1,957 research outputs found
Infrastructure-less D2D Communications through Opportunistic Networks
MenciĂłn Internacional en el tĂtulo 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 networksâand cellular networks in particularâare well
engineered and have been extremely successful so far, although other paradigms should
be explored to connect people. The most promising of todayâs 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 IngenierĂa TelemĂĄtica por la Universidad Carlos III de MadridPresidente: Claudio Ettori Casetti.- Secretario: Antonio de la Oliva Delgado.- Vocal: Christoph Somme
Improving Message Dissemination in Opportunistic Networks
Data transmission has become a need in various fields, like in social networks with the diverse interaction applications, or in the scientific and engineering areas where for example the use of sensors to capture data is growing, or in emergency situations where there is the imperative need to have a communication system to coordinate rescue operations. Wireless networks have been able to solve these issues to a great extent, but what can we do when a fixed supporting infrastructure is not available or becomes inoperative because of saturation? Opportunistic wireless networks are an alternative to consider in these situations, since their operation does not depend on the existence of a telecommunications infrastructure but they provide connectivity through the organized cooperation of users.
This research thesis focuses on these types of networks and is aimed at improving the dissemination of information in opportunistic networks analyzing the main causes that influence the performance of data transmission. Opportunistic networks do not depend on a fixed topology but depend on the number and mobility of users, the type and quantity of information generated and sent, as well as the physical characteristics of the mobile devices that users have to transmit the data. The combination of these elements impacts on the duration of the contact time between mobile users, directly affecting the information delivery probability.
This thesis starts by presenting a thorough "state of the art" study where we present the most important contributions related to this area and the solutions offered for the evaluation of the opportunistic networks, such as simulation models, routing protocols, simulation tools, among others. After offering this broad background, we evaluate the consumption of the resources of the mobile devices that affect the performance of the the applications of opportunistic networks, both from the energetic and the memory point of view.
Next, we analyze the performance of opportunistic networks considering either pedestrian and vehicular environments. The studied approaches include the use of additional fixed nodes and different data transmission technologies, to improve the duration of the contact between mobile devices.
Finally, we propose a diffusion scheme to improve the performance of data transmission based on extending the duration of the contact time and the likelihood that users will collaborate in this process. This approach is complemented by the efficient management of the resources of the mobile devices.La transmisiĂłn de datos se ha convertido en una necesidad en diversos ĂĄmbitos, como en las redes sociales con sus diversas aplicaciones, o en las ĂĄreas cientĂficas y de ingenierĂa donde, por ejemplo, el uso de sensores para capturar datos estĂĄ creciendo, o en situaciones de emergencia donde impera la necesidad de tener un sistema de comunicaciĂłn para coordinar las operaciones de rescate. Las redes inalĂĄmbricas actuales han sido capaces de resolver estos problemas en gran medida, pero ÂżquĂ© podemos hacer cuando una infraestructura de soporte fija no estĂĄ disponible o estas se vuelven inoperantes debido a la saturaciĂłn de peticiones de red? Las redes inalĂĄmbricas oportunĂsticas son una alternativa a considerar en estas situaciones, ya que su funcionamiento no depende de la existencia de una infraestructura de telecomunicaciones sino que la conectividad es a travĂ©s de la cooperaciĂłn organizada de los usuarios.
Esta tesis de investigaciĂłn se centra en estos tipos de redes oportunĂsticas y tiene como objetivo mejorar la difusiĂłn de informaciĂłn analizando las principales causas que influyen en el rendimiento de la transmisiĂłn de datos. Las redes oportunĂsticas no dependen de una topologĂa fija, sino que dependen del nĂșmero y la movilidad de los usuarios, del tipo y cantidad de informaciĂłn generada y enviada, asĂ como de las caracterĂsticas fĂsicas de los dispositivos mĂłviles que los usuarios tienen para transmitir los datos. La combinaciĂłn de estos elementos influye en la duraciĂłn del tiempo de contacto entre usuarios mĂłviles, afectando directamente a la probabilidad de entrega de informaciĂłn.
Esta tesis comienza presentando un exhaustivo estudio del ``estado del arte", donde presentamos las contribuciones mĂĄs importantes relacionadas con esta ĂĄrea y las soluciones existentes para la evaluaciĂłn de las redes oportunĂsticas, tales como modelos de simulaciĂłn, protocolos de enrutamiento, herramientas de simulaciĂłn, entre otros. Tras ofrecer esta amplia compilaciĂłn de investigaciones, se evalĂșa el consumo de recursos de los dispositivos mĂłviles que afectan al rendimiento de las aplicaciones de redes oportunĂsticas, desde el punto de vista energĂ©tico asĂ como de la memoria.
A continuaciĂłn, analizamos el rendimiento de las redes oportunĂsticas considerando tanto los entornos peatonales como vehiculares. Los enfoques estudiados incluyen el uso de nodos fijos adicionales y diferentes tecnologĂas de transmisiĂłn de datos, para mejorar la duraciĂłn del contacto entre dispositivos mĂłviles.
Finalmente, proponemos un esquema de difusiĂłn para mejorar el rendimiento de la transmisiĂłn de datos basado en la extensiĂłn de la duraciĂłn del tiempo de contacto, y de la probabilidad de que los usuarios colaboren en este proceso. Este enfoque se complementa con la gestiĂłn eficiente de los recursos de los dispositivos mĂłviles.La transmissiĂł de dades s'ha convertit en una necessitat en diversos Ă mbits, com ara en les xarxes socials amb les diverses aplicacions d'interacciĂł, o en les Ă rees cientĂfiques i d'enginyeria, en les quals, per exemple, l'Ășs de sensors per a capturar dades creix en l'actualitat, o en situacions d'emergĂšncia en quĂš impera la necessitat de tenir un sistema de comunicaciĂł per a coordinar les operacions de rescat. Les xarxes sense fil han sigut capaces de resoldre aquests problemes en gran manera, perĂČ quĂš podem fer quan una infraestructura de suport fixa no estĂ disponible, o bĂ© aquestes es tornen inoperants a causa de la saturaciĂł de peticions de xarxa? Les xarxes sense fil oportunistes sĂłn una alternativa que cal considerar en aquestes situacions, ja que el funcionament d'aquestes xarxes no depĂšn de l'existĂšncia d'una infraestructura de telecomunicacions, sinĂł que la connectivitat s'hi aconsegueix a travĂ©s de la cooperaciĂł organitzada dels usuaris.
Aquesta tesi de recerca se centra en aquest tipus de xarxes, i tĂ© com a objectiu millorar la difusiĂł d'informaciĂł en xarxes oportunistes tot analitzant les principals causes que influeixen en el rendiment de la transmissiĂł de dades. Les xarxes oportunistes no depenen d'una topologia fixa, sinĂł del nombre i la mobilitat dels usuaris, del tipus i la quantitat d'informaciĂł generada i enviada, i de les caracterĂstiques fĂsiques dels dispositius mĂČbils que els usuaris tenen per a transmetre les dades. La combinaciĂł d'aquests elements influeix en la durada del temps de contacte entre usuaris mĂČbils, i afecta directament la probabilitat de lliurament d'informaciĂł.
Aquesta tesi comença amb un estudi exhaustiu de l'estat de la qĂŒestiĂł, en quĂš presentem les contribucions mĂ©s importants relacionades amb aquesta Ă rea i les solucions oferides per a l'avaluaciĂł de les xarxes oportunistes, com ara models de simulaciĂł, protocols d'encaminament o eines de simulaciĂł, entre d'altres. DesprĂ©s de mostrar aquest ampli panorama, s'avalua el consum dels recursos dels dispositius mĂČbils que afecten l'acompliment de les aplicacions de xarxes oportunistes, tant des del punt de vista energĂštic com de la memĂČria.
A continuaciĂł, analitzem l'acompliment de xarxes oportunistes considerant tant els entorns de vianants com els vehiculars. Els enfocaments estudiats inclouen l'Ășs de nodes fixos addicionals i diferents tecnologies de transmissiĂł de dades per a millorar la durada del contacte entre dispositius mĂČbils.
Finalment, proposem un esquema de difusiĂł per a millorar el rendiment de la transmissiĂł de dades basat en l'extensiĂł de la durada del temps de contacte, i de la probabilitat que els usuaris col·laboren en aquest procĂ©s. Aquest enfocament es complementa amb la gestiĂł eficient dels recursos dels dispositius mĂČbils.Herrera Tapia, J. (2017). Improving Message Dissemination in Opportunistic Networks [Tesis doctoral no publicada]. Universitat PolitĂšcnica de ValĂšncia. https://doi.org/10.4995/Thesis/10251/86129TESI
Africaâs digital solutions to tackle COVID-19
African countries are using technology in many new ways to fight the coronavirus pandemic. This report highlights some of the best digital solutions and estimates the investments required to implement the technology on a wider scale. The European Investment Bank prepared this report with the support of the United Nations Development Programme and the consulting firm BearingPoint
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
Opportunistic Data Gathering and Dissemination in Urban Scenarios
In the era of the Internet of Everything, a user with a handheld or wearable device equipped with sensing capability has become a producer as well as a consumer of
information and services. The more powerful these devices get, the more likely it is that they will generate and share content locally, leading to the presence of distributed information sources and the diminishing role of centralized servers.
As of current practice, we rely on infrastructure acting as an intermediary, providing access to the data. However, infrastructure-based connectivity might not always be available or the best alternative. Moreover, it is often the case where the data and the processes acting upon them are of local scopus. Answers to a query about a nearby object, an information source, a process, an experience, an ability, etc. could be answered locally without reliance on infrastructure-based platforms. The data might have temporal validity limited to or bounded to a geographical
area and/or the social context where the user is immersed in.
In this envisioned scenario users could interact locally without the need for a central authority, hence, the claim of an infrastructure-less, provider-less platform. The data is owned by the users and consulted locally as opposed to the current approach of making them available globally
and stay on forever. From a technical viewpoint, this network resembles a Delay/Disruption Tolerant Network where consumers and producers might be spatially and temporally decoupled exchanging information with each other in an adhoc fashion.
To this end, we propose some novel data gathering and dissemination strategies for use in urban-wide environments which do not rely on strict infrastructure mediation. While preserving the general aspects of our study and without loss of generality, we focus our attention toward practical applicative scenarios which help us capture the characteristics of opportunistic communication networks
Africaâs digital solutions to tackle COVID-19
African countries are using technology in many new ways to fight the coronavirus pandemic. This report highlights some of the best digital solutions and estimates the investments required to implement the technology on a wider scale. The European Investment Bank prepared this report with the support of the United Nations Development Programme and the consulting firm BearingPoint
Controlling and constraining the participation of the hepatitis C-affected community in Australia: A critical discourse analysis of the first national hepatitis C strategy and selected news media texts
The construction of texts that place hepatitis C-positive persons at social risk (Candlin, 1989, p. ix), informs this study of the ways in which public health policy makers and journalists in Australia communicate about hepatitis C. The institutions of public health and the news media form part of the cultural context within which persons construct their illness narratives. The privileged perspectives and framing of public health policy and news media discourses; the discursive practices associated with the institutions of public health and the media around hepatitis C and hepatitis C-positive persons, the âobjectsâ of knowledge (Foucault, 1969/2002, p. 81); and the subject and social positions available to hepatitis C-positive people and spokespersons of non-government organisations (NGOs) representing the hepatitis C-affected community are examined. The place afforded the voices of individuals living with hepatitis C in these forums to discuss topics of public concern is considered
Geographies of HIV/AIDS in Bangladesh: Vunerability, Stigma and Place.
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Effective and Efficient Communication and Collaboration in Participatory Environments
Participatory environments pose significant challenges to deploying real applications. This dissertation investigates exploitation of opportunistic contacts to enable effective and efficient data transfers in challenged participatory environments.
There are three main contributions in this dissertation:
1. A novel scheme for predicting contact volume during an opportunistic contact (PCV);
2. A method for computing paths with combined optimal stability and capacity (COSC) in opportunistic networks; and
3. An algorithm for mobility and orientation estimation in mobile environments (MOEME).
The proposed novel scheme called PCV predicts contact volume in soft real-time. The scheme employs initial position and velocity vectors of nodes along with the data rate profile of the environment. PCV enables efficient and reliable data transfers between opportunistically meeting nodes.
The scheme that exploits capacity and path stability of opportunistic networks is based on PCV for estimating individual link costs on a path. The total path cost is merged with a stability cost to strike a tradeoff for maximizing data transfers in the entire participatory environment. A polynomial time dynamic programming algorithm is proposed to compute paths of optimum cost.
We propose another novel scheme for Real-time Mobility and Orientation Estimation for Mobile Environments (MOEME), as prediction of user movement paves way for efficient data transfers, resource allocation and event scheduling in participatory environments. MOEME employs the concept of temporal distances and uses logistic regression to make real time estimations about user movement. MOEME relies only on opportunistic message exchange and is fully distributed, scalable, and requires neither a central infrastructure nor Global Positioning System.
Indeed, accurate prediction of contact volume, path capacity and stability and user movement can improve performance of deployments. However, existing schemes for such estimations make use of preconceived patterns or contact time distributions that may not be applicable in uncertain environments. Such patterns may not exist, or are difficult to recognize in soft-real time, in open environments such as parks, malls, or streets
- âŠ