Efficient opportunistic routing in dense mobile networks

The usage of smartphones is nowadays ubiquitous. Their simultaneous support for longand short-range communication has enabled the deployment of opportunistic, device-todevice networks, which exploit human mobility to enable and facilitate communication and content exchange among peer devices. Devices connect to each other without human intervention, potentially with the assistance of the cellular network provider. The underlying network topology constantly changes, depending on the mobility patterns of the participating mobile devices. Mobile devices support various technologies for discovering their location; GPS is very accurate but it works only outdoors and is power-hungry, whereas location discovery based on nearby announced SSIDs and/or the current cell ID is less accurate but power-friendly. Indoor localisation is much more challenging; approaches that are based on inertial sensors and dead reckoning, along with deployed beacons and pre-calculated signal strength maps have been proposed. In this thesis, we develop GeoHawk, a routing protocol for dense mobile networks that support opportunistic communication and content dissemination among mobile devices in crowded events. The driving use case has been the Grand Mosque, the largest mosque in the world located at the heart of the city of Makkah in Saudi Arabia. During the Ramadan and Hajj, viii the Grand Mosque can get extremely crowded, with anticipated number of visitors close to 2.5 million, after the current expansion work is completed. The proposed protocol incorporates a novel distributed localisation technique that can be used in conjunction with the protocol, when GPS is not available. GeoHawk deals with the very high density of users/devices by heavily aggregating routing information using Bloom filters. Identifiers of mobile devices that reside within specific geographical regions are disseminated in the network in the form of Bloom filters. Said geographical regions are dynamically created and destroyed; their size evolves to reflect the uncertainty in the topology, due to mobility and potential inaccuracies of the underlying location estimation mechanism. Bloom filters are also decayed to reflect information ageing. Devices exchange routing information with their neighbours and announce aggregated information (i.e. Bloom filters) in messages that propagate towards specific directions and reach distant areas of the opportunistic network. Data is then disseminated (and replicated through a simple but efficient ticketing mechanism) towards directions where the information about the existence of the destination node is stronger. Upon reaching the best-known region for the destination node, a message is either flooded, if the belief that the node resides in the region is strong (as indicated by a belief threshold), or, in the opposite case, redirected to a randomly selected region. The distributed localisation algorithm is a novel synthesis of existing techniques, including Pedestrian Dead Reckoning, estimated location sharing and particle filtering. Our approach can provide reasonable errors in the estimation, which allow the routing protocol to effectively deliver messages to destination nodes. We evaluate GeoHawk using extensive experimentation in the ONE simulator. We have developed mobility models that approximate the user behaviour in the targeted use ix cases and communication environments. We have experimented with a large variety of configuration parameters that affect the behaviour of the proposed protocol and recorded its performance in terms of message delivery ratio and latency as well as induced network overhead. We show that the GeoHawk’s performance is superior to baseline protocols, namely Epidemic, PRoPHET and WSR

Flexible Application-Layer Multicast in Heterogeneous Networks

This work develops a set of peer-to-peer-based protocols and extensions in order to provide Internet-wide group communication. The focus is put to the question how different access technologies can be integrated in order to face the growing traffic load problem. Thereby, protocols are developed that allow autonomous adaptation to the current network situation on the one hand and the integration of WiFi domains where applicable on the other hand

On-demand content delivery on spontaneous mobile mesh networks

Dissertação de mestrado em Engenharia InformáticaToday there is a vast number of mobile devices. These devices allow people to access services everywhere. Typically a network infrastructure is required to support these services, like a wireless access point or a 3G connection. Sometimes such infrastructure may not exist or may not be available, making services impossible to operate. Ad-hoc networks allow infrastructure-less communication where each device can communicate with other devices from the network without depending on some infrastructure. These networks can be explored in order to provide services. For example, content delivery in case there is no infrastructure available to support the communication. The main objective of this work is to take advantage of the potential of ad-hoc networks to provide some services related with content access. The goal is to achieve a framework that is able to explore ad-hoc networks to successfully deliver content to every interested user. Besides, it should be able to work in different devices and operating systems. In this work, a fully functional framework prototype was implemented, requiring minimal configuration. The result is an off-the-shelf application that needs only a Java Virtual Machine (JVM) to operate. In order to successfully forward content between nodes from the server to the destination, a new routing model was developed that is exclusively based on content IDs instead of addresses. We used HTTP as presentation layer of the framework. This way we enable the customization of the interface by the server. Each user that is already familiarized with HTML pages can easily interact with our system.Hoje em dia existe um grande número de dispositivos móveis que permitem o acesso a serviços em qualquer lado. Para suportar esses serviços é necessária uma infra-estrutura de rede, como por exemplo, um ponto de acesso sem fios ou uma ligação 3G. Quando essa infra-estrutura é inexistente ou não está disponível, os serviços tornam-se inacessíveis. As redes ad-hoc possibilitam a comunicação independente de qualquer infra-estrutura. Estas redes podem ser exploradas por forma a fornecer serviços, tais como o acesso a conteúdo, no caso de não existir uma infra-estrutura de comunicação. O objectivo principal é tirar partido das redes ad-hoc para fornecer serviços de acesso a conteúdo. Queremos obter uma plataforma capaz de fornecer conteúdos aos utilizadores interessados, explorando as redes ad-hoc. Para além disso, deve também ser capaz de operar em diferentes dispositivos e sistemas operativos. Neste trabalho foi implementado um protótipo da plataforma completamente funcional. O resultado final é uma aplicação pronta a ser utilizada, que necessita apenas de uma Java Virtual Machine (JVM). Foi desenhado um novo modelo de encaminhamento baseado, exclusivamente, em IDs de conteúdo, por forma a encaminhar o tráfego entre servidor e cliente. Utilizamos o HTTP como camada de apresentação, dessa forma, o servidor pode ‘desenhar’ o interface. A interacção com o sistema é bastante simples no caso do utilizador estar familiarizado com as páginas HTML

Forming parallel internets and enabling ultra-local economies

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 105-109).Internet-based mobile communications have been increasing rapidly [5], yet there is little or no progress in platforms that enable applications for discovery, context-awareness and sharing of data and services in a peer-wise manner among collections of devices in the same physical area. This is important because proximate devices may need to communicate directly when no infrastructure is available, and because such local access may be an efficient alternative to connecting a large number of sensors, effectors, and people to a readily accessible, universal central system. This thesis presents the design, implementation and evaluation of Cerebro, a system that allows suitably equipped humans and objects in the same physical area to discover each other and share data and services. Cerebro offers two basic services: a presence service that propagates information about local devices through an automatically generated mesh network and an innovative data transport service to transfer data via this network. On top of these services, Cerebro offers an extensible Application Programming Interface (API). In a mobile mesh network with N devices, Cerebro offers an upper bound of O(N) on traffic overhead to maintain presence information at any part of the network and responsiveness to device arrival/departure events that take at most O(N) time to propagate throughout the network. This makes Cerebro a scalable and useful addition to mobile service delivery.by Polychronis Panagiotis Ypodimatopoulos.S.M

Systems for Challenged Network Environments.

Developing regions face significant challenges in network access, making even simple network tasks unpleasant and rich media prohibitively difficult to access. Even as cellular network coverage is approaching a near-universal reach, good network connectivity remains scarce and expensive in many emerging markets. The underlying theme in this dissertation is designing network systems that better accommodate users in emerging markets. To do so, this dissertation begins with a nuanced analysis of content access behavior for web users in developing regions. This analysis finds the personalization of content access---and the fragmentation that results from it---to be significant factors in undermining many existing web acceleration mechanisms. The dissertation explores content access behavior from logs collected at shared internet access sites, as well as user activity information obtained from a commercial social networking service with over a hundred million members worldwide. Based on these observations, the dissertation then discusses two systems designed for improving end-user experience in accessing and using content in constrained networks. First, it deals with the challenge of distributing private content in these networks. By leveraging the wide availability of cellular telephones, the dissertation describes a system for personal content distribution based on user access behavior. The system enables users to request future data accesses, and it schedules content transfers according to current and expected capacity. Second, the dissertation looks at routing bulk data in challenged networks, and describes an experimentation platform for building systems for challenged networks. This platform enables researchers to quickly prototype systems for challenged networks, and iteratively evaluate these systems using mobility and network emulation. The dissertation describes a few data routing systems that were built atop this experimentation platform. Finally, the dissertation discusses the marketplace and service discovery considerations that are important in making these systems viable for developing-region use. In particular, it presents an extensible, auction-based market platform that relies on widely available communication tools for conveniently discovering and trading digital services and goods in developing regions. Collectively, this dissertation brings together several projects that aim to understand and improve end-user experience in challenged networks endemic to developing regions.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91401/1/azarias_1.pd

European Handbook of Crowdsourced Geographic Information

This book focuses on the study of the remarkable new source of geographic information that has become available in the form of user-generated content accessible over the Internet through mobile and Web applications. The exploitation, integration and application of these sources, termed volunteered geographic information (VGI) or crowdsourced geographic information (CGI), offer scientists an unprecedented opportunity to conduct research on a variety of topics at multiple scales and for diversified objectives. The Handbook is organized in five parts, addressing the fundamental questions: What motivates citizens to provide such information in the public domain, and what factors govern/predict its validity?What methods might be used to validate such information? Can VGI be framed within the larger domain of sensor networks, in which inert and static sensors are replaced or combined by intelligent and mobile humans equipped with sensing devices? What limitations are imposed on VGI by differential access to broadband Internet, mobile phones, and other communication technologies, and by concerns over privacy? How do VGI and crowdsourcing enable innovation applications to benefit human society? Chapters examine how crowdsourcing techniques and methods, and the VGI phenomenon, have motivated a multidisciplinary research community to identify both fields of applications and quality criteria depending on the use of VGI. Besides harvesting tools and storage of these data, research has paid remarkable attention to these information resources, in an age when information and participation is one of the most important drivers of development. The collection opens questions and points to new research directions in addition to the findings that each of the authors demonstrates. Despite rapid progress in VGI research, this Handbook also shows that there are technical, social, political and methodological challenges that require further studies and research

Spatial and Temporal Sentiment Analysis of Twitter data

The public have used Twitter world wide for expressing opinions. This study focuses on spatio-temporal variation of georeferenced Tweets’ sentiment polarity, with a view to understanding how opinions evolve on Twitter over space and time and across communities of users. More specifically, the question this study tested is whether sentiment polarity on Twitter exhibits specific time-location patterns. The aim of the study is to investigate the spatial and temporal distribution of georeferenced Twitter sentiment polarity within the area of 1 km buffer around the Curtin Bentley campus boundary in Perth, Western Australia. Tweets posted in campus were assigned into six spatial zones and four time zones. A sentiment analysis was then conducted for each zone using the sentiment analyser tool in the Starlight Visual Information System software. The Feature Manipulation Engine was employed to convert non-spatial files into spatial and temporal feature class. The spatial and temporal distribution of Twitter sentiment polarity patterns over space and time was mapped using Geographic Information Systems (GIS). Some interesting results were identified. For example, the highest percentage of positive Tweets occurred in the social science area, while science and engineering and dormitory areas had the highest percentage of negative postings. The number of negative Tweets increases in the library and science and engineering areas as the end of the semester approaches, reaching a peak around an exam period, while the percentage of negative Tweets drops at the end of the semester in the entertainment and sport and dormitory area. This study will provide some insights into understanding students and staff ’s sentiment variation on Twitter, which could be useful for university teaching and learning management

Recent Trends in Communication Networks

In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges

European Handbook of Crowdsourced Geographic Information

"This book focuses on the study of the remarkable new source of geographic information that has become available in the form of user-generated content accessible over the Internet through mobile and Web applications. The exploitation, integration and application of these sources, termed volunteered geographic information (VGI) or crowdsourced geographic information (CGI), offer scientists an unprecedented opportunity to conduct research on a variety of topics at multiple scales and for diversified objectives. The Handbook is organized in five parts, addressing the fundamental questions: What motivates citizens to provide such information in the public domain, and what factors govern/predict its validity?What methods might be used to validate such information? Can VGI be framed within the larger domain of sensor networks, in which inert and static sensors are replaced or combined by intelligent and mobile humans equipped with sensing devices? What limitations are imposed on VGI by differential access to broadband Internet, mobile phones, and other communication technologies, and by concerns over privacy? How do VGI and crowdsourcing enable innovation applications to benefit human society? Chapters examine how crowdsourcing techniques and methods, and the VGI phenomenon, have motivated a multidisciplinary research community to identify both fields of applications and quality criteria depending on the use of VGI. Besides harvesting tools and storage of these data, research has paid remarkable attention to these information resources, in an age when information and participation is one of the most important drivers of development. The collection opens questions and points to new research directions in addition to the findings that each of the authors demonstrates. Despite rapid progress in VGI research, this Handbook also shows that there are technical, social, political and methodological challenges that require further studies and research.

Performance Analysis and Optimisation of In-network Caching for Information-Centric Future Internet

The rapid development in wireless technologies and multimedia services has radically shifted the major function of the current Internet from host-centric communication to service-oriented content dissemination, resulting a mismatch between the protocol design and the current usage patterns. Motivated by this significant change, Information-Centric Networking (ICN), which has been attracting ever-increasing attention from the communication networks research community, has emerged as a new clean-slate networking paradigm for future Internet. Through identifying and routing data by unified names, ICN aims at providing natural support for efficient information retrieval over the Internet. As a crucial characteristic of ICN, in-network caching enables users to efficiently access popular contents from on-path routers equipped with ubiquitous caches, leading to the enhancement of the service quality and reduction of network loads. Performance analysis and optimisation has been and continues to be key research interests of ICN. This thesis focuses on the development of efficient and accurate analytical models for the performance evaluation of ICN caching and the design of optimal caching management schemes under practical network configurations. This research starts with the proposition of a new analytical model for caching performance under the bursty multimedia traffic. The bursty characteristic is captured and the closed formulas for cache hit ratio are derived. To investigate the impact of topology and heterogeneous caching parameters on the performance, a comprehensive analytical model is developed to gain valuable insight into the caching performance with heterogeneous cache sizes, service intensity and content distribution under arbitrary topology. The accuracy of the proposed models is validated by comparing the analytical results with those obtained from extensive simulation experiments. The analytical models are then used as cost-efficient tools to investigate the key network and content parameters on the performance of caching in ICN. Bursty traffic and heterogeneous caching features have significant influence on the performance of ICN. Therefore, in order to obtain optimal performance results, a caching resource allocation scheme, which leverages the proposed model and targets at minimising the total traffic within the network and improving hit probability at the nodes, is proposed. The performance results reveal that the caching allocation scheme can achieve better caching performance and network resource utilisation than the default homogeneous and random caching allocation strategy. To attain a thorough understanding of the trade-off between the economic aspect and service quality, a cost-aware Quality-of-Service (QoS) optimisation caching mechanism is further designed aiming for cost-efficiency and QoS guarantee in ICN. A cost model is proposed to take into account installation and operation cost of ICN under a realistic ISP network scenario, and a QoS model is presented to formulate the service delay and delay jitter in the presence of heterogeneous service requirements and general probabilistic caching strategy. Numerical results show the effectiveness of the proposed mechanism in achieving better service quality and lower network cost. In this thesis, the proposed analytical models are used to efficiently and accurately evaluate the performance of ICN and investigate the key performance metrics. Leveraging the insights discovered by the analytical models, the proposed caching management schemes are able to optimise and enhance the performance of ICN. To widen the outcomes achieved in the thesis, several interesting yet challenging research directions are pointed out