The aggregate interference distribution in cognitive radio networks is studied in a rigorous and analytical way using the popular Poisson point process model. While a number of results are available for this model for non-cognitive radio networks, cognitive radio networks present extra levels of difficulties for the analysis, mainly due to the exclusion region around the primary receiver, which are typically addressed via various ad-hoc approximations (e.g., based on the interference cumulants) or via the large-deviation analysis. Unlike the previous studies, we do not use here ad-hoc approximations but rather obtain the asymptotic interference distribution in a systematic and rigorous way, which also has a guaranteed level of accuracy at the distribution tail. This is in contrast to the large deviation analysis, which provides only the (exponential) order of scaling but not the outage probability itself. Unlike the cumulant-based analysis, our approach provides a guaranteed level of accuracy at the distribution tail. Additionally, our analysis provides a number of novel insights. In particular, we demonstrate that there is a critical transition point below which the outage probability decays only polynomially but above which it decays super-exponentially. This provides a solid analytical foundation to the earlier empirical observations in the literature and also reveals what are the typical ways outage events occur in different regimes. The analysis is further extended to include interference cancelation and fading (from a broad class of distributions). The outage probability is shown to scale down exponentially in the number of canceled nearest interferers in the below-critical region and does not change significantly in the above-critical one. The proposed asymptotic expressions are shown to be accurate in the non-asymptotic regimes as well.

Wireless networks become more and more important in modern information systems as the last mile/meter solutions, thanks to the flexibility of mobile access to facilitate Internet access anytime, anywhere. Given the limited resources, e.g., spectrum and energy supplies, to meet the ever increasing demand for wireless data services, new approaches are beckoned to enhance the spectrum and energy efficiency. We investigate this problem from three important aspects, digital modulation, clock synchronization and concurrent transmission scheduling. The contributions of this dissertation are four-fold. First, we employ the cross-layer design to explore the spatial diversity and broadcast nature of wireless links and propose a novel network modulation scheme that can superpose the information bits of different priorities into one symbol. It offers a new dimension to improve the network throughput since we can flexibly configure the transmission according to the channels among transceivers. Moreover, it is compatible with the main-stream hardware and we just need a software upgrade to implement the idea. Second, we propose modulation schemes based on hexagonal tiling, which is known to be the most compact way of two-dimensional regular tiling. In order to fully utilize the advantage of hexagonal constellation, we employ the non-binary error controlcoding since the number of constellation points of hexagonal constellation is not necessarily to be an integer power-of-two. The feasibility of these new modulation schemes is verified by the prototype system based on the software defined radio platform USRP2 and GNU Radio. Third, to facilitate a wide range of wireless communications technologies and protocols, clock synchronization among several wireless devices is a fundamental requirement. We investigated this problem by tracing to the source of clock desynchronization, which is the clock skew. However, as shown by measurement results, the clock skew is not constant and related to the working temperature. We propose a novel clock skew estimation algorithm that can leverage the temperature information to accurately estimate the clock skew. Based on the estimation results, we propose a clock synchronization scheme that can directly remove the clock skew according to the working temperature. Fourth, the traditional time-sharing based scheduling schemes usually schedule one transmission within certain area. The emerging broadband wireless devices can dynamically adjust the transmitted data rate according to the received signal to interference and noise ratio (SINR). Allowing concurrent transmissions may be more efficient, while optimal scheduling problem for concurrent transmissions is an NP-hard problem. We propose simple yet effective heuristic algorithms that can significantly improve the system throughput with moderate computational complexity. / Graduate / 0544 / yangzhe2007@gmail.com

Wireless interference networks refer to communication systems in which multiple source–destination pairs share the same transmission medium, and each source’s transmission interferes with the reception at non-intended destinations. Optimizing the transmission of each source–destination pair is interrelated with that of the other pairs, and characterizing the performance limits of these networks is a challenging task. Solving the problem of managing the interference and data communications for these networks would potentially make it possible to apply solutions to several existing and emerging communication systems. Wireless devices can carefully coordinate the use of scarce radio resources in order to deal effectively with interference and establish successful communications. In order to enable coordinated transmission, terminals must usually have a certain level of knowledge about the propagation environment; that is, channel state information (CSI). In practice, however, no CSI is a priori available at terminals (transmitters and receivers), and proper channel training mechanisms (such as pilot-based channel training and channel state feedback) should be employed to acquire CSI. This requires each terminal to share available radio resources between channel training and data transmissions. Allocating more resources for channel training leads to an accurate CSI estimation, and consequently, a precise coordination. However, it leaves fewer resources for data transmissions. This creates the need to investigate optimum resource allocation. This thesis investigates an information-theoretic approach towards the performance analysis of interference networks, and employs signal processing techniques to design transmission schemes for achieving these limits in the following scenarios. First, the smallest interference network with two single-input single-output (SISO) source–destination pairs is considered. A fixed-rate transmission is desired between each source–destination pair. Transmission schemes based on point-to-point codes are developed. The transmissions may not always attain successful communication, which means that outage events may be declared. The outage probability is quantified and the ε-outage achievable rate region is characterized. Next, a multi-user SISO interference network is studied. A pilot-assisted ergodic interference alignment (PAEIA) scheme is proposed to conduct channel training, channel state feedback, and data communications. The performance limits are evaluated, and optimum radio resource allocation problems are investigated. The analysis is extended to multi-cell wireless interference networks. A low-complexity pilot-assisted opportunistic user scheduling (PAOUS) scheme is proposed. The proposed scheme includes channel training, one-bit feedback transmission, user scheduling and data transmissions. The achievable rate region is computed, and the optimum number of cells that should be active simultaneously is determined. A multi-user MIMO interference network is also studied. Here, each source sends multiple data streams; specifically, the same number as the degrees of freedom of the network. Distributed transceiver design and power control algorithms are proposed that only require local CSI at terminals. / <p>QC 20141201</p>

With advances in hardware miniaturization and wireless communication technologies even small portable wireless devices have much communication bandwidth and computing power. These devices include smartphones, tablet computers, and personal digital assistants. Users of these devices expect to run software applications that they usually have on their desktop computers as well as the new applications that are being developed for mobile devices. Web browsing, social networking, gaming, online multimedia playing, global positioning system based navigation, and accessing emails are examples of a few popular applications. Mobile versions of thousands of desktop applications are already available in mobile application markets, and consequently, the expected operational time of smartphones is rising rapidly. At the same time, the complexity of these applications is growing in terms of computation and communication needs, and there is a growing demand for energy in smartphones. However, unlike the exponential growth in computing and communication technologies, in terms of speed and packaging density, battery technology has not kept pace with the rapidly growing energy demand of these devices. Therefore, designers are faced with the need to enhance the battery life of smartphones. Knowledge of how energy is used and lost in the system components of the devices is vital to this end. With this view, we focus on modeling and evaluating the energy performance of smartphones in this thesis. We also propose techniques for enhancing the energy efficiency and functionality of smartphones. The detailed contributions of the thesis are as follows: (i) we present a nite state machine based model to estimate the energy cost of an application running on a smartphone, and provide practical approaches to extract model parameters; (ii) the concept of energy cost pro le is introduced to assess the impact of design decisions on energy cost at an early stage of software design; (iii) a generic architecture is proposed and implemented for enhancing the capabilities of smartphones by sharing resources; (iv) we have analyzed the Internet tra c of smartphones to observe the energy saving potentials, and have studied the implications on the existing energy saving techniques; and nally, (v) we have provided a methodology to select user level test cases for performing energy cost evaluation of applications. All of our concepts and proposed methodology have been validated with extensive measurements on a real test bench. Our work contributes to both theoretical understanding of energy e ciency of software applications and practical methodologies for evaluating energy e ciency. In summary, the results of this work can be used by application developers to make implementation level decisions that affect the energy efficiency of software applications on smartphones. In addition, this work leads to the design and implementation of energy e cient smartphones.

Η ανάγκη για την έγκαιρη αντιμετώπιση καταστροφών στις μέρες μας αυξάνεται συνεχώς. Ο λόγος είναι ότι η συχνότητα των ηθελημένων καταστροφών (εμπρησμοί, τρομοκρατικές ενέργειες) έχει αυξηθεί. Ο σχεδιασμός και η παραγωγή συστημάτων ασφαλείας που θα εποπτεύουν ένα χώρο χωρίς να παραβιάζουν τα προσωπικά δεδομένα είναι ένα νέο πεδίο έρευνας. Ένα σημαντικό κομμάτι ενός τέτοιου συστήματος είναι η αναγνώριση φωτιάς μόνο με τη χρήση οπτικών αισθητήρων. Στη παρούσα διπλωματική εργασία μελετάμε διάφορες προηγούμενες τεχνικές αναγνώρισης φωτιάς και περιγράφουμε ένα επιθυμητό σύστημα. Στη συνέχεια παρουσιάζουμε τα κομμάτια του συστήματος που αναπτύξαμε και τα εργαλεία που χρησιμοποιήθηκαν, όπως το ασύρματο δίκτυο και τη βιβλιοθήκη ανοικτού λογισμικού OpenCv. Το σύστημά μας έχει στόχο να ειδοποιήσει ένα κέντρο ελέγχου για μία πιθανή εκδήλωση φωτιάς. Αυτό το πετυχαίνει επεξεργάζοντας τα δεδομένα που λαμβάνει από μία δικτυακή κάμερα και δημιουργώντας στιγμιότυπα που θα επιτρέψουν στους χειριστές του κέντρου να επαληθεύσουν την ύπαρξη της φωτιάς. Το σύστημα έχει τη δυνατότητα εκτός από την ασύρματη αποστολή των δεδομένων, να τα αποθηκεύσει τοπικά στη περίπτωση που δεν καταστεί δυνατή ή αποστολή, ώστε να ανακτηθούν αργότερα από το συνεργείο διάσωσης. / The need of prompt disaster relief actions is increasing rapidly today. The main reason is that the frequency of the intentional disasters (fires, terror acts) has increased. The design and production of unattended surveillance/alarm systems that respect the privacy and civil liberties of people is a new field of research. Fire detection using only video sensors is an integral component of such a system. In the present diploma thesis we study the various different approaches of video fire detection and we describe our systems' goals. Then we describe the main components of our system and the various tools that were used, such as the wireless network architecture and the open-source library OpenCv. The system suggested triggers an alarm and notifies a central station in the event of a fire break-out. This is carried through by processing data from an ip-camera and by creating a video with the frames that will allow the personnel at the station to verify the fire. The system also has the use of a "black box". If for any reason the communication is not possible, data is preserved until it is physically recuperated by the rescue team.

abstract: Today, many wireless networks are single-channel systems. However, as the interest in wireless services increases, the contention by nodes to occupy the medium is more intense and interference worsens. One direction with the potential to increase system throughput is multi-channel systems. Multi-channel systems have been shown to reduce collisions and increase concurrency thus producing better bandwidth usage. However, the well-known hidden- and exposed-terminal problems inherited from single-channel systems remain, and a new channel selection problem is introduced. In this dissertation, Multi-channel medium access control (MAC) protocols are proposed for mobile ad hoc networks (MANETs) for nodes equipped with a single half-duplex transceiver, using more sophisticated physical layer technologies. These include code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and diversity. CDMA increases channel reuse, while OFDMA enables communication by multiple users in parallel. There is a challenge to using each technology in MANETs, where there is no fixed infrastructure or centralized control. CDMA suffers from the near-far problem, while OFDMA requires channel synchronization to decode the signal. As a result CDMA and OFDMA are not yet widely used. Cooperative (diversity) mechanisms provide vital information to facilitate communication set-up between source-destination node pairs and help overcome limitations of physical layer technologies in MANETs. In this dissertation, the Cooperative CDMA-based Multi-channel MAC (CCM-MAC) protocol uses CDMA to enable concurrent transmissions on each channel. The Power-controlled CDMA-based Multi-channel MAC (PCC-MAC) protocol uses transmission power control at each node and mitigates collisions of control packets on the control channel by using different sizes of the spreading factor to have different processing gains for the control signals. The Cooperative Dual-access Multi-channel MAC (CDM-MAC) protocol combines the use of OFDMA and CDMA and minimizes channel interference by a resolvable balanced incomplete block design (BIBD). In each protocol, cooperating nodes help reduce the incidence of the multi-channel hidden- and exposed-terminal and help address the near-far problem of CDMA by supplying information. Simulation results show that each of the proposed protocols achieve significantly better system performance when compared to IEEE 802.11, other multi-channel protocols, and another protocol CDMA-based. / Dissertation/Thesis / Ph.D. Computer Science 2010

In this bachelor thesis, low latency wireless sensor and actuator networks are studied.In particular IEEE 802.15.4e/LLDN and IEEE 802.11g/RT-WiFi protocols. It is in-vestigated if the protocols are suitable for being used in typical industrial automationenvironments with high update frequencies of around 100 Hz. The protocols are exam-ined on a low level to shed lights on the sources of latency and followed by an analysis ofa specific configuration. It is found that LLDN is limited by low transmission rate andRT-WiFi is limited by interference with itself and other appliances. They both work wellfor update frequencies around 100 Hz.

A proposta deste trabalho foi o desenvolvimento de um protótipo composto por hardware e software de um sistema para o gerenciamento remoto de temperatura aplicado a aerogeradores de pequeno porte. O hardware microcontrolado (PIC16F877A) recebe e condiciona o sinal emitido por sensores de temperatura (termopares), executa um algoritmo e transmite a informação via rede sem fio (ZigBee) para um software instalado em um computador remoto. O software desenvolvido em linguagem de programação Delphi permite ao usuário monitorar online a temperatura e enviar sinais de comando para ligar e desligar cargas através do acionamento de relês presentes no cartão eletrônico (hardware). O sistema desenvolvido tem foco na aplicação de monitoramento de temperatura em pontos críticos dos aerogeradores de pequeno porte. O sistema permitirá inclusive que haja a intervenção do operador parando a máquina ou então acionando sistemas de refrigeração quando os limites de temperatura forem ultrapassados, visando prolongar a vida útil da máquina evitando falhas catastróficas e não catastróficas que possam inutilizar o equipamento e/ou oferecer algum tipo de risco ao meio em que se encontra. Com o objetivo de validar o desenvolvimento, o hardware implementado foi submetido a testes de validação de distância de comunicação apresentando resultado satisfatório, entretanto abaixo da especificação emitida pelo fabricante dos módulos ZigBee utilizados. O hardware e o software foram submetidos também à validação da precisão de medição da temperatura em uma máquina elétrica com características análogas aos pequenos aerogeradores onde apresentaram resultados aceitáveis para a aplicação proposta. / The proposal of this work was the development of a composed for the hardware and software of a system for the remote management of applied temperature the wind turbine of small transport. The microcontrolled hardware (PIC16F877A) receives and conditions the signal emitted for temperature sensors (thermocouples), executes an algorithm and transmits the information saw net without wire (ZigBee) for a software installed in a remote computer. The software developed in Delphi allows the user to monitor online the temperature and to send command signals to bind and disconnect loads through the drive of you reread gifts in the electronic card (the hardware). The developed system has focus in the application of monitoring of temperature in critical points of the wind turbine of small transport, also allowing that it has the intervention of the operator stopping the machine or then setting in motion refrigeration systems when the temperature limits will be exceeded, aiming at to draw out the useful life of the machine being prevented catastrophic failures and not catastrophic that can make unusable the equipment and/or offer some type of risk to the way where if it finds. With the objective to validate the development, the hardware implemented was submitted to validation tests of distance communication presenting satisfactory result, though below the specification issued by the manufacturer of ZigBee modules used. The hardware and software were also submitted to the validation of the accuracy of temperature measurement in an electric machine with features similar to small wind turbines which showed acceptable results for the proposed application.

abstract: A principal goal of this dissertation is to study wireless network design and optimization with the focus on two perspectives: 1) socially-aware mobile networking and computing; 2) security and privacy in wireless networking. Under this common theme, this dissertation can be broadly organized into three parts. The first part studies socially-aware mobile networking and computing. First, it studies random access control and power control under a social group utility maximization (SGUM) framework. The socially-aware Nash equilibria (SNEs) are derived and analyzed. Then, it studies mobile crowdsensing under an incentive mechanism that exploits social trust assisted reciprocity (STAR). The efficacy of the STAR mechanism is thoroughly investigated. Next, it studies mobile users' data usage behaviors under the impact of social services and the wireless operator's pricing. Based on a two-stage Stackelberg game formulation, the user demand equilibrium (UDE) is analyzed in Stage II and the optimal pricing strategy is developed in Stage I. Last, it studies opportunistic cooperative networking under an optimal stopping framework with two-level decision-making. For both cases with or without dedicated relays, the optimal relaying strategies are derived and analyzed. The second part studies radar sensor network coverage for physical security. First, it studies placement of bistatic radar (BR) sensor networks for barrier coverage. The optimality of line-based placement is analyzed, and the optimal placement of BRs on a line segment is characterized. Then, it studies the coverage of radar sensor networks that exploits the Doppler effect. Based on a Doppler coverage model, an efficient method is devised to characterize Doppler-covered regions and an algorithm is developed to find the minimum radar density required for Doppler coverage. The third part studies cyber security and privacy in socially-aware networking and computing. First, it studies random access control, cooperative jamming, and spectrum access under an extended SGUM framework that incorporates negative social ties. The SNEs are derived and analyzed. Then, it studies pseudonym change for personalized location privacy under the SGUM framework. The SNEs are analyzed and an efficient algorithm is developed to find an SNE with desirable properties. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2015

A proposta deste trabalho foi o desenvolvimento de um protótipo composto por hardware e software de um sistema para o gerenciamento remoto de temperatura aplicado a aerogeradores de pequeno porte. O hardware microcontrolado (PIC16F877A) recebe e condiciona o sinal emitido por sensores de temperatura (termopares), executa um algoritmo e transmite a informação via rede sem fio (ZigBee) para um software instalado em um computador remoto. O software desenvolvido em linguagem de programação Delphi permite ao usuário monitorar online a temperatura e enviar sinais de comando para ligar e desligar cargas através do acionamento de relês presentes no cartão eletrônico (hardware). O sistema desenvolvido tem foco na aplicação de monitoramento de temperatura em pontos críticos dos aerogeradores de pequeno porte. O sistema permitirá inclusive que haja a intervenção do operador parando a máquina ou então acionando sistemas de refrigeração quando os limites de temperatura forem ultrapassados, visando prolongar a vida útil da máquina evitando falhas catastróficas e não catastróficas que possam inutilizar o equipamento e/ou oferecer algum tipo de risco ao meio em que se encontra. Com o objetivo de validar o desenvolvimento, o hardware implementado foi submetido a testes de validação de distância de comunicação apresentando resultado satisfatório, entretanto abaixo da especificação emitida pelo fabricante dos módulos ZigBee utilizados. O hardware e o software foram submetidos também à validação da precisão de medição da temperatura em uma máquina elétrica com características análogas aos pequenos aerogeradores onde apresentaram resultados aceitáveis para a aplicação proposta. / The proposal of this work was the development of a composed for the hardware and software of a system for the remote management of applied temperature the wind turbine of small transport. The microcontrolled hardware (PIC16F877A) receives and conditions the signal emitted for temperature sensors (thermocouples), executes an algorithm and transmits the information saw net without wire (ZigBee) for a software installed in a remote computer. The software developed in Delphi allows the user to monitor online the temperature and to send command signals to bind and disconnect loads through the drive of you reread gifts in the electronic card (the hardware). The developed system has focus in the application of monitoring of temperature in critical points of the wind turbine of small transport, also allowing that it has the intervention of the operator stopping the machine or then setting in motion refrigeration systems when the temperature limits will be exceeded, aiming at to draw out the useful life of the machine being prevented catastrophic failures and not catastrophic that can make unusable the equipment and/or offer some type of risk to the way where if it finds. With the objective to validate the development, the hardware implemented was submitted to validation tests of distance communication presenting satisfactory result, though below the specification issued by the manufacturer of ZigBee modules used. The hardware and software were also submitted to the validation of the accuracy of temperature measurement in an electric machine with features similar to small wind turbines which showed acceptable results for the proposed application.