Encounter gossip: a high coverage broadcast protocol for MANET

PhD ThesisMobile Ad-hoc Networks (MANETs) allow deployment of mobile wireless devices or nodes in a range of environments without any fixed infrastructure and hence at a minimal setup cost. Broadcast support that assures a high coverage (i.e., a large fraction of nodes receiving a broadcast) is essential for hosting user applications, and is also non-trivial to achieve due to the nature of devices and mobility. We propose Encounter Gossip, a novel broadcast protocol, which holds minimal state and is unaware of network topology. Coverage obtained can be made arbitrarily close to 1 at a moderate cost of extra message tra c, even in partition-prone networks. Under certain simplifying assumptions, it is shown that a high coverage is achieved by making a total of O(n ln n) broadcasts, where n is the number of nodes, and the time to propagate a message is O(ln n). The e ect of various network parameters on the protocol performance is examined. We then propose modifications to minimise the number of redundant transmissions without compromising the achieved coverage. Two approaches are pursued: timer based and history based. The e ectiveness of each of these approaches is assessed through an extensive set of simulation experiments in the context of two mobility models. Specifically, we introduce a new heuristic alpha policy which achieves significant reduction in redundancy with negligible reduction in coverage. A generalisation to multiple broadcasts proceeding in parallel is proposed and the protocol is refined to reduce problems that can occur due to the effects of high mobility when transmitting a large number of messages. Finally, we implement and validate Encounter Gossip in the context of a real-life mobile ad-hoc network. All these investigations suggest that the protocol, together with the proposed modifications and re nements, is suited to MANETs of varying degrees of node densities and speeds

Design and performance study of algorithms for consensus in sparse, mobile ad-hoc networks

PhD ThesisMobile Ad-hoc Networks (MANETs) are self-organizing wireless networks that consist of mobile wireless devices (nodes). These networks operate without the aid of any form of supporting infrastructure, and thus need the participating nodes to co-operate by forwarding each other’s messages. MANETs can be deployed when urgent temporary communications are required or when installing network infrastructure is considered too costly or too slow, for example in environments such as battlefields, crisis management or space exploration. Consensus is central to several applications including collaborative ones which a MANET can facilitate for mobile users. This thesis solves the consensus problem in a sparse MANET in which a node can at times have no other node in its wireless range and useful end-to-end connectivity between nodes can just be a temporary feature that emerges at arbitrary intervals of time for any given node pair. Efficient one-to-many dissemination, essential for consensus, now becomes a challenge: enough number of destinations cannot deliver a multicast unless nodes retain the multicast message for exercising opportunistic forwarding. Seeking to keep storage and bandwidth costs low, we propose two protocols. An eventually relinquishing (}RC) protocol that does not store messages for long is used for attempting at consensus, and an eventually quiescent (}QC) one that stops forwarding messages after a while is used for concluding consensus. Use of }RC protocol poses additional challenges for consensus, when the fraction, f n, of nodes that can crash is: 1 4 f n < 1 2 . Consensus latency and packet overhead are measured through simulation indicating that they are not too high to be feasible in MANETs. They both decrease considerably even for a modest increase in network density.Damascus University

Self-Calibration Methods for Uncontrolled Environments in Sensor Networks: A Reference Survey

Growing progress in sensor technology has constantly expanded the number and range of low-cost, small, and portable sensors on the market, increasing the number and type of physical phenomena that can be measured with wirelessly connected sensors. Large-scale deployments of wireless sensor networks (WSN) involving hundreds or thousands of devices and limited budgets often constrain the choice of sensing hardware, which generally has reduced accuracy, precision, and reliability. Therefore, it is challenging to achieve good data quality and maintain error-free measurements during the whole system lifetime. Self-calibration or recalibration in ad hoc sensor networks to preserve data quality is essential, yet challenging, for several reasons, such as the existence of random noise and the absence of suitable general models. Calibration performed in the field, without accurate and controlled instrumentation, is said to be in an uncontrolled environment. This paper provides current and fundamental self-calibration approaches and models for wireless sensor networks in uncontrolled environments

A Secure 3-Way Routing Protocols for Intermittently Connected Mobile Ad Hoc Networks

The mobile ad hoc network may be partially connected or it may be disconnected in nature and these forms of networks are termed intermittently connected mobile ad hoc network (ICMANET). The routing in such disconnected network is commonly an arduous task. Many routing protocols have been proposed for routing in ICMANET since decades. The routing techniques in existence for ICMANET are, namely, flooding, epidemic, probabilistic, copy case, spray and wait, and so forth. These techniques achieve an effective routing with minimum latency, higher delivery ratio, lesser overhead, and so forth. Though these techniques generate effective results, in this paper, we propose novel routing algorithms grounded on agent and cryptographic techniques, namely, location dissemination service (LoDiS) routing with agent AES, A-LoDiS with agent AES routing, and B-LoDiS with agent AES routing, ensuring optimal results with respect to various network routing parameters. The algorithm along with efficient routing ensures higher degree of security. The security level is cited testing with respect to possibility of malicious nodes into the network. This paper also aids, with the comparative results of proposed algorithms, for secure routing in ICMANET

Robotic Wireless Sensor Networks

In this chapter, we present a literature survey of an emerging, cutting-edge, and multi-disciplinary field of research at the intersection of Robotics and Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system that aims to achieve certain sensing goals while meeting and maintaining certain communication performance requirements, through cooperative control, learning and adaptation. While both of the component areas, i.e., Robotics and WSN, are very well-known and well-explored, there exist a whole set of new opportunities and research directions at the intersection of these two fields which are relatively or even completely unexplored. One such example would be the use of a set of robotic routers to set up a temporary communication path between a sender and a receiver that uses the controlled mobility to the advantage of packet routing. We find that there exist only a limited number of articles to be directly categorized as RWSN related works whereas there exist a range of articles in the robotics and the WSN literature that are also relevant to this new field of research. To connect the dots, we first identify the core problems and research trends related to RWSN such as connectivity, localization, routing, and robust flow of information. Next, we classify the existing research on RWSN as well as the relevant state-of-the-arts from robotics and WSN community according to the problems and trends identified in the first step. Lastly, we analyze what is missing in the existing literature, and identify topics that require more research attention in the future

Time-Varying Graphs and Dynamic Networks

The past few years have seen intensive research efforts carried out in some apparently unrelated areas of dynamic systems -- delay-tolerant networks, opportunistic-mobility networks, social networks -- obtaining closely related insights. Indeed, the concepts discovered in these investigations can be viewed as parts of the same conceptual universe; and the formal models proposed so far to express some specific concepts are components of a larger formal description of this universe. The main contribution of this paper is to integrate the vast collection of concepts, formalisms, and results found in the literature into a unified framework, which we call TVG (for time-varying graphs). Using this framework, it is possible to express directly in the same formalism not only the concepts common to all those different areas, but also those specific to each. Based on this definitional work, employing both existing results and original observations, we present a hierarchical classification of TVGs; each class corresponds to a significant property examined in the distributed computing literature. We then examine how TVGs can be used to study the evolution of network properties, and propose different techniques, depending on whether the indicators for these properties are a-temporal (as in the majority of existing studies) or temporal. Finally, we briefly discuss the introduction of randomness in TVGs.Comment: A short version appeared in ADHOC-NOW'11. This version is to be published in Internation Journal of Parallel, Emergent and Distributed System

Probabilistic Path Discovery with Snakes in Ad Hoc Networks

Many routing protocols for wireless ad hoc networks proposed in the literature use flooding to discover paths between the source and the destination node. Despite various broadcast optimization techniques, flooding remains expensive in terms of bandwidth and energy consumption. In general, O(N) nodes are involved to discover a path. In this thesis, we prove through a theoretical model that probabilistic path discovery is possible by involving O(sqrt(N)) nodes only. The constant factor depends on the desired path discovery probability. Using a novel network primitive that we call snakes, we introduce practical and cheap probabilistic path discovery algorithms. These algorithms rely on the same network model and assumptions as its flooding counterparts, i. e., that the network is unstructured and that nodes only know their immediate (one-hop) neighbors. Numerical simulations in a static network show that these algorithms achieve path discovery probabilities close to the theoretical optimum. We further present a snake-based algorithm for mobile ad hoc networks and several techniques to enhance the performance in some specific networks

SOCIAL AND LOCATION BASED ROUTING IN DELAY TOLERANT NETWORKS

Delay tolerant networks (DTNs) are a special type of wireless mobile networks which may lack continuous network connectivity. Routing in DTNs is very challenging as it must handle network partitions, long delays, and dynamic topology in such networks. Recently, the consideration of social characteristics of mobile nodes provides a new angle of view in the design of DTNs routing protocols. In many DTNs, a multitude of mobile devices are used and carried by people (e.g. pocket switched networks and vehicular networks), whose behaviors are better described by social models. This opens the new possibilities of social-based routing, in which the knowledge of social characteristics is used for making better forwarding decision. However, the social relations do not necessarily reflect the true device communication opportunities in a dynamic DTN. On the other hand, the increasing availability of location technologies (GPS, GSM networks, etc.) enables mobile devices to obtain their locations easily. Consider that an individual’s location history in the real world implies his/her social interests and behaviors to some extent, in this dissertation, we study new social based DTN routing protocols, which utilize location and/or social features to achieve efficient and stable routing for delay tolerant networks. We first incorporate the location features into the social-based DTN routing methods to improve their performance by treating location similarity among nodes as possible social relationship. Then, we dis- cuss the possibility and methods to further improve routing performance by adding limited amount of throw-boxes into the networks to aid the DTN relay. Several throw-boxes based routing protocols and location selection methods for throw-boxes are proposed. All pro- posed routing methods are evaluated via extensive simulations with real life trace data (such as MIT reality, Nokia MDC, and Orange D4D)

Resource savings in delay tolerant networks

Tese de mestrado, Engenharia Informática (Engenharia de Software) Universidade de Lisboa, Faculdade de Ciências, 2018Este documento foca-se no trabalho que foi feito na dissertação de mestrado no Departamento de Informática da Faculdade de Ciências da Universidade de Lisboa ao longo de um ano. O objectivo inicial foi criar um protótipo de middleware em ambiente de simulador que servisse o propósito de facilitar disseminação de dados num ambiente urbano de cidade inteligente. Apesar de apontámos para uma solução mais genérica possível, por de trás deste objectivo e servindo de motivação existe um cenário de caso de uso no qual nos focámos. Este cenário descreve uma cidade na qual a recolha do lixo tem que ser otimizada e em cada caixote existe um sensor que produz leituras do nível atual de enchimento. O desafio coloca-se em disseminar a informação produzida por estes sensores de uma forma eficaz e sem grandes gastos de recursos. Como tal, recorremos ao facto de já existir uma infraestrutura subjacente para resolver o problema. Através da utilização de carros de polícia, bombeiros, táxis ou por exemplo camiões do lixo, fazemos com que estes ajudem na recolha das leituras feitas pelos sensores. O facto de esta recolha de leituras ser feita localmente por veículos que circulam na cidade, permite que as baterias dos sensors sofram uma descarga menor do que se tivessem que enviar diretamente a informação para o destino final mas utilizando recursos mais dispendiosos. Para melhorar esta ideia e de forma a que o resultado final fosse o mais completo possível, começámos então por fazer um estudo do estado da arte. Ao ler e considerar trabalho feito nas áreas de espaços de tuplos, redes tolerantes a atraso, cidades inteligentes, simuladores de redes, redes de sensores e difusão epidémica foi possível melhorar consideravelmente o produto final desta dissertação. Este estudo de outros trabalhos é sem dúvida um passo muito importante no decorrer desta dissertação, pois através de observação, quer de lacunas, quer de pontos fortes existentes noutras soluções, permitiu considerar e pensar de forma competente a solução a desenvolver. Partindo então deste estudo foi definido um modelo de sistema que permitiu perceber de forma eficaz alguns requisitos e condições que tinham de ser cumpridos. Dado este trabalho inicial foi então definido a especificação para o middleware. Foi determinada uma semântica para o espaço de tuplos que suporta a persistência de dados para cada um dos nós da rede. Após isto, foi implementado uma versão de espaços de tuplos em C/C++ que cumprisse esta mesma semântica. Em comunhão foi elaborado um protocolo que permitisse que estes espaços de tuplos fossem sincronizados entre os vários nós existentes na rede. Este protocolo foi concebido utilizando conceitos de flooding e difusão epidémica. Para além disso foi criado um canal prioritário para que se podesse proceder ao envio de leituras cujo o cariz fosse mais importante. De forma a manter um certo nível de eficiência no middleware, foi também criado um mecanismo de remoção de tuplos duplicados na rede. Este mecanismo recorreu ao uso de épocas definidas em tempo de configuração. Foi também delineado uma forma parcimoniosa de serialização dos tuplos trocados na rede com o objetivo de melhorar a eficiência deste middleware. Por fim, criámos uma forma de atualização de código para os sensores que também utiliza a infraestrutura de cidade para se disseminar para cada sensor. Toda esta implementação foi feita especificamente para o Network Simulator 3, sendo desenvolvida em C/C++. O simulador de redes em questão tornou-se extremamente útil pois permitiu testar numa fase embrionária um cenário que dado a escala seria difícil de avaliar numa situção real. Pelos inúmeros módulos já existentes de raiz, foi possível implementar características como comunicação 3G/4G ou simulação de bateria em cada sensor. De forma a oferecer uma grande flexibilidade para que este middleware possa ser aplicado em diferentes cenários com diferentes características, criámos uma configuração parametrizável de valores que fazem com que o middleware se adapte. Esta flexibilidade é muito importante para o seu funcionamento dado que, muitos ambientes urbanos têm características diferentes, como por exemplo densidade populacional, o que por sua vez, afeta o número de veículos presentes na infraestrutura. Após a implementação do protótipo de middleware passámos então à fase de avaliação. Para esta fase de avaliação começámos em primeiro lugar, por procurar dois padrões de mobilidade de veículos em ambientes urbanos. Estes padrões servem para ser aplicados no simulador de rede de forma a criar um movimento realista e relevante para as nossas simulações. Os cenários escolhidos foram: um conjunto de posições de GPS de múltiplos táxis na cidade de Roma e também o registo de posições de GPS para uma rede de transportes de autocarro na zona urbana de Seattle. Apesar de haver algumas diferenças relevantes entre estes dois padrões, como por exemplo a dimensão total do cenário, esta mesma discrepância entre eles serve para avaliar o middleware em diferentes ambientes. Escolhidos então estes padrões foi desenhado um plano para os testes. De forma a criar alguma relevância estatística foi feita uma bateria de simulações sobre o middleware, sendo no total efectuadas 480 simulações. Com os resultados destas simulações, dos quais foram extraídos valores como taxa de entrega e latência de entrega, foram utilizadas algumas métricas relevantes para fazer uma avaliação. Usando gráficos gerados, foi possível efetuar uma discussão da eficiência do middleware podendo avaliar certas situações nas quais determinadas características se sobressaíram. No entanto ficou claro que é ainda necessário fazer uma avaliação muito mais extensa de todo o trabalho dado a complexidade inerente aos múltiplos parâmetros que existem no middleware, que sendo dispostos em diferentes configurações podem apresentar resultados muito díspares. Por fim, foram tiradas algumas conclusões do que foi feito e das limitações que atualmente apresenta. Nesta conclusão foi revisto se os objectivos que inicialmente se propôs foram de alguma forma cumpridos. Foi também discutido algum trabalho que pode vir a ser feito no futuro. Este trabalho futuro apresenta algumas funcionalidades que melhoram a eficiência e usabilidade do middleware. Um exemplo é o enriquecimento da semântico do espaço de tuplos utilizado que permitirá ao utilizador efectuar mais facilmente pesquisas de tuplos com um esforço mais reduzido.This document focuses on the work done on the master thesis at the Informatics Department in the Faculdade de Ciências da Universidade de Lisboa. With this work we aim at offering a reliable middleware that is capable of supporting data dissemination in a network composed of different types of hardware. Mainly these different components are sensors and mobile devices. We hope to offer a solution that is deployable in scenarios that have an high degree of heterogeneity without compromising the quality of service and functionalities of the applications used with the middleware. With these type of proposal we expect to cover many cases of ubiquitous computing such as the ones we find in smart cities scenarios. Although our solution is aiming to be as generic as possible we take a practical case into account in order to provide a working example of our work. We take advantage of the infrastructure now available in some cities such as a mobile ad hoc network composed of public service vehicles. Doing so we will use our work in a garbage collection project where sensors read data from garbage cans in order to inform a set of base stations of their garbage levels. With this we allow the optimization of garbage collection in the future. Also by testing our middleware in this scenario we intend to gather more information that may allow for future improvements in the middleware. So far we were able to implement a working prototype simulation designed for the Network Simulator 3. In this simulation we used some mobility patterns and tested the middleware in order to achieve results on its delivery rate and other metrics. By perusing previous work done in studied areas of research such as tuple spaces and wireless sensor networks, we were able improve our concept. As a goal we look forward to create a piece of software that contributes to the community, making ease the process of going about our routines, work and the way we live in a more automated and pleasant smart city