처프 신호를 이용한 음파 통신 기법 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 최성현.Todays smart devices such as smartphones and tablet/wearable PCs are equipped with voice user interface (UI) in order to support intuitive command input from users. Speakers and microphones of the voice UI are generally used to play and record human voice and/or environmental sound, respectively. Accordingly, various aerial acoustic communication techniques have been introduced to utilize the voice UI as an additional communication interface beyond WiFi and/or Bluetooth. Smart devices are especially suitable for the aerial acoustic communication since the application processor (AP) of smart devices can process the sound to embed or fetch information in it. That is, smart devices work similar to software defined radio platform. The aerial acoustic communication is also very versatile as any audio interface can be utilized as a communication interface. In this dissertation, we propose an aerial acoustic communication technique using inaudible chirp signal as well as corresponding receiver architecture for smart devices. We additionally introduce the applications of the proposed communication technique in indoor environments. We begin the receiver design for aerial acoustic communication by measuring the characteristics of indoor acoustic channel, composed of speaker, air-medium, and microphone. Our experimental research reveals that the indoor acoustic channel typically has long delay spread (approximately 40 msec), and it is very frequency-selective due to the frequency response of audio interfaces. We also show that legacy physical layer (PHY) modulation schemes such as phase/frequency shift keying (PSK/FSK) are likely to fail in this indoor acoustic channel, especially in long communication scenarios, due mainly to the instability of local oscillator and frequency selectivity of audio interfaces. In order to resolve the above-mentioned problems, we use chirp signals for the aerial acoustic communication. The proposed acoustic receiver supports long-range communication independent of the device characteristics over the severely frequency-selective acoustic channel with large delay spread. The chirp signal has time-varying frequency with a specific frequency sweeping rate. The chirp signal was widely used for radar applications due to its capability of resolving multi-path propagation. However, this dissertation is the first study of adopting chirp signal in aerial acoustic communications for smart devices. The proposed receiver architecture of chirp binary orthogonal keying (BOK) can be easily implemented via fast Fourier transform (FFT) in smart devices application layer. Via extensive experimental results, we verify that the proposed chirp signal can deliver data at 16 bps up to 25 m distance in typical indoor environments, which is drastically extended compared to the few meters of previous research. The data rate of 16 bps is enough to deliver short identification (ID) in indoor environments. The exemplary applications with this short ID can be multimedia content recognition and indoor location tracking. The low data rate, however, might be a huddle of the proposed system to be applied to the services that require high data rate. We design a backend server architecture in order to compensate for the low data rate and widen the application extent of the proposed receiver. The smart devices can send queries in order to refer to the backend server for additional information that is related with the received ID. We also propose an energy-efficient recording and processing method for the acoustic signal detection. Note that it would consume huge amount of energy if the smart devices contiguously sensed the acoustic signal for 24 hours. The smart devices instead control the sensing (i.e., recording) timing so that it is activated only when there exists chirp signal. This can drastically extend the battery lifetime by removing unnecessary signal processing. We also present two application examples of the proposed receiver, namely, (1) TV content recognition, and (2) indoor location tracking, including technical discussions on their implementations. Experiments and field tests validate the feasibility of the proposed aerial acoustic communication in practical environments.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Acoustic communication . . . . . . . . . . . . . . . . . 1 1.1.1 Underwater acoustic communication . . . . . 2 1.1.2 Aerial acoustic communication . . . . . . . . . . 3 1.2 Overview of Existing Approaches . . . . . . . . . . . 5 1.2.1 Indoor Location Tracking . . . . . . . . . . . . . . . 5 1.2.2 Data Communication using Acoustic Signal . 7 1.2.3 Commercial Services . . . . . . . . . . . . . . . . . . 9 1.2.4 Limitations of Previous Work . . . . . . . . . . . 10 1.3 Main Contributions . . . . . . . . . . . . . . . . . . . . . 11 1.3.1 Acoustic Channel and PHY Analysis . . . . . . 12 1.3.2 Receiver Design for Acoustic Chirp BOK . . . 12 1.3.3 Applications of Chirp BOK Receiver . . . . . . 13 1.4 Organization of the Dissertation . . . . . . . . . . 13 2 Acoustic Channel and PHY Analysis . . . . . . . . . . 15 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.2 Characteristics of Indoor Acoustic Channel . . 18 2.2.1 Hearing Threshold of Human . . . . . . . . . . . 18 2.2.2 Frequency Response of Various Audio Interfaces . 21 2.2.3 Delay Spread of Acoustic Channel . . . . . . . . 25 2.3 Revisit of Existing Modulation Schemes . . . . . . 26 2.3.1 Case Study: Phase Shift Keying . . . . . . . . . . 28 2.3.2 Case Study: Frequency Shift Keying . . . . . . . 35 2.3.3 Chirp Binary Orthogonal Keying (BOK) . . . . 40 2.4 Performance Evaluation of PHY Modulation Schemes . 42 2.4.1 Experimental Environment . . . . . . . . . . . . . . 44 2.4.2 PSK Demodulator . . . . . . . . . . . . . . . . . . . . . 44 2.4.3 FSK Demodulator . . . . . . . . . . . . . . . . . . . . . 45 2.4.4 BER of PHY Modulation Schemes . . . . . . . . . 46 2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3 Receiver Design for Acoustic Chirp BOK . . . . . . . 49 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2 Chirp Signals and Matched Filter Receiver . . . . . 51 3.2.1 Notation of Chirp Signals . . . . . . . . . . . . . . . 51 3.2.2 Matched Filter and FFT . . . . . . . . . . . . . . . . . 53 3.2.3 Envelope Detection of Chirp Auto Correlation . 55 3.3 System Design and Receiver Architecture . . . . . . 59 3.3.1 Frame and Symbol Design . . . . . . . . . . . . . . . 60 3.3.2 Signal Reception Process . . . . . . . . . . . . . . . . 63 3.3.3 Receiver Architecture . . . . . . . . . . . . . . . . . . . 65 3.3.4 Symbol combining for BER enhancement . . . . 68 3.4 Performance Evaluation of Chirp BOK Receiver . . 73 3.4.1 Experimental Environment . . . . . . . . . . . . . . . . 74 3.4.2 Transmission Range in Indoor Environment . . . 74 3.4.3 Multi-path Resolution Capability of Chirp Signal . 75 3.4.4 Symbol Sampling and Doppler Shift . . . . . . . . . 82 3.4.5 Selective combining . . . . . . . . . . . . . . . . . . . . . 85 3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 4 Applications of Chirp BOK Receiver . . . . . . . . . . . . . . 90 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 4.2 Backend Server Architecture . . . . . . . . . . . . . . . . . . 93 4.2.1 Implementation of Backend Server . . . . . . . . . . 93 4.2.2 Operation of Backend Server . . . . . . . . . . . . . . 95 4.3 Low Power Operation for Smart Devices . . . . . . . . 98 4.3.1 Reception Process of Chirp BOK receiver . . . . . . 98 4.3.2 Revisit of Signal Detection in Wireless Communications ... 100 4.3.3 Chirp Signal Detection using PSD . . . . . . . . . . . 102 4.3.4 Performance Evaluation of Signal Detection Algorithm . 105 4.4 Applications of Chirp BOK Receiver and Feasibility Test . . 110 4.4.1 TV Content Recognition . . . . . . . . . . . . . . . . . . . 111 4.4.2 Indoor Location Tracking in Seoul Subway . . . . . 114 4.4.3 Device to Device Communication . . . . . . . . . . . . 118 4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 5 Conclusion and Future Work . . . . . . . . . . . . . . . . . . . 123 5.1 Research Contributions . . . . . . . . . . . . . . . . . . . . . . 123 5.2 Future Work and Concluding Remark . . . . . . . . . . 125 Abstract (In Korean) . . . . . . . . . . . . . . . . . . . . . . . . 136Docto

The integration of device-to-device communication in future cellular systems

The usage of mobile data services over cellular spectrum has been dramatically increased in the last decade. The increment led to an explosive growth in user’s booming data demands over the cellular spectrum band. However, the current technologies have a limitation in the allocated spectrum resources, compared to the data demands. This leads to insufficient throughput using the current technologies in the next few years. Improving the throughput with user’s data demands necessitates finding an efficient approach to offload data booming. Device-to-Device (D2D) communication has been proposed as an unconventional mobile paradigm with a scalable manner to offload the mobile data traffic of the local peer-to-peer mobile users by sharing the resources the cellular networks without traversing the base stations. Applying such paradigm increases the spectrum utilization which improves the total throughput in a given cell. However, many issues negatively influence the performance of D2D communication over the cellular spectrum band such as interference from the cellular users, the low activity of the cellular users over the allocated resources in time which reduces spectrum utilization and the dynamic cellular environment which impacts the link performance of D2D communication and may leads to not meet the desired quality of service requirements of the data services. Solving the aforementioned issues requires: i) developing the appropriate access paradigms of the D2D communication to meet the desired quality of service requirements of mobile data services; ii) increasing the spectrum utilization of licensed band by enabling unlicensed users to invest the spectrum holes; and iii) developing the link adaptation processes to overcome the dynamic behavior of the cellular system and improve the throughput in D2D communication links. This dissertation presents the aforementioned solutions for the D2D communication which improve the total throughput in the cell. The dissertation has three main contributions: i) position-based hybrid access paradigm for D2D communication; ii) hybrid access paradigm for unlicensed peer-to-peer users (unlicensed D2D communication); and iii) an algorithm for link adaptation of unlicensed D2D communication. First, the thesis develops a position-based model for maximizing the throughput of D2D communication using different access paradigms. This model defines the regions in the cell in which the D2D communication can be performed with the desired QoS. Then, a position-based hybrid access paradigm is presented which selects a given access paradigm used by D2D pairs in order to improve the total throughput in the cell. The proposed access paradigms are evaluated using numerical simulations and the results show improvements in the total throughput and the number of satisfied D2D communications in the cell, compared to recent access paradigms. Second, an integration of cognitive radio technology with the unlicensed D2D pairs to apply dynamic spectrum access is presented. The recent access paradigms of cognitive radio and their achievable throughput are studied. Then, a position-based hybrid access paradigm is introduced to increase the regions of unlicensed D2D communication. The evaluation of the proposed access paradigm is performed using numerical simulations. The results show improvement in the throughput over the cell and the area used by unlicensed D2D communications, compared to recent access paradigms. Third, the dynamic behavior of the cellular environment and its interaction with the unlicensed D2D communication is studied. One possible solution presented applying artificial intelligence technique as a cognitive engine to perform link adaptation efficiently. Based on this study, a Self-Organized Link Adaptation (SOLinA) algorithm is presented to adapt the link of unlicensed D2D communication autonomously and determine the link configuration which improves the throughput of the system. The evaluation of the proposed algorithm is performed using simulations of unlicensed D2D communication within dynamic cellular environment. The results of the simulations show that SOLinA outperforms the previous work in the throughput under different separations between the unlicensed D2D communication, different cellular system requirements and at different user’s positions in the cell.In der letzten Dekade nahm der Einsatz mobile Datendienste in zellularen Netzen stark zu und führte zu einem exponentiellen Anstieg der Nutzerdaten. Die aktuellen Technologien weisen jedoch, bezogen auf das geforderte Datenvolumen, Einschränkungen auf, die auch in den kommenden Jahren zu einem unzureichenden Durchsatz führen werden. Die Erhöhung des Durchsatzes für Nutzerdaten erfordert die Suche nach einem effizienten Ansatz um das steigende Datenvolumen zu bewältigen. Ein möglicher Ansatz ist Device-to-Device (D2D) Kommunikation als ein unkonventionelles, mobiles Paradigma, das hohen Datenverkehr skalierbar auf lokale Peer-to -Peer- Anwender überträgt. Dabei werden die Ressourcen zwischen D2D- und zellularen Nutzern aufgeteilt, wobei der D2DDatenverkehr direkt zwischen Endgeräten, d.h. ohne Einsatz der Basis Station erfolgt. Dadurch kann das Frequenzspektrum effizienter genutzt, und somit der Gesamtdurchsatz der Zelle erhöht werden. Zugleich wirken sich mehrere Faktoren negativ auf den Durchsatz der D2D-Kommunikation im zellularen Spektralband aus, wie z. B. die Interferenz zellularer Endgeräte, die weiterhin direkt mit der Basisstation kommunizieren. Zusätzlich reduziert geringe Aktivität der zellularen Endgeräte über die zugewiesenen Ressourcen die Spektraleffizienz, mit negativer Auswirkung auf den Durchsatz der D2DVerbinding. Das kann dazu führen, dass die gewünschte Qualität des Datendiensts nicht erreicht wird. Die Lösung der oben genannten Probleme erfordert: i) die Entwicklung entsprechender Zugriffsmechanismen für die D2D-Kommunikation, um die gewünschte Qualität der Service-Anforderungen mobiler Datendienst zu erreichen; ii) die Auslastung des Funkspektrums des lizenzierten Bands zu erhöhen, indem nicht lizenzierten Nutzern temporär freie Bereiche des Spektrums verwenden; und iii) die Entwicklung eines Prozesses zur Link-Adaption unter Berücksichtigung des dynamischen Verhaltens des zellularen Systems, so dass sich der Durchsatz der D2D-Verbindung erhöht . Die vorliegende Arbeit stellt die oben genannten Lösungen für die D2D-Kommunikation, die den Gesamtdurchsatz in der Zelle erhöhen sollen, vor. Die Hauptbeiträge sind: i) ein positionsbasierter, hybrider Zugriffsmechanismus für die D2D-Kommunikation; ii) ein hybrider Zugriffsmechanismus für unlizenzierte Peer-to-Peer Nutzer (unlizenzierte D2D-Kommunikation); und iii) ein Algorithmus zur Link-Adaption der unlizenzierten D2D-Kommunikation. Zuerst wird in dieser Arbeit ein positions-basiertes Modell entwickelt, um den Durchsatz der D2D-Kommunikation zu maximieren, wobei unterschiedliche Zugriffsmechanismen eingesetzt werden. Im Modell werden die Regionen in der Zelle definiert, in der die D2D-Kommunikation mit der gewünschten Service-Qualität (QoS) durchgeführt werden kann. Anschließend wird ein positionsbasierter, hybrider Zugriffsmechanismus vorgestellt, der beim Einsatz für ein D2D-Paar zur Erhöhung des Gesamtumsatzes der Zelle führt. Die vorgeschlagenen Zugriffsmechanismen werden durch numerische Simulationen evaluiert. Die Ergebnisse zeigen Verbesserungen im Gesamtdurchsatz und der Anzahl der zufriedenen D2D-Kommunikationen in der Zelle. Als nächster Schritt wird kognitive Funktechnik (Cognitive Radio) in das unlizenzierte D2D-Paar integriert, wodurch ein dynamischer Zugriff auf das Funkspektrum erreicht wird. Die neu eingeführten Zugriffsmechanismen und der jeweilig erreichbare Durchsatz werden untersucht. Als Ergebnis wird ein positionsbasierter, hybrider Zugriffsmechanismus eingeführt, um die Regionen mit unlizenzierter D2D-Kommunikation zu vergrößern. Zur Evaluierung des vorgeschlagenen Zugriffsmechanismus werden numerische Simulationen eingesetzt. Die erzielten Ergebnisse weisen Verbesserungen im Durchsatz, sowohl innerhalb der Zelle, als auch in der unlizenzierten D2D-Kommunikation, nach. Als letzter Schritt wird das dynamische Verhalten der zellularen Umgebung, sowie ihrer Interaktion mit der unlizenzierten D2D-Kommunikation untersucht. Als eine mögliche Lösung wird der Einsatz künstlicher Intelligenz als eine kognitive Maschine vorgestellt, um die Funkverbindung effizient zu adaptieren. Auf Basis der Studie wird der Algorithmus „Self-Organized Link Adaptation” (SOLinA) vorgestellt, um die Funkverbindung der unlizenzierten D2D-Kommunikation autonom anzupassen und die Verbindungskonfiguration so anzupassen, dass der Systemdurchsatz erhöht wird. Evaluiert wird der vorgeschlagene Algorithmus durch Simulationen der unlizenzierten D2D-Kommumikation innerhalb einer dynamischen zellularen Umgebung. Die neuesten Simulationsergebnisse zeigen, dass SOLinA die zuvor erzielten Ergebnisse beim Durchsatz, sowohl für unterschiedliche Konstellationen der unlizenzierten D2D-Kommunikation, als auch für unterschiedliche Anforderungen an das zellulare System und für variierende Positionen der Nutzer in der Zelle übertrifft

From serendipity to sustainable Green IoT: technical, industrial and political perspective

Recently, Internet of Things (IoT) has become one of the largest electronics market for hardware production due to its fast evolving application space. However, one of the key challenges for IoT hardware is the energy efficiency as most of IoT devices/objects are expected to run on batteries for months/years without a battery replacement or on harvested energy sources. Widespread use of IoT has also led to a largescale rise in the carbon footprint. In this regard, academia, industry and policy-makers are constantly working towards new energy-efficient hardware and software solutions paving the way for an emerging area referred to as green-IoT. With the direct integration and the evolution of smart communication between physical world and computer-based systems, IoT devices are also expected to reduce the total amount of energy consumption for the Information and Communication Technologies (ICT) sector. However, in order to increase its chance of success and to help at reducing the overall energy consumption and carbon emissions a comprehensive investigation into how to achieve green-IoT is required. In this context, this paper surveys the green perspective of the IoT paradigm and aims to contribute at establishing a global approach for green-IoT environments. A comprehensive approach is presented that focuses not only on the specific solutions but also on the interaction among them, and highlights the precautions/decisions the policy makers need to take. On one side, the ongoing European projects and standardization efforts as well as industry and academia based solutions are presented and on the other side, the challenges, open issues, lessons learned and the role of policymakers towards green-IoT are discussed. The survey shows that due to many existing open issues (e.g., technical considerations, lack of standardization, security and privacy, governance and legislation, etc.) that still need to be addressed, a realistic implementation of a sustainable green-IoT environment that could be universally accepted and deployed, is still missing

5G無線通信における誤り訂正符号化方式の評価に関する研究

早大学位記番号:新8267早稲田大

AI and IoT Meet Mobile Machines

Infrastructure construction is society's cornerstone and economics' catalyst. Therefore, improving mobile machinery's efficiency and reducing their cost of use have enormous economic benefits in the vast and growing construction market. In this thesis, I envision a novel concept smart working site to increase productivity through fleet management from multiple aspects and with Artificial Intelligence (AI) and Internet of Things (IoT)

6G wireless communications networks: a comprehensive survey

The commercial fifth-generation (5G) wireless communications networks have already been deployed with the aim of providing high data rates. However, the rapid growth in the number of smart devices and the emergence of the Internet of Everything (IoE) applications, which require an ultra-reliable and low-latency communication, will result in a substantial burden on the 5G wireless networks. As such, the data rate that could be supplied by 5G networks will unlikely sustain the enormous ongoing data traffic explosion. This has motivated research into continuing to advance the existing wireless networks toward the future generation of cellular systems, known as sixth generation (6G). Therefore, it is essential to provide a prospective vision of the 6G and the key enabling technologies for realizing future networks. To this end, this paper presents a comprehensive review/survey of the future evolution of 6G networks. Specifically, the objective of the paper is to provide a comprehensive review/survey about the key enabling technologies for 6G networks, which include a discussion about the main operation principles of each technology, envisioned potential applications, current state-of-the-art research, and the related technical challenges. Overall, this paper provides useful information for industries and academic researchers and discusses the potentials for opening up new research directions