Wireless and Mobile (WAM) networks have been evolving and extending their reach to more aspects of human activity for years. As such, networks have been deployed in wider and broader physical range and circumstances, so that end-to-end contemporaneous connectivity is no longer guaranteed. To address this connectivity challenge, recent research work on Disruption Tolerant Network (DTN) paradigm uses intermediate nodes to store data while waiting for transfer opportunities towards the destination. However, this work differs from conventional research work in WAM, e.g., Mobile Ad hoc Network (MANET) routing, since the connectivity assumptions are so different. In this thesis, we present the WAM Continuum framework which aims to provide a unified treatment of wireless and mobile networks. The framework is based on the construction of a WAM continuum that defines the space of networks and a corresponding formalism by which one can group related WAMs into classes that map into design and operational regimes. We show a specific instantiation of this framework that classifies networks according to their path properties and apply it to networks described by traces from both real platforms and synthesized mobility models. Effect of introducing controllable node mobility, e.g., message ferrying, is quantitatively evaluated in our study. We extend this framework in a manner that enables the classification of a WAM's energy "sufficiency" depending on a combination of the network connectivity properties, available energy, and power management scheme. As another extension under the same WAM continuum framework, this thesis studies the interaction of mobile computation collaboration and underlying network connectivity characteristics. Classification results from our framework indicate that heterogeneous connectivity may exist in WAM networks. In such cases, protocols from different routing paradigms need to work together to provide effective data communication. We focus on integration of MANET routing and message ferrying in clustered DTNs. A hybrid routing approach is developed in which both MANET routing and message ferrying are used to explore available connectivity in clusters via gateway nodes. Different data aggregation as well as transmission scheduling algorithms are proposed. To achieve better performance, we also study the ferry route design problem in the clustered DTNs and develop three route design algorithms. This thesis work also includes our experience to address challenges associated with new data communication requirements in oil field operations at remote areas. Backed up by a comprehensive measurement study of long range data links provided by satellite and cellular services, we develop a WAM network where multiple data links are jointly used to achieve an effective data communication solution in the challenged environment.

Currently there is ongoing research in the field of Mobile Ad-hoc Networks (MANET) for several different scenarios. Research has focused on topology related challenges such as routing mechanisms or addressing systems, as well as security issues like traceability of radio communication or encryption. In addition, there are very specific research interests such as the effects of directional antennas for MANETs or optimized transmission techniques for minimal power consumption or range optimization. Unmanned aerial vehicles (UAVs), and unmanned aerial systems (UAS) in general, need wireless systems in order to communicate. Current UAS are very flexible and allow for a wide spectrum of mission profiles by means of utilizing different UAVs, according to the requirements at hand. Each mission poses special needs and requirements on the internal and external UAS communication and special mission scenarios calling for UAV swarms increase the complexity and require specialized communication solutions. UAS have specific needs not provided by the general research, but are, on the other hand, to diversified to make much use of narrowly focused developments; UAS form a sufficiently large research area for application of MANETs to be considered as an independent group with specialized needs worthy of tailored implementations of MANET principles. MANET research has not tackled a general approach to UAS although some sources show specific applications involving UAVS. This work presents some new aspects for the development of of ad-hoc wireless networks for UAVs and UAS and focuses on their specialties and needs. A general framework for MANET development is proposed. Furthermore, the proposed specific evaluation scenarios provide for a UAS focused comparison of MANET performance.

Several emerging wireless applications require direct transmission between mobile terminals. Examples of these applications are mobile ad-hoc wireless networks, intelligent transportation systems, relay-based cellular networks, and future combat systems. Development of these mobile-to-mobile (M-to-M) systems depends on a good characterization of channel propagation. Another important consideration in modern communication systems is the use of multipath propagation to improve reliability and capacity of wireless systems. This is achieved by employing multiple antennas in multiple-input multiple-output (MIMO) systems and using techniques such as transmit and receive diversity. Considering the demand for high-speed wireless services, MIMO M-to-M systems are the leading candidates for future communication systems. To enable the successful design of MIMO M-to-M systems, our research focuses on modeling of MIMO M-to-M multipath fading channels and on diversity techniques for MIMO systems. Specifically, we propose two-dimensional (2-D) and three-dimensional (3-D) MIMO M-to-M statistical channel models that encompass narrowband and wideband MIMO channel scenarios for macro- and micro-cell environments. Furthermore, we validate the new models against measured data and find very close agreement between them. Using our 3-D models, we also investigate different antenna array configurations and their effect on the capacity of MIMO M-to-M systems. Contrary to common assumptions, we have found that there is no significant loss of capacity if the antenna array is tilted from the horizontal plane. Finally, we propose the design criteria for space-time coded continuous phase modulated systems. Our work would provide other researchers the tools needed to design and test future MIMO M-to-M communication systems.

This research is motivated by the recent developments in the Internet Engineering Task Force (IETF) to support seamless integration of moving networks deployed in vehicles to the global Internet. The effort, known as Network Mobility (NEMO), paves the way to support high-speed Internet access in mass transit systems, e.g. trains; buses; ferries; and planes; through the use of on-board mobile routers embedded in the vehicle. One of the critical research challenges of this vision is to achieve high-speed and reliable back-haul connectivity between the mobile router and the rest of the Internet. The problem is particularly challenging due to the fact that a mobile router must rely on wireless links with limited bandwidth and unpredictable quality variations as the vehicle moves around. In this thesis, the multi-homing concept is applied to approach the problem. With multi-homing, mobile router has more than one connection to the Internet. This is achieved by connecting the mobile router to a diverse array of wireless access technologies (e.g., GPRS, CDMA, 802.11, and 802.16) and/or a multiplicity of wireless service providers. While the aggregation helps addressing the bandwidth problem, quality variation problem can be mitigated by employing advanced traffic engineering techniques that dynamically control inbound and outbound traffic over multiple connections. More specifically, the thesis investigates traffic engineering solutions for mobile networks that can effectively address the performance objectives, e.g. maximizing profit for mobile network operator; guaranteeing quality of service for the users; and maintaining fair access to the back-haul bandwidth. Traffic engineering solutions with three different levels of control have been investigated. First, it is shown, using detailed computer simulation of popular applications and networking protocols(e.g., File Transfer Protocol and Transmission Control Protocol), that packet-level traffic engineering which makes decisions of which Internet connection to use for each and every packet, leads to poor system throughput. The main problem with packet-based traffic engineering stems from the fact that in mobile environment where link bandwidths and delay can vary significantly, packets using different connections may experience different delays causing unexpected arrivals at destinations. Second, a maximum utility flow-level traffic engineering has been proposed that aims to maximize a utility function that accounts for bandwidth utilization on the one hand, and fairness on the other. The proposed solution is compared against previously proposed flow-level traffic engineering schemes and shown to have better performance in terms of throughput and fairness. The third traffic engineering proposal addresses the issue of maximizing operator?s profit when different Internet connections have different charging rates, and guaranteeing per user bandwidth through admission control. Finally, a new signaling protocol is designed to allow the mobile router to control its inbound traffic.

The future Internet will need to cater for an increasing number of powerful devices and entire groups of networks to roam in heterogeneous access networks. The current approach towards meeting such requirements, which is to retrofit mobility solutions to different layers of the protocol stack, has given rise to an increasingly fragmented network control layer. Furthermore, retrofitting solutions in an ad-hoc manner to the protocol stack does not provide consistent support from the network to different applications. This lack of a common control layer for facilitating roaming in heterogeneous networking environments represents a crucial challenge both technically and from a user perspective. To this end, a novel mobility architecture forms the basis and the first part of this dissertation. The work on investigating current network mobility solutions and improving these solutions if deemed necessary, in order to reuse within the novel mobility architecture constitutes the second part of this dissertation. The IETF standard protocol for network mobility was implemented and its performance was analysed on a real networking environment. This enabled to identify problems in the standard which affect the handover and routing performance. To address the identified routing and protocol header overheads of the standard network mobility protocol a novel optimal routing framework, OptiNets was proposed. To address the handover latency issues, optimizations to IPv6 network attachment were incorporated and also an access technology independent multiple interface Make-Before-Break handover mechanism was proposed. The viability of the OptiNets framework and the handover optimizations were demonstrated by analysis and by implementation. A more general external factor that affects the performance of mobile networks which is bandwidth scarcity of Wireless Wide Area Networks was addressed, by proposing a bandwidth fuelling architecture for on-board mobile networks. The feasibility of the bandwidth fuelling architecture was analysed by implementing a prototype and evaluating its performance.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Kartik Gopalan, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains ix, 46 pages. Includes bibliographical references.

Made available in DSpace on 2015-03-26T13:28:35Z (GMT). No. of bitstreams: 1 texto completo.pdf: 8031518 bytes, checksum: 187f1c8078747afc55195475e89c6e44 (MD5) Previous issue date: 2014-07-22 / Over time has increased the need for low cost positioning of the populatio, and for this reason the demand for navigation devices has grown considerably in all levels of users of these devices, the population in general has greater access to smartphones because of its many features. Smartphones using micro GNSS receiver has a main component of positioning, where the pseudorange is its basic observable. The data sources for GPS corrections are increasingly available to the community through institutions as the IBGE with the Brazilian Network for Continuous Monitoring (RBMC). Thus, there is a greater possibility of improvement in accuracy of positioning these devices with the post- processed relative positioning and even in real time. With these possibilities and needs, this study aims the establishment of methodology that improves the accuracy in the positioning devices using micro GNSS receiver with a recursive least squares estimation with the Kalman gain matrix applied in relative positioning static by double difference of pseudorange in short baselines. To verify the effectiveness of this methodology is used SiRFstar IV micro receiver data which receives data only in L1 frequency GPS constellation. Was used reference RBMC stations to process these data. With tracking 15 minutes in known points had a mean deviation in the horizontal component of the plane coordinates 29 cm for post-processing and 98 cm for the real time processing, and, for the single point positioning average deviation was 6 meters. With this, it was concluded that the use of static methods for processing on recursive least squares estimation improves the accuracy of positioning significantly, where mobile devices that were previously given only to navigation may also be used for mapping. / Com o passar do tempo aumentou a necessidade da população em posicionamento a baixo custo, e por este motivo a procura por aparelhos de navegação tem crescido consideravelmente em todos os níveis de usuários. Destes dispositivos, a população no geral tem maior acesso aos smartphones devido a suas diversas funcionalidades. Os smartphones utilizam de microrreceptor GNSS como principal componente de posicionamento, sendo que sua observável básica é a pseudodistância derivada do código C/A. As fontes de dados para correções GPS estão cada vez mais disponíveis para a comunidade por meio de instituições como o IBGE com a Rede Brasileira de Monitoramento Continuo dos Sistemas GNSS (RBMC). Com isso, tem-se uma maior possibilidade de melhorias na acurácia do posicionamento destes dispositivos com o posicionamento relativo pós-processado e até mesmo em tempo real. Com estas possibilidades e necessidades, este trabalho tem como objetivo o estabelecimento de metodologia que melhore a acurácia no posicionamento de dispositivos móveis que utilizam microrreceptor GNSS, utilizando a estimativa de mínimos quadrados recursiva com a matriz de ganho de Kalman aplicada no posicionamento relativo estático por dupla diferença da pseudodistância em linhas de base curtas. Para verificar a eficácia desta metodologia utilizou-se dados do microrreceptor SiRFstar IV que recebe dados na frequência L1 da constelação GPS. Foram utilizadas as estações de referência da RBMC para o processamento destes dados. Com rastreios de 15 minutos em pontos de coordenadas conhecidas teve-se um desvio médio na componente horizontal das coordenadas planas de 29 centímetros para o pós- processamento e 98 centímetros para o processamento em tempo real, sendo que, para o posicionamento por ponto simples o desvio médio foi de 6 metros. Com isso, concluiu-se que a utilização da metodologia de processamento relativo estático por estimativa dos mínimos quadrados recursiva melhorou a acurácia do posicionamento de forma significativa, onde dispositivos móveis 14que até então eram indicados somente para navegação podem ser utilizados também para mapeamento.

In developing countries, the mobile phone market has matured in terms of subscription, penetration and mobile centric1 services. In turn, people have integrated mobile phones into their daily lives. The interaction opportunities that have evolved in business and social life have given students at Higher Educational Institutions (HEIs) grounds to anticipate similar opportunities within their learning environments. In the context of developing countries, students primarily access information through mobile phones and there seems to be a disconnection between how HEI provide informational services and how students want to access the services. Therefore, HEIs are challenged with shifting from their traditional information distribution practices into integrating mobile centric services. Literature describes several models of providing mobile centric services in learning settings but there is a paucity of research that address the disconnection between students’ mobile centric needs and expectations against the HEIs’ provision of such services. Therefore, this study proposes a Framework for providing mobile centric services to students at HEIs in Open Distance e-Learning (ODeL) context in South Africa. The potential contribution of the framework is that it can facilitate strategic planning and implementation of mobile centric services whilst ensuring the needed synergies with students and academics. The research is grounded in interpretive philosophy and was undertaken as a single case study. The case study employed mixed method design for data collection. The advantage of mixed method design is that it enables both qualitative and quantitative data to be collected from a variety of sources and triangulation of results to get a complete picture of the phenomenon under study. The research was undertaken in four phases. Phase 1 of the study was a literature analysis carried out to identify the components for providing mobile centric services that facilitate students with information access and interaction. The objective was to provide a conceptual framework that would direct the search for evidence and organise the results. Phase 2 of the study employed the conceptual framework developed in Phase 1 to identify the units of analysis and to design the data collection instruments. Phase 3 of the study focused on collecting data within a single case study with embedded units of analysis. Data collection included Policy document analysis, Tool observation analysis, Student surveys and Lecturer interviews. The data collected from the case study was analysed with the view of enhancing the components of the conceptual framework developed in Phase 1. The enhancement of the components of the conceptual framework carried out in Phase 3 directed the development of the Framework for providing mobile centric services to students at HEIs in ODeL context in South Africa as presented in Phase 4. This adds new knowledge in addressing the literature gap between the mobile centric needs and expectations of students and the provision of mobile centric services at HEIs. The framework has practical value in that its components can guide HEIs in determining the mobile centric readiness of their institutions, the needs of the stakeholders, the context of use, the identification of mobile centric resources and the managing of constraints. Mobile centric refers to the preference of accessing and interacting with information services through a mobile device such as a mobile phone. / Computing / Ph. D. (Information Systems)

Data-centric security is significant in understanding, assessing and mitigating the various risks and impacts of sharing information outside corporate boundaries. Information generally leaves corporate boundaries through mobile devices. Mobile devices continue to evolve as multi-functional tools for everyday life, surpassing their initial intended use. This added capability and increasingly extensive use of mobile devices does not come without a degree of risk - hence the need to guard and protect information as it exists beyond the corporate boundaries and throughout its lifecycle. Literature on existing models crafted to protect data, rather than infrastructure in which the data resides, is reviewed. Technologies that organisations have implemented to adopt the data-centric model are studied. A utopian model that takes into account the shortcomings of existing technologies and deficiencies of common theories is proposed. Two sets of qualitative studies are reported; the first is a preliminary online survey to assess the ubiquity of mobile devices and extent of technology adoption towards implementation of data-centric model; and the second comprises of a focus survey and expert interviews pertaining on technologies that organisations have implemented to adopt the data-centric model. The latter study revealed insufficient data at the time of writing for the results to be statistically significant; however; indicative trends supported the assertions documented in the literature review. The question that this research answers is whether or not current technology implementations designed to mitigate risks from mobile devices, actually address business requirements. This research question, answered through these two sets qualitative studies, discovered inconsistencies between the technology implementations and business requirements. The thesis concludes by proposing a realistic model, based on the outcome of the qualitative study, which bridges the gap between the technology implementations and business requirements. Future work which could perhaps be conducted in light of the findings and the comments from this research is also considered.

[pt] Ao mesmo tempo em que sistemas de processamento de fluxo de dados devem prover serviços de análise e manipulação de dados ininterruptamente (disponibilidade 24x7), eles comumente também precisam lidar com mudanças em seus ambientes de execução (e.g., alterar a topologia da rede) e nos requisitos que eles devem cumprir (e.g., adição de novas funções de processamento dos fluxos de dados). Por um lado, reconfiguração dinâmica de software (i.e., a capacidade de substituir parte do software em tempo de execução) é uma característica desejável. Por outro lado, sistemas de fluxo de dados podem sofrer com a interrupção e sobrecarga causada pela reconfiguração. Por conta da necessidade de reconfigurar (i.e., evoluir) o sistema ao mesmo tempo em que o sistema não pode ser interrompido (i.e., bloqueado), reconfiguração consistente e não bloqueante é ainda considerada um problema em aberto na literatura. Esta tese apresenta e valida uma abordagem não quiescente para reconfiguração dinâmica de software que preserva a consistência de sistemas de fluxo de dados distribuídos. A abordagem proposta permite que o sistema seja reconfigurado gradual e suavemente, sem precisar interromper o processamento do fluxo de dados ou atingir a quiescência. A avaliação indica que a abordagem proposta realiza reconfiguração distribuída consistentemente e tem um impacto desprezível sobre a diminuição na disponibilidade e no desempenho do sistema. Além disto, a implementação da abordagem proposta teve um desempenho melhor em todos os testes comparativos. / [en] While many data stream systems have to provide continuous (24x7) services with no acceptable downtime, they also have to cope with changes in their execution environments and in the requirements that they must comply (e.g., moving from on-premises architecture to a cloud system, changing the network technology, adding new functionality or modifying existing parts). On one hand, dynamic software reconfiguration (i.e., the capability of evolving on the fly) is a desirable feature. On the other hand, stream systems may suffer from the disruption and overhead caused by the reconfiguration. Due to the necessity of reconfiguring (i.e., evolving) the system whilst the system must not be disrupted (i.e., blocked), consistent and non-disruptive reconfiguration is still considered an open problem. This thesis presents and validates a non-quiescent approach for dynamic software reconfiguration that preserves the consistency of distributed data stream processing systems. Unlike many works that require the system to reach a safe state (e.g., quiescence) before performing a reconfiguration, the proposed approach enables the system to smoothly evolve (i.e., be reconfigured) in a non-disruptive way without reaching quiescence. The evaluation indicates that the proposed approach supports consistent distributed reconfiguration and has negligible impact on availability and performance. Furthermore, the implementation of the proposed approach showed better performance results in all experiments than the quiescent approach and Upstart.