An important aspect of wireless networks is their dynamic behavior. The conventional protocol stack is inflexible as various protocol layers communicate in a strict manner. In such a case the layers are designed to operate under the worst conditions as opposed to adapting to changing conditions. This leads to inefficient use of spectrum and energy. Adaptation represents the ability of network protocols and applications to observe and respond to channel conditions. Traditional simulation methodologies independently model the physical and higher layers. When multiple layer simulations are required, an abstraction of one layer is inserted into the other to provide the multiple layer simulation. However, recent advances in wireless communication technologies, such as adaptive modulation and adaptive antenna algorithms, demand a cross layer perspective to this problem in order to provide a sufficient level of fidelity. However, a full simulation of both layers often results in excessively burdensome simulation run-times. The benefits and possible parametric characterization issues arising due to the cross-layer integration of lower physical and higher network layers are investigated in this thesis. The primary objective of investigating cross-layer simulation techniques is to increase the fidelity of cross-layer network simulations while minimizing the simulation runtime penalties. As a study of cross-layer system design a medium access control (MAC) scheme is studied for a MANET wherein the nodes are equipped with smart antennas. Traditional MAC protocols assume the use of omnidirectional antennas. Nodes with directional antennas are capable of transmitting in certain directions only and significantly reduce the chances of collision and increase the effective network capacity. MANETs using omni-directional antennas severely limit system performance as the entire space around a node up to its radio range is seen as a single logical channel. In this research a MAC protocol is studied that exploits space division multiple access at the physical layer. This is a strong example where physical and MAC design must be carried out simultaneously for adequate system performance. Power control is a very important in the design of cellular CDMA systems which suffer from the near-far problem. Finally, the interaction between successive interference cancellation (SIC) receivers at the physical layer and power control, which is a layer 2 radio resource management issue, is studied. Traffic for future wireless networks is expected to be a mix of real-time traffic such as voice, multimedia teleconferencing, and games and data traffic such as web browsing, messaging, etc. All these applications will require very diverse quality of service guarantees. A power control algorithm is studied, which drives the average received powers to those required, based on the QoS requirements of the individual users for a cellular CDMA system using SIC receivers. / Master of Science

Les réseaux ad hoc dynamiques qui évoluent de manière non planifiée et imprévisible sont souvent étudiés en faisant l’hypothèse d’une composition et d’une topologie qui évoluent peu et relativement lentement. Il est alors possible de proposer dans ce contexte faiblement mobile des mécanismes (comme par exemple du routage, des infrastructures PKI, etc.) qui permettent aux applications conçues pour les réseaux statiques de continuer à fonctionner. Les travaux présentés dans cette thèse sont au contraire centrés sur lesréseaux ad hoc fortement dynamiques (iMANets). Les nœuds qui les constituent sont extrêmement mobiles et volatils, ce qui engendre des modifications incessantes et rapides de topologie. Les contributions principales de cette thèse sont (i) la définition d’une algèbre nommée CiMAN (Calculus for highly Mobile Ad hoc Networks) qui permet de modéliser les processus communicants dans ces réseaux ad hoc fortement mobiles, (ii) l’utilisation de cette algèbre pour prouver la correction d’algorithmes dédiés à ces réseaux, et (iii) unmiddleware et des applications de référence adaptés à ce contexte. / Mobile ad hoc networks that evolve in an unplanned and unpredictable mannerare often studied assuming that their composition and their topology evolve relatively slowly. In this context of weak mobility, it is then possible to propose mechanisms (such asrouting, Public Key Infrastructure, etc.) which make the application designed for a static context still operational. At the opposite, the work presented in this thesis focuses on highlymobile ad hoc networks (iMANets). The nodes of these networks are extremely mobile,bringing ceaseless and fast changes in the network topology. The main contributions of this thesis are (i) the definition of an algebra called CiMAN (Calculus for highly Mobile Adhoc Networks) which makes it possible to model communicating processes in these highly mobile ad hoc networks, (ii) the use of this algebra to prove the correctness of algorithms dedicated to these networks, and (iii) a middleware and reference applications specifically designed for this context.

La croissance explosive des réseaux sans fil et l’augmentation du nombre de dispositifs sans fil ont soulevé de nombreuses difficultés techniques dans la planification et l’analyse de ces réseaux. Nous utilisons la modélisation continue, utile pour la phase initiale de déploiement et l’analyse à grande échelle des études régionales du réseau. Nous étudions le problème de routage dans les réseaux ad hoc, nous définissons deux principes d’optimisation du réseau: le problème de l’utilisateur et du système. Nous montrons que les conditions d’optimalité d’un problème d’optimisation construit d’une manière appropriée coïncide avec le principe de l’optimisation de l’utilisateur. Pour fonctions de coût différentes, nous résolvons le problème de routage pour les antennes directionnelles et omnidirectionnelles. Nous trouvons également une caractérisation des voies du coût minimum par l’utilisation extensive du Théorème de Green dans le cas d’antennes directionnelles. Dans de nombreux cas, la solution se caractérise par une équation aux dérivés partielles. Nous proposons l’analyse numérique par éléments finis qui donne les limites de la variation de la solution par rapport aux données. Lorsque nous permettons la mobilité des origines et destinations, on trouve la quantité optimale de relais actif. Dans les réseaux MIMO, nous montrons que, même lorsque la chaîne offre un nombre infini de degrés de liberté, la capacité est limitée par le rapport entre la taille du réseau d’antennes, la station de base, la position des mobiles et la longueur d’onde du signal. Nous constatons également l’association optimale mobile pour différentes politiques et distributions des utilisateurs. / The growing number of wireless devices and wireless systems present many challenges on the design and operation of these networks. We focus on massively dense ad hoc networks and cellular systems. We use the continuum modeling approach, useful for the initial phase of deployment and to analyze broad-scale regional studies of the network. We study the routing problem in massively dense ad hoc networks, and similar to the work of Nash, and Wardrop, we define two principles of network optimization: user- and system-optimization. We show that the optimality conditions of an appropriately constructed optimization problem coincides with the user-optimization principle. For different cost functions, we solve the routing problem for directional and omnidirectional antennas. We also find a characterization of the minimum cost paths by extensive use of Green’s theorem in directional antennas. In many cases, the solution is characterized by a partial differential equation. We propose its numerical analysis by finite elements method which gives bounds in the variation of the solution with respect to the data. When we allow mobility of the origin and destination nodes, we find the optimal quantity of active relay nodes. In Network MIMO systems and MIMO broadcast channels, we show that, even when the channel offers an infinite number of degrees of freedom, the capacity is limited by the ratio between the size of the antenna array at the base station and the mobile terminals position and the wavelength of the signal. We also find the optimal mobile association for the user- and system-optimization problem under different policies and distributions of the users.

La mobilité est une composante importante de la liberté des personnes. L’évolution des moyens technologiques y contribue au premier chef. Outre la question du transport, celle du maintien du lien entre les individus est en ce sens particulièrement prégnante. Elle a mis à rude épreuve la notion de réseaux de télécommunications puisqu’il s’agit de répondre, pour des individus éparpillés ou concentrés, mais mobiles, au besoin de rester reliés. De l’ère des réseaux analogiques à celle des réseaux numériques, de l’ère des réseaux filaires à celle des réseaux sans fil et mobiles, la technologie n’a cessé d’évoluer. Ces dernières décennies ont vu apparaître des réseaux numériques sans fil, où non seulement il y a mobilité des utilisateurs mais aussi mobilité de l’infrastructure du réseau à laquelle ils contribuent. Ces réseaux se constituent de façon spontanée. Ils se maintiennent de manière autonome. On les désigne par le terme réseaux ad hoc mobiles (en anglais Mobile Ad hoc Networks ou MANET) qui s’oppose naturellement à celui de réseaux à infrastructure. La sécurité est une préoccupation générale des êtres humains. Ils en ressentent aussi le besoin en matière de réseaux. Ce besoin est particulièrement criant lorsque sont échangées des données critiques, financières ou stratégiques. La confidentialité des échanges, l’authentification des sources, l’assurance d’intégrité, la prévention de la récusation sont autant d’objectifs qu’il faut alors atteindre. Diverses solutions de sécurité ont été conçues dans cette optique pour les réseaux filaires puis ont ensuite été adaptées aux réseaux sans-fil et mobiles. Les architectures AAA (Authentication, Authorization, Accounting) en font partie. Elles sont en général utilisées dans un contexte commercial. Tant par leur facilité de déploiement que par la baisse des coûts de mise en œuvre qu’ils engendrent, les réseaux ad hoc mobiles, après avoir bien servi dans le domaine militaire, semblent avoir un avenir dans les applications commerciales. C’est pourquoi, nous nous proposons dans cette thèse de concevoir une architecture AAA adaptée aux spécificités de ces réseaux. Nous étudions d’abord les réseaux ad hoc mobiles et leurs caractéristiques. Ensuite, nous présentons les solutions de sécurité qui existent dans les réseaux à infrastructure. Nous examinons, en particulier, les solutions qui permettent le contrôle d’accès et dont sont engendrées les architectures AAA. Les solutions AAA proposées pour les MANETs sont par la suite analysées et classifiées afin de déterminer les manques et les vulnérabilités. Cette étude approfondie nous amène à proposer une architecture AAA répondant aux attentes identifiées. C’est une architecture distribuée qui répond, en particulier, au besoin d’autonomie des opérations dans les MANETs et où les protocoles exécutés peuvent impliquer simultanément plus de deux parties. Un ensemble de protocoles et de mécanismes d’authentification et d’autorisation s’intégrant avec la suite des protocoles IPv6 a été proposé. Leur sécurité a été discutée. Celle, en particulier du protocole d’authentification a fait l’objet de validation formelle. Contrairement aux protocoles utilisés dans la phase d’autorisation des services AAA proposés, le mode de communication multi-parties et multi-sauts du protocole d’authentification nous a poussé à mener une analyse approfondie de ses performances. Pour cela, nous avons eu recours, dans un premier temps, à la modélisation au moyen de calculs mathématiques explicites ensuite à la simulation. Les résultats obtenus montrent que ce protocole passe à l’échelle d’un MANET comprenant au moins cent nœuds. Dans certaines conditions d’implémentation que nous avons définies, ses performances, tant celle liée à sa probabilité de terminaison avec une issue favorable que celle portant sur son temps d’exécution, atteignent des valeurs optimales. / Mobility is an important component of people’s liberty. The evolution of technological means contributes to its enhancement. In addition to the transport issue, the question of keeping people connected is, in that context, particularly significant. Technological change strained the notion of telecommunications networks in the sense that scattered or clustered but mobile individuals had to remain in touch with others electronically. From the age of analogue networks to the digital networks era, from wired networks to wireless and mobile networks, technology has never stopped evolving. The last decades have witnessed the emergence of digital and wireless networks where not only the users, but also the network infrastructure to which they contribute, are mobile. These networks are spontaneously formed and autonomously maintained. They are termed Mobile Ad hoc Networks (MANETs), in contradistinction to infrastructure networks. Security is a general concern of human beings. They feel the need for it when using a network, too. This need is particularly glaring when it comes to exchanging critical, financial or strategic data. Confidentiality of communications, source authentication, integrity assurance, prevention of repudiation, are all objectives to be achieved. Various security solutions have been devised in this context as wired networks were then adapted to wireless and mobile networks. AAA (Authentication, Authorization and Accounting) frameworks are among these solutions. They are generally used for commercial purposes, which raises financial issues — and we all know how much important they are. Due to their ease of deployment and inexpensive implementation, MANETs, first used in the military field, seem to have a future in commercial applications. That is why the present thesis proposes to design an AAA service that is adapted to the characteristics of such networks. In this perspective, the thesis examines, to begin with, mobile ad hoc networks in order to understand their characteristics and potentials. It then probes the security solutions that exist in infrastructure networks, with special emphasis on those dealing with access control and AAA services. The AAA solutions for MANETs proposed up to now are subsequently analyzed and classified in order to determine their strengths and weaknesses. This in-depth study led to the design, in the second part of the thesis, of an AAA service that meets the expectations identified. It is a distributed service intended to answer the needs of autonomous operations in MANETs when a nearby operator is absent. It features several detailed authentication and authorization mechanisms and protocols with an authentication protocol simultaneously involving one or more parties. These protocols are designed such that they can be easily integrated to the IPv6 protocols suite. Moreover, their security is discussed — in particular, that of the authentication protocol thanks to a formal validation tool. Unlike the communication mode of the authorization protocols, that of the authentication protocol is one-to-many, which led us to study more deeply its performances thanks to modeling using explicit mathematical computations and to simulations techniques. The obtained results showed that the protocol scales for a MANET including a hundred nodes. Under certain conditions that we explained, its performances, in terms of the probability of authentication success and the length of the executing time, reach optimal values.

<p>With the constant development of wireless technologies, the usageof wireless devices tends to increase even more in the future.Wireless multi-hop networks (WMNs) have emerged as a keytechnology to numerous potential scenarios, ranging from disasterrecovery to wireless broadband internet access. The distributedarchitecture of WMNs enables nodes to cooperatively relay othernode's packets. Because of their advantages over other wirelessnetworks, WMNs are undergoing rapid progress and inspiringnumerous applications. However, many technical issues still existin this field. In this thesis we investigate how Voice over IP(VoIP) and peer-to-peer (P2P) application are influenced bywireless multi-hop network characteristics and how to optimizethem in order to provide scalable communication.We first consider the deployment of VoIP service in wirelessmulti-hop networks, by using the Session Initiation Protocol (SIP)architecture. Our investigation shows that the centralized SIParchitecture imposes several challenges when deployed in thedecentralized wireless multi-hop environment. We find that VoIPquality metrics are severely degraded as the traffic and number ofmultiple hops to the gateway increase. In the context ofscalability, we further propose four alternative approaches whichavoid current limitations.In the second part of this thesis we tackle the network capacityproblem while providing scalable VoIP service over wirelessmulti-hop networks. The performance evaluation shows the influenceof intra and inter-flow interference in channel utilization, whichdirect impacts the VoIP capacity. In order to avoid the small VoIPpacket overhead, we propose a new adaptive hop-by-hop packetaggregation scheme based on wireless link characteristics. Ourperformance evaluation shows that the proposed scheme can increasethe VoIP capacity by a two-fold gain.The study of peer-to-peer applicability over wireless multi-hopnetworks is another important contribution. A resource lookupapplication is realized through structured P2P overlay. We showthat due to several reasons, such as characteristics of wirelesslinks, multi-hop forwarding operation, and structured P2Pmanagement traffic aggressiveness the performance of traditionalP2P applications is rather low in wireless multi-hop environments.Therefore, we suggested that a trade-off between the P2P lookupefficiency and the P2P management traffic overhead can be achievedwhile maintaining the overlay network consistency in wirelessmulti-hop networks.</p>

Internet and mobile communications have had a profound effect on today's society. New services are constantly being deployed, in which personal data are being processed in return for personally tailored services. While mobile networks lay the groundwork for new innovative services, at the same time they pose numerous privacy challenges. There is the risk that honest citizens participating in mobile communications will have their privacy invaded for "the greater good". We argue that it is highly important that individuals are empowered to retain control over their personal spheres. Thus, the goal of this thesis is to design and evaluate anonymous overlay networks} adapted for mobile networks that allow users to control which information leaves their personal spheres in a mobile communication. Technically, by using an anonymous overlay network, users can communicate with their communication partners without disclosing their network identities. In this thesis, we propose three different anonymous overlay networks tailored for mobile networks. First, two approaches are proposed for anonymous browsing on the mobile Internet, namely mCrowds and a Tor-based approach. By applying theoretical analysis and\,/\,or practical experiments, we show that these approaches offer an appropriate trade-off between the offered degree of anonymity and performance loss. Second, an anonymous overlay network for use in mobile ad hoc networks - Chameleon - is suggested. Besides the actual design of these anonymous overlay networks, this thesis provides novel contributions in other essential areas of privacy protection and anonymous communication. First, also non-technical aspects of privacy protection are thoroughly discussed, including legal, social, and user interface aspects. Second, we survey existing metrics for quantifying anonymity and also propose new ideas regarding anonymity metrics. Third, we review and classify existing mechanisms for anonymous communication in mobile ad hoc networks. Lastly, we also propose a cryptographic technique for building up the user base of an anonymous overlay network in a secure and privacy-friendly manner.

Wireless communication has seen a tremendous growth in the last decades. Continuing on this trend, wireless multi-hop networks  are nowadays used or planned for use in a multitude of contexts, spanning from Internet access at home to emergency situations. The Transmission Control Protocol (TCP) provides reliable and ordered delivery of a data and is used by major Internet applications such as web browsers, email clients and file transfer programs. TCP traffic is also the dominating traffic type on the Internet. However, TCP performs less than optimal in wireless multi-hop networks due to packet reordering, low link capacity, packet loss and variable delay. In this thesis, we develop novel proposals for enhancing the network and transport layer to improve TCP performance in wireless multi-hop networks. As initial studies, we experimentally evaluate the performance of different TCP variants, with and without mobile nodes. We further evaluate the impact of multi-path routing on TCP performance and propose packet aggregation combined with aggregation aware multi-path forwarding as a means to better utilize the available bandwidth. The last contribution is a novel extension to multi-path TCP to  enable single-homed hosts to fully utilize the network capacity. / <p>Opponent changed. Prof. C. Lindeman from the University of Leipzig was substituted by Prof. Zhang.</p>

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.

Distributed systems like e-commerce and e-market places, peer-to-peer networks, social networks, and mobile ad hoc networks require cooperation among the participating entities to guarantee the formation and sustained existence of network services. The reliability of interactions among anonymous entities is a significant issue in such environments. The distributed entities establish connections to interact with others, which may include selfish and misbehaving entities and result in bad experiences. Therefore, trustworthiness evaluation using trust management techniques has become a significant issue in securing these environments to allow entities decide on the reliability and trustworthiness of other entities, besides it helps coping with defection problems and stimulating entities to cooperate. Recent models on evaluating trustworthiness in distributed systems have heavily focused on assessing trustworthiness of entities and isolate misbehaviours based on single trust metrics. Less effort has been put on the investigation of the subjective nature and differences in the way trustworthiness is perceived to produce a composite multidimensional trust metrics to overcome the limitation of considering single trust metric. In the light of this context, this thesis concerns the evaluation of entities’ trustworthiness by the design and investigation of trust metrics that are computed using multiple properties of trust and considering environment. Based on the concept of probabilistic theory of trust management technique, this thesis models trust systems and designs cooperation techniques to evaluate trustworthiness in mobile ad hoc networks (MANETs). A recommendation based trust model with multi-parameters filtering algorithm, and multidimensional metric based on social and QoS trust model are proposed to secure MANETs. Effectiveness of each of these models in evaluating trustworthiness and discovering misbehaving nodes prior to interactions, as well as their influence on the network performance has been investigated. The results of investigating both the trustworthiness evaluation and the network performance are promising.

The increasing growth of mobile devices in the whole world, and the forecasts for the coming years has been indicated by several reports. Nonetheless, this need for ubiquitous collaboration has brought new possibilities and challenges to the scientific community. Mobile Ad hoc Networks (MANETs) emerges in this scenario allowing devices to interconnect autonomously, without the need of a fixed infrastructure, in order to provide communication and information services. Due to such decentralization and the natural constraints of mobile devices, it remains, to this day, a challenge to provide efficient routing for MANETs. In this dissertation we propose new routing enhancements based on policies for MANETs running the HTR protocol. We consider the role(s) a user associated to a device performs within an organization. Hence our policies can guide the routing based on these roles. With this scheme we improve communication according to different business needs and scenario requirements. To this end, we propose a set of policies that affects the routing behavior and present four case studies to present each policy. Then we analyze two policies in terms of end-to-end delay, and nodes’ lifetime. Through simulation we evaluate these metrics while varying parameters such as the amount of nodes participating in the network, the mobility characteristics, and the number of traffic sources. Our results show that it is possible to achieve these goals without causing great impact on the average end-to-end delay and energy consumption, two important metrics in any MANET evaluation. We explore the results in several scenarios and detail our findings, which can provide a different perspective for future MANET applications. / Submitted by João Arthur Martins (joao.arthur@ufpe.br) on 2015-03-10T18:42:15Z No. of bitstreams: 2 Dissertação Gabriela Coutinho.pdf: 1701782 bytes, checksum: 113328c2efdd1ba97f7a237d03cab574 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-11T17:46:06Z (GMT). No. of bitstreams: 2 Dissertação Gabriela Coutinho.pdf: 1701782 bytes, checksum: 113328c2efdd1ba97f7a237d03cab574 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2013-09-13 / O crescimento das vendas de aparelhos móveis em todo o mundo, bem como as previsões para os próximos anos são apontadas em diversos relatórios. No entanto, essa necessidade de colaboração ubíqua trouxe novas possibilidades e desafios para a comunidade científica. Redes móveis ad hoc (Mobile Ad hoc Networks - MANETs) surgem diante deste cenário e permite que dispositivos se comuniquem de forma autônoma, sem a necessidade de uma infraestrutura predefinida para fornecer comunicação e serviços. Porém, essa descentralização junto com as restrições naturais dos dispositivos móveis, proporcionar roteamento eficiente para MANETs permanece um desafio. Este trabalho propõe novas melhorias para o roteamento em MANETs que utilizam o protocolo HTR. Também considera o papel que usuários associados aos dispositivos desempenham dentro de uma organização. Desta forma, as políticas desenvolvidas podem guiar o roteamento também com base nestes papéis. Com este esquema, é possível melhorar a comunicação de acordo com necessidades de negócio e requerimentos de cenário. Para este fim, esta dissertação propõe um conjunto de políticas que afetam o comportamento do roteamento e analisa os impactos em termos de atraso, energia gasta e tempo de vida dos nós. Através de simulações, essas métricas são avaliadas também com variação de parâmetros como a quantidade de nós que participam da simulação, as características de mobilidade e o número de fontes de tráfego. Resultados mostram que é possível atingir esses objetivos sem causar grande impacto negativo no atraso fim a fim e no consumo de energia, duas métricas importantes em avaliações de redes MANET. Nós exploramos esses resultados em diversos cenários e detalhamos nossas descobertas, que podem servir como uma perspectiva diferente para futuras aplicações de redes MANET.