Fundamental Limits of Wideband Localization

Location-awareness is essential for many wireless network applications. However, determining nodes' positions precisely is a challenging task, especially in harsh multipath propagation environments. To address this problem, wide bandwidth signals are envisioned to be used in future localization systems, since such signals can provide accurate range measurements. In this paper, we investigate the localization performance of wideband networks and proposed a performance measure called the squared position error bound (SPEB) to characterize the localization accuracy. We derive the SPEB succinctly by applying the notion of equivalent Fisher information (EFI). The EFI provides insights into the essence of localization problem by unifying the localization information from individual anchors and that from a priori knowledge of the agent's position in a canonical form. We also investigate the use of wideband antenna arrays and the effect of clock asynchronism on the localization accuracy. Our analysis begins with the received waveforms themselves rather than utilizing only signal metrics, such as time-of-arrival and received signal strength, extracted from the waveforms. Our framework exploits all the information inherent in the received waveforms, and therefore the SPEB serves as a fundamental limit of localization accuracy. Thesis Supervisor: Moe Z. Win Title: Associate Professor Acknowledgments I would like to gratefully acknowledge all people who contributed to this thesis. First and foremost, I would like to express my deep and sincere gratitude to my advisor, Professor Moe Win, for his patient guidance and encouragement over the past two years. From him, I have gained invaluable insights and self-confidence with respective to both my work and my life, which has made research life smooth and rewarding for me. Professor Win has been a wonderful mentor and friend. I cannot overstate my gratitude for his support. I am greatly indebted to Henk Wymeersch and Wesley Gifford for their inspiration and help. Without their generous help with research techniques, as well as with grammar, this thesis would not have been possible. I especially want to thank Wes for sharing his broad knowledge and experience on topics ranging from course study to carpentry and from VNA operation to car suspension, since the very first day I joined the group. I am grateful to all the members of the W group-Tony, Ae, Wee-Peng, Pedro, Jaime, Kampol, Ulric, Stephano, and Pisit-for their friendship and support. I have truly enjoyed getting to know each of you, both in and outside work. Thank you for sharing your knowledge, for making the office a fun place to be, and for organizing each of the fantastic group activities. To all my friends, old and new, thank you for sharing both the ups and the downs of this process with empathy and laughter. Finally, I cannot express the full extent of my gratitude to my parents, Zhongchen and Yiqin, for their love, persistent confidence, and unwavering support in everything I do.