협동통신 네트워크에서 다이버시티 및 자유도에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 노종선.This dissertation contains the following three contributions to the interesting research topics on diversity techniques and interference alignment (IA) for cooperative communication networks. *Relay on-off threshold (ROT) for non-orthogonal decode and forward (NDF) protocol with distributed orthogonal space-time block codes (DOSTBCs) - Calculate the optimal ROT for NDF protocol with DOSTBCs in high signal to noise power ratio (SNR) region. - Propose suboptimal ROT for NDF protocol with DOSTBCs in low SNR region. - Analyze the diversity order of the proposed scheme. *New IA schemes aided by relays for quasi-static MX2 X channel - Propose IA scheme aided by one full-duplex relay. - Propose IA scheme aided by two half-duplex relay. - Prove that the proposed IA schemes achieve the maximum degrees of freedom (DoF) for quasi-static MX2 X channel. * Selection diversity on the IA for multi-input and multi-output (MIMO) interference channel - Propose the selection criterion of beamforming matrices of IA for MIMO interference channel. - Analyze the diversity order of the proposed scheme. First, we construct the DOSTBCs using source and relay in the cooperative communication networks. In order to decode the DOSTBCs, the destination uses the linear combining (LC) decoding scheme. In this system models, the symbol error rate (SER) is formulated and the ROT is calculated to minimize the SER. It is proved that the full diversity order of NDF protocol can be achieved by using the relay on-off scheme with the optimal threshold. In the second part of this dissertation, two new IA schemes aided by relays for quasi-static MX2 X channel are proposed. The first proposed scheme uses one full-duplex relay and it can achieves the maximum DoF. However, at the full-duplex relay, the transmit signal can be strong self-interference, called echo and thus it is difficult to implement practically. To resolve this problem, at the second proposed IA scheme, two half-duplex relays are used and it is proved that the second proposed IA scheme can also achieve the maximum DoF of MX2 X channel. Finally, the selection scheme for IA is proposed for MIMO interference channel. Most of IA schemes are focused on DoF but there is only a few research results for diversity order which is a crucial measure of reliability. Therefore, we propose a selection criterion to minimize SER and analyze the diversity order of the proposed scheme in the MIMO interference channel.Abstract i Contents iv List of Tables vii List of Figures viii 1. Introduction 1.1. Background 1.2. Overview of Dissertation 1.3. Terms and Notations 2. Diversity Techniques and Interference Alignment 2.1. MIMO Communications 2.2. Space-Time Coding and Selection Diversity 2.3. Cooperative Communications 2.4. Interference Alignment 3. Relay On-Off Threshold for NDF Protocol with Distributed Orthogonal Space-Time Block Codes 3.1. Introduction 3.2. System Models and Linear Combining Decoding 3.2.1. System Models of NDF Protocol 3.2.2. Linear Combining Decoding 3.3. Relay On-Off Threshold and Diversity Analysis 3.3.1. Relay On-Off Threshold 3.3.2. Relay On-Off Threshold for LC Decoding 3.3.3. Decision of Suboptimal Relay On-Off Threshold in Low SNR Region 3.3.4. Diversity Analysis 3.4. Numerical Analysis 3.5. Conclusion 4. New Interference Alignment Scheme Aided by Relays for Quasi-Static X Channels 4.1. Introduction 4.2. Preliminaries: X Channel and Interference Alignment 4.3. The Proposed Schemes and System Models 4.3.1. Two Proposed Schemes 4.3.2. System Models for the Proposed Schemes 4.4. Achievability of the Proposed IA Schemes 4.4.1. IA Scheme with a Full-Duplex Relay 4.4.2. IA Scheme with Two Half-Duplex Relays 4.5. Achievability of the Proposed IA Schemes for the 2×M X Channel 4.6. Numerical Analysis 4.7. Conclusion 5. Selection Diversity on the Interference Alignment for MIMO Interference Channels 5.1. Introduction 5.2. Characteristic Function of Multivariate Rayleigh Random Variables 5.3. Combining IA and Selection Schemes for 3-User MIMO Interference Channel 5.3.1. System Model and IA for 3-User MIMO Interference Channel 5.3.2. Orthogonalization of Beamforming Matrices 5.3.3. Selection of Beamforming Matrices 5.4. Diversity Analysis 5.5. Simulation Results 5.6. Conclusions 6. Conclusions Bibliography 초록Docto

Propagation measurement based study on relay networks

Von der nächsten Generation von Mobilfunksystemen erwartet man eine umfassende Versorgung mit breitbandigen Multimediadiensten. Um die dafür erforderliche flächendeckende Versorgung mit hohen Datenraten zu gewährleisten, können Relay-Netzwerke einen wesentlichen Beitrag liefern. Hierbei werden Netzwerkstationen mit Relay-Funktionalität in zellulare Netzwerke integriert. Diese Dissertation befasst sich mit der Untersuchung Relay-basierter Netzwerke unter Verwendung von Ausbreitungsmessungen. Die Arbeit deckt Fragen zur Kanalmodellierung, Systemevaluierung bis hin zur Systemverifikation ab. - Zunächst wird ein auf Funkkanalmessungen beruhendes experimentelles Kanalmodell für Relay-Netzwerke vorgestellt. Im Weiteren werden technische Verfahren für Mehrfachzugriffs-Relay-Netzwerke MARN diskutiert. Die erreichbare Systemleistung wurde unter Verwendung von Rayleigh-Kanälen innerhalb einer Systemsimulation bestimmt und im Anschluss mit realen Kanälen, die sowohl direkt aus Funkkanalmessungen als auch indirekt aus dem bereits erwähnten Kanalmodell abgeleitet wurden, verifiziert. Bisherige Arbeiten zur Modellierung breitbandiger Multiple-Input Multiple-Output (MIMO) Kanäle berücksichtigen nicht oder nur sehr stark vereinfacht die Langzeitkorrelationseigenschaften zwischen den Links und werden damit der vermaschten und räumlich weit verteilten Topologie von Relay-Netzwerken gerecht. In der vorliegenden Dissertation erfolgte daher eine experimentelle Untersuchung zu den Korrelationseigenschaften von Large-Scale-Parametern LSP, die unter Verwendung von Funkkanalmessdaten aus urbanen Umgebungen und aus Innenräumen abgeleitet wurden. Die Ergebnisse hierzu fanden Eingang in das vom WINNER-Projekt entwickelte Kanalmodell. Sie erlauben damit eine realistischere Simulation von Relay-unterstützten Netzen. Einen weiteren Schwerpunkt dieser Arbeit stellen technische Verfahren dar, die eine Erhöhung der Systemleistung in MARN mit unbekannter Interferenz UKIF versprechen. Im Einzelnen handelt es sich um die Mehrfachzugriffs-Kodierung MAC - die eine verbesserte Signaltrennung auf der Empfängerseite und eine Erhöhung des Datendurchsatzes erlaubt, den Entwurf eines Relay-Protokolls zur Erhöhung der Systemeffizienz, einen Minimum Mean Square Error (MMSE) Algorithmus zur Unterdrückung unbekannter Interferenzen bei Erhaltung der MAC-Signalstruktur mehrerer Mobilstationen MS, und ein fehlererkennungsbasiertes Signalauswahlverfahren zur Diversitätserhöhung. Die vorgenannten Verfahren werden in einer Systemsimulation zunächst mit Rayleigh-Kanälen evaluiert und demonstrieren die erzielbare theoretische Leistungssteigerung. Die Berücksichtigung realer Funkkanäle innerhalb der Systemsimulation zeigt allerdings, dass die theoretische Systemleistung so in der Realität nicht erreichbar ist. Die Ursache hierfür ist in den idealisierten Annahmen theoretischer Kanäle zu suchen. Für die Entwicklung künftiger Relay-Netzwerke bieten die in dieser Arbeit aufbereiteten Erkenntnisse hinsichtlich der Langzeitkorrelationseigenschaften zwischen den Links einen wertvollen Beitrag für die Abschätzung ihrer Systemleistung auf der Basis eines verbesserten Kanalmodells.Considering technological bases of next generation wireless systems, it is expected that systems can provide a variety of coverage requirements to support ubiquitous communications. To satisfy the requirements, an innovative idea, integrating network elements with a relaying capability into cellular networks, is one of the most promising solutions. The main topic of this dissertation is a propagation measurement based study on relay networks. The study includes three parts: channel modeling, performance evaluation, and verification. First of all, an empirical channel model for relay networks is proposed based on statistical analyses of measurement data. Then, advanced techniques for the throughput improvement and interference cancellation are proposed for Multiple Access Relay Networks (MARN) which are used as an example of relay networks. The performance of the considered MARN is evaluated for Rayleigh channels, and then verified for realistic channels, obtained from measurement data and from the experimental relay channel model as well. For relay channel modeling, the long-term correlation properties between links are of crucial importance due to the meshed-network topology. Although, there is a wide variety of research results for Multiple-Input Multiple-Output (MIMO) channel modeling available, the characterization of correlation properties has been significantly simplified or even completely ignored which motivates this research to be performed. In this dissertation, the experimental results of the correlation properties of Large Scale Parameters (LSP) are presented through the analysis on the real-field measurement data for both the urban and indoor scenarios. furthermore, the correlation properties have been fully introduced into the WINNER channel Model (WIM) for realistic relay channel simulations. As a further contribution of this dissertation, various advanced techniques are proposed for MARN in the presence of Unknown Interference (UKIF). Multiple Access Coding (MAC) is introduced as a multiple access technique. The use of MAC provides the signal separability at the receiver and improves throughput. Thereafter, high system resource efficiency can be achieved through relay protocol design. At the receiver, Minimum Mean Square Error (MMSE)-based spatial filtering is used to suppress UKIF while preserving multiple Mobile Station (MS)s’ MAC-encoded signal structure. Furthermore, an error detection aided signal selection technique is proposed for diversity increasing. The theoretical system performance with aforementioned techniques is simulated for Rayleigh channels. Thereafter, realistic channels are exploited for the performance verification. The gap between the theoretical performance and the realistic performance indicates that the assumptions made to the simplified Rayleigh-channels do not fully hold in reality. For the future relay system design, this work provides valuable information about the performance evaluation of relay networks in consideration of the correlation properties between links

同時送信型無線ネットワークの物理層に関する研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 森川 博之, 東京大学教授 相田 仁, 東京大学教授 廣瀬 明, 東京大学准教授 中山 雅哉, 東京大学准教授 落合 秀也University of Tokyo(東京大学

Belle II Technical Design Report

The Belle detector at the KEKB electron-positron collider has collected almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an upgrade of KEKB is under construction, to increase the luminosity by two orders of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2 /s luminosity. To exploit the increased luminosity, an upgrade of the Belle detector has been proposed. A new international collaboration Belle-II, is being formed. The Technical Design Report presents physics motivation, basic methods of the accelerator upgrade, as well as key improvements of the detector.Comment: Edited by: Z. Dole\v{z}al and S. Un

Integrated Quantum Key Distribution sender unit for hand-held platforms

Mastering the generation, propagation and detection of electro-magnetic waves has enabled a technological breakthrough that has changed our entire society. World-wide communication through the telephone and the internet has become an integral part of our daily-life, which is expected to grow even further with the emergence of the internet of things. While secure communication was of concern mostly for governmental and financial institutions, digital security has now caught the attention of the general public. The weaknesses of cur- rent encryption protocols, such as the existence of back-doors or the predicted breakdown of popular algorithms such as RSA, reveal the need for alternative encryption schemes ensuring unconditional security on all types of devices. Quantum Key Distribution (QKD) has emerged as a powerful option to ensure a private communication between two users. Based on the laws of quantum mechanics, this class of protocols offers the possibility to detect the presence of a third party trying to intercept the key during its distribution, and even to quantify the amount of leaked information. While most research projects focus on long distance applications, little attention has been devoted to short distance schemes such as wireless payment, network access and authentication, which could highly benefit from QKD-enhanced security. This thesis focuses on the development of a miniature QKD sender add-on that could be embedded either in mobile devices or in existing optical communication platforms, thus allowing for a secure key exchange with a shared dedicated receiver over a free- space link. The proposed optics architecture (35 × 20 × 8 mm 3 ) is optimised for BB84-like protocols and uses an array of four Vertical-Cavity Surface-Emitting Lasers with highly similar properties to generate 40 ps long near-infrared faint coherent pulses at 100 MHz repetition rate. Under strong modulation, the polarisation of the pulses is not well defined and enables an external control of each diode’s emission by a wire-grid polariser. The four beams are spatially overlapped in a polarisation-insensitive femtosecond laser written waveguide array, and combined with a red beacon laser using an external beamsplitter to ensure a stable, synchronised optical link with the receiver. The complete module is compatible with current smartphone technology, allowing to run the classical post-processing over WLAN in the future. First tests with a free-space receiver indicate an average error ratio of 3.3 % and an asymptotic secure key rate of 54 kHz under static alignment. For the first time, a secure key exchange between a mobile platform held by a user and a receiver equipped with a dynamic alignment system could be demonstrated with an error ratio of 4.1 % and a secure key rate of 31 Hz. The further optimisation of the experimental parameters and the implementation of a decoy protocol will enhance the key generation rate as well as the general security of the system. The results of this thesis pave the way towards unprecedented security in wireless optical networks, as examplified for the communication between a mobile device and a dedicated receiver.Die Fähigkeit, elektromagnetische Strahlung kontrolliert zu erzeugen, gerichtet zu emittieren sowie zu detektieren stellte einen technologischen Durchbruch dar, der die ganze Gesellschaft verändert hat. Weltweite Kommunikation und Datenübertragung mittels Radiowellen, dem Telefon und dem Internet wurde zu einem wesentlichen Bestandteil des täglichen Lebens. Es ist zu erwarten, dass durch das Internet der Dinge die übertragene Datenmenge weiter zunehmen wird. Während zunächst vor allem Regierungen und Banken an Methoden für sichere Datenübertragung interessiert waren, wurde die Frage nach digitaler Sicherheit mit der Entwicklung mobiler Geräte, die immer mehr persönliche Daten sammeln und übertragen, in die breite Offentlichkeit getragen. Die Schwachpunkte aktueller Verschlüsselungstechnologien, wie z.B mögliche Hintertüren in existierenden Implementierungen oder das in absehbarer Zeit erwartete Brechen des weit verbreiteten RSA- Algorithmus, zeigen die Notwendigkeit alternativer Verfahren, deren Sicherheit nicht von zusätzlichen, mitunter nicht überprüfbaren Annahmen abhängt. Quantenschlüsselübertragung (engl. Quantum Key Distribution, QKD) stellt eine leistungsfähige Alternative dar, um verschlüsselte Kommunikation zwischen zwei Benutzern mithilfe eines gemeinsamen sicheren Schlüssels zu ermöglichen. Aufbauend auf den Gesetzen der Quantenmechanik ermöglicht es diese Klasse von Protokollen, eine dritte Partei beim Abhören des Schlüssels zu detektieren. Ebenso kann die Menge der möglicherweise abgefangenen Daten quantifiziert werden. Die meisten Forschungsprojekte konzentrierten sich bisher auf die Kommunikation über weite Strecken, wohingegen Anwendungen über kurze Entfernungen, wie z.B. handybasierte Bezahlmethoden oder Zugang und Authentifizierung in einem Netzwerk weitgehend vernachlässigt wurden, obwohl auch diese Anwendungen von der verbesserten Sicherheit durch QKD profitieren könnten. Die vorliegende Arbeit beschäftigt sich mit der Entwicklung einer miniaturisierten QKD Sendeeinheit für den sicheren Schlüsselaustausch über eine Freistrahlverbindung mit einem Empfänger, wie sie als Erweiterung für mobile Geräte oder bestehende optische Kommunikationsinfrastruktur verwendet werden könnte. Das vorgeschlagene Design des optischen Chips (35 × 20 × 8 mm³) ist für Protokolle, die sich an BB84 anlehnen optimiert und verwendet eine Anordnung von vier praktisch nicht zu unterscheidenden Oberflächenemittern (Vertical-Cavity Surface-Emitting Laser, VCSEL) die schwache, kohärente Pulse mit 40 ps Länge im nahen Infrarotbereich mit einer Wiederholrate von 100 MHz erzeugen. Bei starker Modulation ist die Polarisation der Pulse unbestimmt und kann daher mithilfe eines Gitterpolarisators für jede Diode separat eingestellt werden. Die vier Strahlen werden räumlich in einem optischen Wellenleiter, der mit einem Femtosekundenlaser geschrieben wurde und unabhängig von der Polarisation arbeitet, überlappt. Anschließend werden sie an einem externen Strahlteiler mit einem weiteren Laser im sichtbaren Bereich zusammengeführt. Dieser dient dazu, eine synchronisierte Verbindung zum Empfänger herzustellen. Das komplette Modul ist kompatibel mit aktueller Smartphonetechnik, wodurch ein klassischer Kanal, der für die Datennachbearbeitung benötigt wird, über LTE oder WLAN zur Verfügung gestellt werden kann. Erste Freistrahltests, bei denen Sender und Empfänger fixiert waren, ergaben eine durchschnittliche Fehlerrate von 3,3 % und eine asymptotische sichere Schlüsselrate von 54 kHz. Zum ersten Mal konnte auch ein sicherer Schlüsselaustausch zwischen einem vom Nutzer in der Hand gehaltenem mobilen Gerät und einem mit einem dynamischen Justagesystem ausgestatteten Empfänger gezeigt werden. Die Fehlerrate lag hierbei bei 4,1 % und die sichere Schlüsselrate bei 31 Hz. Durch eine weitere Optimierung der experimentellen Parameter sowie der Implementierung eines sogenannten Decoyprotokolls wird sich die Schlüsselrate sowie die Sicherheit des Systems noch deutlich erhöhen lassen. Zusammenfassend stellen diese Ergebnisse, exemplarisch gezeigt anhand der Kommunikation zwischen einem mobilen Gerät und einem stationren Empfänger, einen ersten Schritt hin zu bisher unerreichter Sicherheit in drahltlosen Netzwerken dar

Towards Personalized Healthcare in Cardiac Population: The Development of a Wearable ECG Monitoring System, an ECG Lossy Compression Schema, and a ResNet-Based AF Detector

Cardiovascular diseases (CVDs) are the number one cause of death worldwide. While there is growing evidence that the atrial fibrillation (AF) has strong associations with various CVDs, this heart arrhythmia is usually diagnosed using electrocardiography (ECG) which is a risk-free, non-intrusive, and cost-efficient tool. Continuously and remotely monitoring the subjects' ECG information unlocks the potentials of prompt pre-diagnosis and timely pre-treatment of AF before the development of any life-threatening conditions/diseases. Ultimately, the CVDs associated mortality could be reduced. In this manuscript, the design and implementation of a personalized healthcare system embodying a wearable ECG device, a mobile application, and a back-end server are presented. This system continuously monitors the users' ECG information to provide personalized health warnings/feedbacks. The users are able to communicate with their paired health advisors through this system for remote diagnoses, interventions, etc. The implemented wearable ECG devices have been evaluated and showed excellent intra-consistency (CVRMS=5.5%), acceptable inter-consistency (CVRMS=12.1%), and negligible RR-interval errors (ARE<1.4%). To boost the battery life of the wearable devices, a lossy compression schema utilizing the quasi-periodic feature of ECG signals to achieve compression was proposed. Compared to the recognized schemata, it outperformed the others in terms of compression efficiency and distortion, and achieved at least 2x of CR at a certain PRD or RMSE for ECG signals from the MIT-BIH database. To enable automated AF diagnosis/screening in the proposed system, a ResNet-based AF detector was developed. For the ECG records from the 2017 PhysioNet CinC challenge, this AF detector obtained an average testing F1=85.10% and a best testing F1=87.31%, outperforming the state-of-the-art

Heterogeneous wireless networks for smart cities

In the near future, a world of smart cities is envisioned in which many devices equipped with sensors and communication interfaces can be used to collect and share data in order to derive maps or infer information on some parameter of interest. Wireless technologies are enabling this smart city paradigms, where many items are networked for the growth of society. This scenario opens new challenges to wireless network designers, with new performance metrics, coverage and privacy needs, as well as the need for a tighter integration of different networks. This is the fundamental concept of Heterogeneous Networks. Enclosing humans in the loop, through crowdsensing techniques, will dramatically increase the amount of data available for the mapping process, with obvious benefits in terms of the resulting accuracy. On the other hand, the huge amount of data generated represents also a challenge that, along with the irregular, uncontrollable, spatial distribution of measurements represent serious challenges to be addressed. Another important aspect of smart cities scenarios is represented by vehicular networks. Several technologies have been proposed to address such application. Among the others, an interesting solution is provided by Visible Light Communications (VLC). Based on the use of the light emission diodes (LEDs) that are already available on the majority of vehicles, VLC would enable short range communication in large, unlicensed, and uncongested bands with limited costs. In the framework of smart cities scenarios, my research activity aimed at formulating and solving some of the issues arising from the envisioned challenging services, with both analytical and simulation-based approaches

Highly Multiplexed Superconducting Detectors and Readout Electronics for Balloon-Borne and Ground-Based Far-Infrared Imaging and Polarimetry

abstract: This dissertation details the development of an open source, frequency domain multiplexed (FDM) readout for large-format arrays of superconducting lumped-element kinetic inductance detectors (LEKIDs). The system architecture is designed to meet the requirements of current and next generation balloon-borne and ground-based submillimeter (sub-mm), far-infrared (FIR) and millimeter-wave (mm-wave) astronomical cameras, whose science goals will soon drive the pixel counts of sub-mm detector arrays from the kilopixel to the megapixel regime. The in-flight performance of the readout system was verified during the summer, 2018 flight of ASI's OLIMPO balloon-borne telescope, from Svalbard, Norway. This was the first flight for both LEKID detectors and their associated readout electronics. In winter 2019/2020, the system will fly on NASA's long-duration Balloon Borne Large Aperture Submillimeter Telescope (BLAST-TNG), a sub-mm polarimeter which will map the polarized thermal emission from cosmic dust at 250, 350 and 500 microns (spatial resolution of 30", 41" and 59"). It is also a core system in several upcoming ground based mm-wave instruments which will soon observe at the 50 m Large Millimeter Telescope (e.g., TolTEC, SuperSpec, MUSCAT), at Sierra Negra, Mexico. The design and verification of the FPGA firmware, software and electronics which make up the system are described in detail. Primary system requirements are derived from the science objectives of BLAST-TNG, and discussed in the context of relevant size, weight, power and cost (SWaP-C) considerations for balloon platforms. The system was used to characterize the instrumental performance of the BLAST-TNG receiver and detector arrays in the lead-up to the 2019/2020 flight attempt from McMurdo Station, Antarctica. The results of this characterization are interpreted by applying a parametric software model of a LEKID detector to the measured data in order to estimate important system parameters, including the optical efficiency, optical passbands and sensitivity. The role that magnetic fields (B-fields) play in shaping structures on various scales in the interstellar medium is one of the central areas of research which is carried out by sub-mm/FIR observatories. The Davis-Chandrasekhar-Fermi Method (DCFM) is applied to a BLASTPol 2012 map (smoothed to 5') of the inner ~1.25 deg2 of the Carina Nebula Complex (CNC, NGC 3372) in order to estimate the strength of the B-field in the plane-of-the-sky (B-pos). The resulting map contains estimates of B-pos along several thousand sightlines through the CNC. This data analysis pipeline will be used to process maps of the CNC and other science targets which will be produced during the upcoming BLAST-TNG flight. A target selection survey of five nearby external galaxies which will be mapped during the flight is also presented.Dissertation/ThesisDoctoral Dissertation Astrophysics 201

Visible Light Communication (VLC)

Visible light communication (VLC) using light-emitting diodes (LEDs) or laser diodes (LDs) has been envisioned as one of the key enabling technologies for 6G and Internet of Things (IoT) systems, owing to its appealing advantages, including abundant and unregulated spectrum resources, no electromagnetic interference (EMI) radiation and high security. However, despite its many advantages, VLC faces several technical challenges, such as the limited bandwidth and severe nonlinearity of opto-electronic devices, link blockage and user mobility. Therefore, significant efforts are needed from the global VLC community to develop VLC technology further. This Special Issue, “Visible Light Communication (VLC)”, provides an opportunity for global researchers to share their new ideas and cutting-edge techniques to address the above-mentioned challenges. The 16 papers published in this Special Issue represent the fascinating progress of VLC in various contexts, including general indoor and underwater scenarios, and the emerging application of machine learning/artificial intelligence (ML/AI) techniques in VLC