No / Enabling D2D communications over LTE-A networks can provide many benefits in terms of throughput, energy consumption, traffic load, and so on. It also enables new commercial services such as location-based advertising. For these reasons, D2D communications has become a hot topic in both the academic and industrial communities. However, many research works are focused on node discovery, radio resource management, and other aspects, while the issue of security is less addressed. In this article, we intend to provide an overview of the security architecture, threads, and requirements. Based on these requirements, we propose several potential solutions by reusing the existing security mechanisms. Promising topics related to secure D2D communications for future research are also discussed.

Device-to-device communication has been suggested as a complement to traditional cellular networks as a means of offloading cellular traffic. In this thesis we explore a solution for device-to-device communication based on opportunistic content distribution in a content-centric network. Communication opportunities arise as mobile nodes roam around in an area and occasionally enter in direct communication range with one another. We consider a node to be a pedestrian equipped with a mobile device and explore the properties of opportunistic communication in the context of content dissemination in urban areas. The contributions of this thesis lie in three areas. We first study human mobility as one of the main enablers of opportunistic communication. We introduce traces collected from a realistic pedestrian mobility simulator and demonstrate that the performance of opportunistic networks is not very sensitive to the accurate estimation of the probability distributions of mobility parameters. However, capturing the space in which mobility occurs may be of high importance. Secondly, we design and implement a middleware for opportunistic content-centric networking, and we evaluate it via a small-scale testbed, as well as through extensive simulations. We conclude that energy-saving mechanisms should be part of the middleware design, while caching should be considered only as an add-on feature. Thirdly, we present and evaluate three different energy-saving mechanisms in the context of opportunistic networking: a dual-radio architecture, an asynchronous duty-cycling scheme, and an energy-aware algorithm which takes into account node selfishness. We evaluate our proposals analytically and via simulations. We demonstrate that when a critical mass of participants is available, the performance of the opportunistic network is comparable to downloading contents directly via the cellular network in terms of energy consumption while offloading large traffic volumes from the operator. / <p>QC 20151120</p>

Wireless communication systems are growing at an unprecedented pace, making the wireless spectrum at a premium, especially as billions of new Internet-of-Things (IoT) devices worldwide are demanding wireless connections. To accommodate the ever-growing spectrum demand, a promising solution is Non-Orthogonal Multiple Access (NOMA) that enables two users to communicate with the same spectrum resource at the same time, while decoding the two-user superimposed signal at the receiver. By doing this, the previously detrimental wireless interference caused by two concurrent transmitters becomes decodable at the receiver, potential for higher utilization of the wireless spectrum. Existing NOMA technologies, however, rely on strict power control to sequentially decode the two-user superimposed signal, which is infeasible for many IoT devices that are heterogeneous and often low-cost. In contrast, in this dissertation, we propose new NOMA schemes that are designed for wireless communication systems and can decode the two-user superimposed signals without power control. This dissertation makes four major contributions. First, it presents the first design to implement dynamic signal offsets tracking and reacting schemes to detect and decode two-user superimposed signals, robust against hardware imperfections and feasible for heterogeneous IoT devices. Second, by investigating the relationship between the channel condition and the bit-error-rate (BER) in decoding superimposed signals, we design a reliable NOMA scheme to combat dynamic channel conditions that are inevitable in many practical scenarios and may cause severe decoding errors. Third, considering the wireless communication systems in mobile scenarios, mobility is a vital feature of many applications but can cause severe signal variations and make the hardware offsets harder to predict, resulting in an unreliable decoding performance. To address this, we develop a diversity transmission and smart combining scheme to achieve high reliable decoding performance. Finally, we combine rotation coding to transmit and decode the superimposed signal to achieve both high spectrum efficiency and high reliability performance. To demonstrate our contributions, we derive the theoretical relationship of the BER under different practical settings, validate the performance with simulations, and conduct experiments using software-defined radio based platforms with static indoor, outdoor scenarios and mobile scenarios. The experimental results demonstrate that, compared with the state-of-the-art methods, our schemes can achieve higher reliability and spectrum efficiency in decoding the superimposed signal for wireless communication systems without power control. / Graduate

Various techniques are used in the process of software development. The requirements of the system being designed and the constraints dictate the selection of a particular method to be used. This thesis attempts to explain the various types of development techniques available to software designers and programmers. It places specific emphasis on the Object Oriented style of design that is presently widely used in all areas of industry. Object Oriented Programming (OOP) involves a number of new concepts that make software design and development more modular. The actual problem is broken down into a number of smaller components and the functionality of each component is coded separately. These pieces of code are then integrated to form the final application. All the concepts that make this type of programming possible are explained. The thesis presents a detailed account of the development process of a system used to make measurements on polyurethane pads that are used in the Chemical Mechanical Planarization (CMP) process. The setup uses a combination of a number of instruments to provide excitation to the pad and measure its response. A computer controls all these instruments using a single application. Microsoft Visual C++ was used to develop this application. It makes extensive use of a Graphic User Interface (GUI), Microsoft Foundation Classes (MFC) and driver libraries from instrument manufacturers in order to present a user-friendly interface to the operator. System Integration, which is the technique used to make the instruments involved interact with the software is explained. The application involves the use of a number of C++ classes and dialog boxes. Each of these is explained along with the underlying algorithms.

L’informatique ubiquitaire est graduellement devenue une réalité, nous utilisons divers dispositifs pour travailler et s’amuser (l’ordinateur, le portable, le smartphone). Au-delà des dispositifs personnels, les citoyens obtiennent des informations par les écrans publics qui sont présents partout dans les villes: l’abribus, l’aéroport, le centre commercial, etc. Il semble que la vision de l’informatique ubiquitaire est plus proche, cependant, l’avenir décrit par Mark Weiser est encore loin: «les technologies les plus profondes sont celles qui disparaissent». Actuellement les appareils électroniques ne sont pas assez intelligents et bien intégrés dans le contexte d’une ville. La ville intelligente (smart city) est un concept émergent pour construire une ville utilisant les technologies de l’information et de la communication (TIC). Ce concept propose d’améliorer la qualité de la vie et d’augmenter l’efficacité des activités dans une ville par les TIC. Il aussi met l’accent sur les savoir-faire des citoyens pour la construction des villes. La ville intelligente est en effet un système ubiquitaire large qui comprend différent systèmes (le système de gestion trafic, le système de transport public, le système de distribution de l’énergie, etc.). Les écrans publics construisent l’une des plus importants systèmes dans une ville. Cependant, ils ne sont utilisés que pour afficher de l’information, ils sont aveugles aux utilisateurs ainsi qu’à leurs dispositifs personnels. Dans cette thèse, nous proposons de construire des écrans publics intelligents basés sur l’interaction proxémique. L’interaction proxémique est inspirée par le terme venant de la psychologie «Proxémique». La Proxémique désigne les espaces virtuels autour des êtres humains pendant la communication. Les espaces sont différents selon la culture, les lieux où l’interaction se déroule. La Proxémique a été introduite à l’interaction homme machine par S. Greenberg en 2011 et il a créé le terme d’interaction proxémique. L’interaction proxémique étudie l’interaction en fonction de la relation spatiale entre les objets. Un écran proxémique peut connaître la distance, la position, l’identité et le mouvement de l’utilisateur. Ces dimensions proxémiques sont mesurées par l’écran comme les signaux de l’interaction implicite. Par ailleurs, il peut détecter les dispositifs mobiles des utilisateurs: il peut distribuer et échanger de l’information avec les dispositifs de l’environnement. Par rapport à un écran traditionnel, un écran proxémique offre des contenus plus personnalisés et ainsi répond aux besoins immédiats des utilisateurs. Ces avantages permettent à un écran public de bien s’adapter aux exigences de la ville intelligente. Notre objectif est d’étudier la façon de relever les défis d’un écran public dans une ville intelligente par l’interaction proxémique. Pour atteindre cet objectif, nous étudions les dimensions de l’interaction proxémique, et puis nous concevons un prototype d’écran proxémique grâce à différents capteurs: Kinect, Leapmotion et Webcam. Ce prototype supporte l’interaction implicite et explicite des utilisateurs pour fournir un contenu plus personnalisé aux utilisateurs, ainsi que des interactions naturelles. En outre, nous avons développé une boîte à outils pour la migration des données entre l’écran public et les appareils mobiles personnels. Avec cet outil, l’utilisateur peut télécharger des ressources à partir de l’écran, et l’écran deviendra un terminal pour recueillir les connaissances des citoyens pour la ville intelligente. Nous discutons les applications potentielles de ce prototype dans la ville intelligente, et nous proposons une application expérimentale qui est un panneau d’affichage proxémique des vols dans un aéroport. Basé sur cette application, nous avons réalisé des études utilisateurs systématiques dans notre laboratoire pour vérifier si l’interaction proxémique peut vraiment améliorer les performances d’un écran public. / Ubiquitous computing is gradually coming into reality, people use various digital devices (personal computer, laptop, tablet and smartphone) in order to study, work, entertain and communicate with each other. A city is actually a ubiquitous society, citizens get practical information from digital public displays that are installed everywhere in a city: bus station, railway station, airport or commercial center, etc. It seems that we are closing to the vision of ubiquitous computing, however, it’s still far from the vision what Mark Weiser described: the most profound technologies are those that disappear, they weave themselves into the fabric of everyday life until they are indistinguishable from it. That means in nowadays the widespread digital devices are still not intelligent enough and not well integrated, this issue is especially serious under a context of city than for personal usage condition.Smart city is a modern concept of city that seeks to improve the efficiency and quality of life by the information and communication technologies (ICTs), it as well emphasizes the importance of citizens’ knowledge for the wise management of city. The ICTs of a smart city constructs a large scale ubiquitous system, including traffic control systems, public transportation system, energy control systems, etc. In all the systems, digital public displays are one of the most important viewports that connect citizens with city. However, the public display today is only used as a screen to display information, it’s blind to the presence of users and ambient devices, these result in low efficiency of interactions, and make a city unable to take use of citizen knowledge.In this dissertation, we build an intelligent public display by the theory of proxemic interaction. Proxemic interaction is spatial related interaction patterns inspired by the psychological term: Proxemics, it studies the spatial -related interaction human to device and device to device. A proxemic interactive public display means that it is aware of user’s presence, position, movement, identity and other user related attributes, and takes these attributes as implicit inputs for interactions. Besides, it can sense ambient mobile devices and act as a hub for local deices information flows. Compared with traditional public display, proxemic interactive display can provide specific users with more personal related and instant - need information rather than provide general information to all users. That means to make displays sense users instead of making users explore displays exhaustively. These advantages make a proxemic display more adapt to the prospect of smart city.Our object is to study how to address the challenges of public display in a smart city by proxemic interaction. Towards this object, we study the dimensions of proxemic interaction, and build a prototype of proxemic interactive projected display with Kinect, Leap motion and web camera. This prototype supports implicit and explicit interaction of users to provide more personalized contents to users, as well as natural interactions. Furthermore, we developed a toolkit for data migration between public display and personal mobile devices, so that public display becomes aware of ambient users’ devices, users can download resources from public displays freely, while public displays can be as a terminal to collect knowledge of citizens for smart city.We discuss the potential applications of this prototype under smart city, and build an experimental application of proxemic airport flight information board. Based on this experimental application, we organized a systematic laboratory user study to validate whether proxemic interaction can really improve the performance of public displays

Multi-tier cellular networks have led to a paradigm shift in the deployment of base stations (BSs) where macrocell BSs are overlaid with smaller and lower power BSs such as microcells, picocells, and femtocells. Stochastic geometry has been proven to be an effective tool to capture such heterogeneity and uncertainties in deployment of cellular BSs. In stochastic geometry, random spatial models are used to model multi-tier cellular networks where the locations of BSs is each tier is assumed to be drawn from a point process with the appropriate spatial density. This thesis proposes stochastic geometry-based approaches to analyze, model, and optimize multi-tier cellular networks under several setups and technologies. First, I propose a novel location-aware cross-tier cooperation scheme that aim at improving the performance of users with low signal-to-interference-plus-noise ratio (SINR). Second, I study the performance of cognitive device-to-device (D2D) communication in multi-channel downlink-uplink cellular network with energy harvesting. For the coexistence between cellular and D2D transmissions, I propose a spectrum access policy for cellular BSs to avoid using D2D channels when possible. Third, I investigate the feasibility of energy harvesting from ambient RF interference in multi-tier uplink cellular networks. For this setup, I capture randomness in the network topology and the battery dynamics. Fourth, I extend multi-tier uplink cellular networks to consider the case when users do not necessarily associate with the nearest BS (i.e., flexible cell association). Finally, I compare between different cell association criteria including coupled and decoupled cell association for uplink and downlink transmissions in multi-tier full-duplex cellular networks. For all network setups, I use stochastic geometry to derive simple and closed-form expressions to evaluate the performance in terms of several metrics, e.g., outage probability, mean rate, transmission probability, success probability, and load per BS. I also highlight main tradeoffs in different networks and provide guidelines to optimize different performance metrics by carefully tuning fundamental network design parameters. / February 2017

Title: Multi-platform Multiplayer RPG Game A multi-platform game, which would be able to run on various devices with Windows 8.1 and Windows Phone 8.1 systems, was created in this work. It was supposed to be a universal game client executable on desktop PCs, notebooks, tablets or mobile phones. The game was supposed to be role-playing game (RPG) with focus on turn-based action combat. In this work, a 3D scene renderer was written which supports rendering simple scenes with objects and animated characters. A cross-device communication library based on bluetooth technology was implemented in this project as well. This communication library allows two game clients running on two different types of devices to communicate with each other. Then a server-client communication library was created. This library was then used to implement a game server which offers online gaming feature.

Supporting emerging mobile applications in densely populated environments requires connecting mobile users and their devices with the surrounding digital landscape. Specifically, the volume of digitally-available data in such computing spaces presents an imminent need for expressive mechanisms that enable humans and applications to share and search for relevant information within their digitally accessible physical surroundings. Device-to-device communications will play a critical role in facilitating transparent access to proximate digital resources. A wide variety of approaches exist that support device-to-device dissemination and query-driven data access. Very few, however, capitalize on the contextual history of the shared data itself to distribute additional data or to guide queries. This dissertation presents Gander, an application substrate and mobile middleware designed to ease the burden associated with creating applications that require support for sharing and searching of hyper-localized data in situ. Gander employs a novel trajectory-driven model of spatiotemporal provenance that enriches shared data with its contextual history -- annotations that capture data's geospatial and causal history across a lifetime of device-to-device propagation. We demonstrate the value of spatiotemporal data provenance as both a tool for improving ad hoc routing performance and for driving complex application behavior. This dissertation discusses the design and implementation of Gander's middleware model, which abstracts away tedious implementation details by enabling developers to write high-level rules that govern when, where, and how data is distributed and to execute expressive queries across proximate digital resources. We evaluate Gander within several simulated large-scale environments and one real-world deployment on the UT Austin campus. The goal of this research is to provide formal constructs realized within a software framework that ease the software engineering challenges encountered during the design and deployment of several applications in emerging mobile environments. / text

Title: Multi-platform Multiplayer RPG Game A multi-platform game, which would be able to run on various devices with Windows 8.1 and Windows Phone 8.1 systems, was created in this work. It was supposed to be a universal game client executable on desktop PCs, notebooks, tablets or mobile phones. The game was supposed to be role-playing game (RPG) with focus on turn-based action combat. In this work, a 3D game engine was written which supports rendering simple scenes with objects and animated characters. The engine was developed using DirectX. The engine was written in .NET C# using SharpDX library. A cross-device communication framework based on bluetooth technology was implemented in this project as well. This communication framework allows two game clients running on two different devices to communicate with each other.

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the 'wrap around' technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission.