{my parents, sister Sohee Kim, and fiancee Jiwon Kim. Without their unconditional love and support, any of what I have got now would not have been possible. This achievement is as much their contribution as is mine for the very reason that they have always heartedly supported every decision I have made in my whole life. This bliss is for you all. Throughout my Ph.D. study, I have had one great fortune to work with a great advisor, Dr. Carl Dietrich. I appreciate your advice not only in my Ph.D. study but in many other aspects of life. I am privileged to have been one of his first doctoral students and thus am grateful for the passionate guidance. The time spent with him has better prepared me for the new chapter of my life at Georgia Southern University after this graduation. I hope that I can pay back to him via further academic collaborations. I also want to express a huge appreciation to the professors who served in my dissertation committee. I thank Dr. Jeff Reed for his interest in my work and for compassionate invita- tions to his Thanksgiving parties when we were the only souls left in town for the holidays every year. An as large appreciation must go to Dr. Michael Buehrer for his thorough re- view on my research. The advices and questions that he made in my Preliminary and Final Exams aided improve the quality and balance the perpective of this dissertation. To Dr. Yaling Yang, I appreciate her kind advice and conversations. Dr. Alan Asbeck well deserves a gratitude for bringing his solid understanding and creative perspectives into my research. Dr. Jung-min Park helped me start my Ph.D. work. I appreciate his advice and support in first three years. Many parts of enthusiasm toward research have been learned from him. I would like to thank Bob Lineberry and Jason Thweatt for the valuable pieces of advice that they have given to me. The time working with them as a graduate teaching assistant proved my eligibility in communicating with young students and brought me an opportunity to start my career as an educator, which I am grateful. I appreciate you two for such a great occasion and your favorable witness on what I have done with you in the reference letters to the university that hired me. The most fruitful and rewarding time that I remember looking back the entire Ph.D. period is the one with Nokia Bell Labs in the summer of 2016. I wish please Eugene Visotsky vi accepts my deepest appreciation for his passionate mentoring. To Prakash Moorut, I thank his endeavor of bringing out the results that we produced to the FCC and thus making them more visible. I thank Amitava Ghosh for granting me such a great opportunity to work with you smart (and handsome) researchers and keeping me motivated throughout. To Mark Cudak, I do not know if you would know that you were the person that I met on my first and last moments in the office. To Kamil Bechta, let me remember him for his hard work and co-authorship in our paper. I can never doubt that the earlier learnings formed a basis for my starting a Ph.D. study. There were great educators who inspired me about what a researcher should do.
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