Infrastructure-less D2D Communications through Opportunistic Networks

Mención Internacional en el título de doctorIn recent years, we have experienced several social media blackouts, which have shown how much our daily experiences depend on high-quality communication services. Blackouts have occurred because of technical problems, natural disasters, hacker attacks or even due to deliberate censorship actions undertaken by governments. In all cases, the spontaneous reaction of people consisted in finding alternative channels and media so as to reach out to their contacts and partake their experiences. Thus, it has clearly emerged that infrastructured networks—and cellular networks in particular—are well engineered and have been extremely successful so far, although other paradigms should be explored to connect people. The most promising of today’s alternative paradigms is Device-to-Device (D2D) because it allows for building networks almost freely, and because 5G standards are (for the first time) seriously addressing the possibility of using D2D communications. In this dissertation I look at opportunistic D2D networking, possibly operating in an infrastructure-less environment, and I investigate several schemes through modeling and simulation, deriving metrics that characterize their performance. In particular, I consider variations of the Floating Content (FC) paradigm, that was previously proposed in the technical literature. Using FC, it is possible to probabilistically store information over a given restricted local area of interest, by opportunistically spreading it to mobile users while in the area. In more detail, a piece of information which is injected in the area by delivering it to one or more of the mobile users, is opportunistically exchanged among mobile users whenever they come in proximity of one another, progressively reaching most (ideally all) users in the area and thus making the information dwell in the area of interest, like in a sort of distributed storage. While previous works on FC almost exclusively concentrated on the communication component, in this dissertation I look at the storage and computing components of FC, as well as its capability of transferring information from one area of interest to another. I first present background work, including a brief review of my Master Thesis activity, devoted to the design, implementation and validation of a smartphone opportunistic information sharing application. The goal of the app was to collect experimental data that permitted a detailed analysis of the occurring events, and a careful assessment of the performance of opportunistic information sharing services. Through experiments, I showed that many key assumptions commonly adopted in analytical and simulation works do not hold with current technologies. I also showed that the high density of devices and the enforcement of long transmission ranges for links at the edge might counter-intuitively impair performance. The insight obtained during my Master Thesis work was extremely useful to devise smart operating procedures for the opportunistic D2D communications considered in this dissertation. In the core of this dissertation, initially I propose and study a set of schemes to explore and combine different information dissemination paradigms along with real users mobility and predictions focused on the smart diffusion of content over disjoint areas of interest. To analyze the viability of such schemes, I have implemented a Python simulator to evaluate the average availability and lifetime of a piece of information, as well as storage usage and network utilization metrics. Comparing the performance of these predictive schemes with state-of-the-art approaches, results demonstrate the need for smart usage of communication opportunities and storage. The proposed algorithms allow for an important reduction in network activity by decreasing the number of data exchanges by up to 92%, requiring the use of up to 50% less of on-device storage, while guaranteeing the dissemination of information with performance similar to legacy epidemic dissemination protocols. In a second step, I have worked on the analysis of the storage capacity of probabilistic distributed storage systems, developing a simple yet powerful information theoretical analysis based on a mean field model of opportunistic information exchange. I have also extended the previous simulator to compare the numerical results generated by the analytical model to the predictions of realistic simulations under different setups, showing in this way the accuracy of the analytical approach, and characterizing the properties of the system storage capacity. I conclude from analysis and simulated results that when the density of contents seeded in a floating system is larger than the maximum amount which can be sustained by the system in steady state, the mean content availability decreases, and the stored information saturates due to the effects of resource contention. With the presence of static nodes, in a system with infinite host memory and at the mean field limit, there is no upper bound to the amount of injected contents which a floating system can sustain. However, as with no static nodes, by increasing the injected information, the amount of stored information eventually reaches a saturation value which corresponds to the injected information at which the mean amount of time spent exchanging content during a contact is equal to the mean duration of a contact. As a final step of my dissertation, I have also explored by simulation the computing and learning capabilities of an infrastructure-less opportunistic communication, storage and computing system, considering an environment that hosts a distributed Machine Learning (ML) paradigm that uses observations collected in the area over which the FC system operates to infer properties of the area. Results show that the ML system can operate in two regimes, depending on the load of the FC scheme. At low FC load, the ML system in each node operates on observations collected by all users and opportunistically shared among nodes. At high FC load, especially when the data to be opportunistically exchanged becomes too large to be transmitted during the average contact time between nodes, the ML system can only exploit the observations endogenous to each user, which are much less numerous. As a result, I conclude that such setups are adequate to support general instances of distributed ML algorithms with continuous learning, only under the condition of low to medium loads of the FC system. While the load of the FC system induces a sort of phase transition on the ML system performance, the effect of computing load is more progressive. When the computing capacity is not sufficient to train all observations, some will be skipped, and performance progressively declines. In summary, with respect to traditional studies of the FC opportunistic information diffusion paradigm, which only look at the communication component over one area of interest, I have considered three types of extensions by looking at the performance of FC: over several disjoint areas of interest; in terms of information storage capacity; in terms of computing capacity that supports distributed learning. The three topics are treated respectively in Chapters 3 to 5.This work has been supported by IMDEA Networks InstitutePrograma de Doctorado en Ingeniería Telemática por la Universidad Carlos III de MadridPresidente: Claudio Ettori Casetti.- Secretario: Antonio de la Oliva Delgado.- Vocal: Christoph Somme

Utility of behavioural science in landscape architecture: investigating the application of environment-behaviour theory and its research methods to fit the spatial agenda of design

This thesis attempts to address the behavioural science /design `applicability gap' problem currently concerning professional academics and researchers in landscape architecture and related disciplines. Building on research carried out by others, it attempts to gain further insight into the nature of the problem, how the gap specifically relates to landscape design, how it manifests itself in the design process, and how the problem might realistically be addressed. It is argued that in order to address the gap problem in landscape architecture, it is also necessary to address the wider problem of the lack of communication and understanding between research and design spheres. Therefore, the study is conducted from a combined research/design perspective. A critical review of the literature combined with project driven reflection -in- action analysis establishes a lack of compatibility of environment- behaviour theory, and its research methods, with the landscape designer's spatial approach. It is argued that there is a need for theory- building to facilitate the practical application of integrated spatial -behaviour analysis. As a result, a framework of spatial/behavioural compatible theories and concepts, and a set of practical tools and techniques, are conceptualised, and their application explored, for site survey analysis. The utility of the approach is demonstrated for embodying user needs evaluation within the design process and for providing a method for contextualising research. Finally, a shift in thinking is envisaged in which research and design approaches are reconciled

Furtive Encryption: Power, Trusts, and the Constitutional Cost of Collective Surveillance

Recent revelations of heretofore secret U.S. government surveillance programs have sparked national conversations about their constitutionality and the delicate balance between security and civil liberties in a constitutional democracy. Among the revealed policies asserted by the National Security Agency (NSA) is a provision found in the “minimization procedures” required under section 702 of the Foreign Intelligence Surveillance Act of 1978. This provision allows the NSA to collect and keep indefinitely any encrypted information collected from domestic communications—including the communications of U.S. citizens. That is, according to the U.S. government, the mere fact that a U.S. citizen has encrypted her electronic communications is enough to give the NSA the right to store that data until it is able to decrypt or decode it. Through this provision, the NSA is automatically treating all electronic communications from U.S. citizens that are hidden or obscured through encryption—for whatever reason—as suspicious, a direct descendant of the “nothing-to-hide” family of privacy minimization arguments. The ubiquity of electronic communication in the United States and elsewhere has led to the widespread use of encryption, the vast majority of it for innocuous purposes. This Article argues that the mere encryption by individuals of their electronic communications is not alone a basis for individualized suspicion. Moreover, this Article asserts that the NSA’s policy amounts to a suspicionless search and seizure. This program is therefore in direct conflict with the fundamental principles underlying the Fourth Amendment, specifically the protection of individuals from unwarranted government power and the establishment of the reciprocal trust between citizen and government that is necessary for a healthy democracy

Thinking outside the boxes: barriers to inclusion for persons with physical impairments in higher education

Since passage of the Americans with Disabilities Act in 1990 the participation rate of students with physical impairments in higher education has remained static or declined. Though a number of potential issues have been identified most research tends to focus on classrooms, building interiors, and technology rather than exterior landscapes and fiscal policies that treat all students the same way. Most studies have also lacked theoretical rigor, relying instead on models of disability and statistics to explain their data, rather than on an extensive body of community based, multidisciplinary studies employing urban theories of space and place. Using space and place theory as a template and critical discourse analysis to examine data collected from two comparable mid-sized Washington State public universities the author has attempted to expose some of the underlying dominant and minority discourses concerning exterior barriers to inclusion for persons with physical impairments in higher education by placing these issues in historical context while fully encasing them within urban anthropology and contemporary urban studies of architecture, geography, sociology, and disability

Photography in the Middle: Dispatches on Media Ecologies and Aesthetics

It’s easy to forget there’s a war on when the front line is everywhere encrypted in plain sight. Gathered in this book’s several chapters are dispatches on the role of photography in a War Universe, a space and time in which photographers such as Hilla Becher, Don McCullin and Eadweard Muybridge exist only insofar as they are a mark of possession, in the sway of larger forces. These photographers are conceptual personae that collectively fabulate a different kind of photography, a paraphotography in which the camera produces negative abyssal flashes or ‘endarkenment.’ In his Vietnam War memoir, Dispatches, Michael Herr imagines a ‘dropped camera’ receiving ‘jumping and falling’ images, images which capture the weird indivisibility of medium and mediated in a time of war. The movies and the war, the photographs and the torn bodies, fused and exchanged. Reporting from the chaos at the middle of things, Herr invokes a kind of writing attuned to this experience. Photography in the Middle, eschewing a high theoretical mode, seeks to exploit the bag of tricks that is the dispatch. The dispatch makes no grand statement about the progress of the war. Cultivating the most perverse implications of its sources, it tries to express what the daily briefing never can. Ports of entry in the script we’re given, odd and hasty little glyphs, unhelpful rips in the cover story, dispatches are futile, dark intuitions, an expeditious inefficacy. They are bleak but necessary responses to an indifferent world in which any action whatever has little noticeable effect

The End of Traffic and the Future of Access: A Roadmap to the New Transport Landscape

In most industrialized countries, car travel per person has peaked and the automobile regime is showing considering signs of instability. As cities across the globe venture to find the best ways to allow people to get around amidst technological and other changes, many forces are taking hold — all of which suggest a new transport landscape. Our roadmap describes why this landscape is taking shape and prescribes policies informed by contextual awareness, clear thinking, and flexibility

Black Boxes : Airport Space, Liminal Mechanisms, and Systems of Autobiography

Treating the first-person experience of airport space as an ethnographic tool, this thesis examines spatial perception and its breakdown in multiple examples of imagined and real twentieth century spatial constructs. First, it considers examples of failed or redundant mechanisms which function as liminal constructs, either through their presence as physical objects or through use as tools with which to perceive liminal spaces. It emphasizes their function as points of access for narrative and delineates their status as examples of failure in relation to Bruno Latour's use of the term "black box," appropriated from the world of air crash investigation, and to Walter Benjamin's collection and juxtaposition of research in Tbe Arcades Project. Second, it explores the type and sequence of spaces encountered by a traveller in a large contemporary international airport, and those behaviours that are inscribed and prescribed upon people and mechanisms therein. It critiques Marc Auge' s ideas of the "non-place" through explorations of a distinctly airport-specific culture and possible deconstructions of airport space by passenger use and mechanical and architectural functions. Finally, it relates these to narrative space through an examination and practice of systemic approaches to autobiography in works by Georges Perec, Michel Leiris, and Raymond Queneau. It uses the first-person construction of a narrative of airport space-a first-person "silent reading" of public space-to construct a system of research through which twentieth-century liminal space may be inhabited and critiqued from within and on its own terms. Thus the constraint and potential offered by these diverse liminal spaces are deconstructed in terms of the personal narrative, and through use of airport space demonstrate an inhabiting of research through an innovative and revealing method

Novel Buildings: Architectural and Narrative Form in Victorian Fiction

This dissertation, “Novel Buildings: Architectural and Narrative Form in Victorian Fiction,” offers an interdisciplinary study of the relationship between the economic and social histories of built space and the Victorian literary imagination. At its most fundamental level, it claims that the spaces we inhabit shape the stories we tell. Reading Victorian literature through the architectural archive of the period, it argues that the nineteenth century’s rapidly evolving built environment resulted in a new set of narrative possibilities and laid the foundations for authorial innovations in genre, style, and form. Organized taxonomically around four architectural types reinvented in the nineteenth century—courthouses, hotels, theaters, and hospitals—my work examines novels that co-opt realism’s thick descriptions of these spaces for political and aesthetic ends. Drawing upon contemporary approaches to literary studies, including affect studies and environmental studies, these readings are connected by a consideration of the performative and intersubjective nature of public space. Parallel to my project’s critical engagement with material culture, human geography, and spatial embodiment is its attentiveness to the imbrication of literary and physical forms, thus taking up Victorian studies’ recent turn to new formalisms and its efforts at grounding the aesthetic within the everyday. My dissertation’s historical arc extends from the end of the eighteenth century through the end of the nineteenth, and its geographic trajectory traces a course from England’s agricultural and manufacturing provinces, through its urban metropole, to its continental and colonial outposts. Building upon previous literary studies of domestic, carceral, and commercial architecture, my project expands the critical archive to include a set of relatively understudied public spaces whose cultural significance remains profound even today. Moreover, it contributes to Victorian studies’—and literary studies’ in general—recent reinvestment in formalism(s) as it demonstrates the relationship between the various, intersecting, forms that govern and compose built environments, social relations, and literature. Beyond the portability of my methodology to additional architectural forms and/or other literary fields, my project also provides new humanistic avenues of inquiry in the study of urban development and it shifts the ways in which we read and understand representations of space