Approved for public release; distribution in unlimited. / In spite of the fact that wireless network technology has been available for long period of time, there has been very limited wireless networks deployments around the world before 1997 due to the lack of widely recognized standard for wireless networks. Thanks to the approval of the IEEE 802.11 family of standards in 1997, the world has witnessed tremendous deployment and proliferation of wireless networks in all aspects of life. Although the IEEE 802.11 family of standards has been ratified to design radio transceivers for wireless computer stations capable of interconnecting with other wireless computer stations in close proximity, the technology has been successfully employed to design and implement wireless networks with great number of distant wireless computer stations with reasonable data throughput and flexibility. This thesis explores the wireless network technology and the primary building blocks and components of a wireless network. It also explores the IEEE 802.11 standard and its technical specifications including the Physical layer (PHY), the Media Access Control layer (MAC) and the ongoing task forces. Additionally, the thesis examines the wireless network security including the vulnerabilities, ongoing improvements and recommendations. Next, it investigates the market for available wireless devices compatible with the IEEE 802.11 standard that can be used to build a wireless network with high data throughput and high level of security. Subsequently, the thesis formulates a design plan for civilian wireless network with different scenarios in order to provide a speedy solution to the limited broadband service availability in the Sultanate of Oman. Additionally, the thesis formulates a generic design plan for a military wireless network with different scenarios that can be rapidly deployed in the field of operations. / Computer Engineer, Royal Army of Oman

The rapid expansion of wireless information technology (IT) coupled with a dramatic increase in security breaches forces organizations to develop comprehensive strategies for managing security risks. The problem addressed was the identification of security risk management practices and human errors of IT administrators, putting the organization at risk for external security intrusion. The purpose of this non-experimental quantitative study was to investigate and determine the security risk assessment practices used by IT administrators to protect the confidentiality and integrity of the organization's information. The research questions focused on whether the security risk management practices of IT administrators met or exceeded the minimally accepted practices and standards for wireless networking. The security risk assessment and management model established the theoretical framework. The sample was 114 participants from small to medium IT organizations comprised of security engineers, managers, and end users. Data collection was via an online survey. Data analysis included both descriptive and inferential statistical methods. The results revealed that greater than 80% of participants conducted appropriate risk management and review assessments. This study underscored the need for a more comprehensive approach to managing IT security risks. IT managers can use the outcome of this study as a benchmark for evaluating their current risk assessment procedures. Experiencing security breaches in organizations may be inevitable. However, when organizations and industry leaders can greatly reduce the cost of a data breach by developing effective risk management plans that lead to better security outcomes, positive social change can be realized.

Fin 2004, un quart des foyers Européens étaient connectés à l'Internet haut débit. Avec le faible coût des machines toujours plus puissantes, de nombreuses applications multimédias ont pu être élaborées pour satisfaire la demande croissante du grand public. Le besoin d'adaptation des protocoles de communication sous-jacents est essentiel pour ce type d'applications. Les protocoles doivent pouvoir passer à l'échelle et s'adapter aux caractéristiques hétérogènes de ces nouvelles applications. Parallèlement, les transmissions sans fil ont connu un essor sans égal, permettant un accès à l'Internet de n'importe quel endroit. La multiplicité des technologies d'accès (GPRS, UMTS, WIFI, WiMAX, Bluetooth, etc.) et la grande variabilité des caractéristiques des canaux de transmission sans fil ont encore accru ce besoin d'adaptation. Dans ce document d'habilitation, je présente quatre contributions qui mettent en relief le besoin d'adaptation des protocoles de communication. La première concerne un protocole de communication robuste au facteur d'échelle élaboré pour des applications d'environnements virtuels qui mettent en jeu un grand nombre de participants. La seconde décrit un algorithme pour contrôler la transmission de vidéo hiérarchique vers un ensemble hétérogène de récepteurs sur Internet. Les deux contributions suivantes portent sur la transmission<br />sans fil. Je décris un mécanisme de différenciation de services efficace pour transmettre des flots multimédias à débit variable dans les réseaux IEEE 802.11e, ainsi qu'un mécanisme d'adaptation intercouches pour la transmission multimédia dans les réseaux WIFI.

L'un des défis majeurs dans la convergence des réseaux et des services vers la technologie IP est le maintien de la qualité de service (QoS) des flux audio/vidéo transmis sur des réseaux sans fil pour des utilisateurs mobiles et hétérogènes. Dans cet environnement, les services multimédia doivent faire face à plusieurs inconvénients engendrés par le manque de fiabilité d'un canal sans fil et son partage par plusieurs utilisateurs. Ces inconvénients sont accentués par l'hétérogénéité des terminaux de réception (capacité de décodage, espace de stockage, résolution d'affichage, etc.) qui doivent recevoir, décoder et afficher les flux multimédia.<br />Afin d'assurer un accès universel aux services n' importe où, n'importe quand et en utilisant n'importe quel terminal d'accès, les applications multimédia de nouvelle génération doivent interagir avec leur environnement pour, d'une part, informer les réseaux sous-jacents de leur besoins en QoS, et d'autre part, adapter dynamiquement leurs services en fonction des terminaux de réception et des variations intempestives des conditions de transmission. <br />Dans ce contexte, nous proposons un nouveau système pour la transmission des flux audio/vidéo sur les réseaux 802.11 basé sur l'approche Cross-layer. Ce nouveau système, appelé XLAVS (Cross Layer Adaptive Video Streaming), communique activement avec l'ensemble des couches réseaux ainsi que le récepteur final pour déterminer l'adaptation optimale qui permet d'optimiser la QoS des flux audio/vidéo. <br />Nos contributions se focalisent principalement sur les adaptations Cross-layer mises en œuvre par le XLAVS. Ces contributions sont organisées en deux grandes catégories : les adaptations ascendantes exécutées au niveau applicatif et les adaptations descendantes exécutées au niveau MAC 802.11.<br />Dans la première catégorie, notre apport s'articule au tour de : (1) l'adaptation dynamique du débit vidéo en fonction du débit physique disponible dans le réseau 802.11 et (2) l'adaptation conjointe du taux de redondance FEC et du débit vidéo contrôlée par la puissance du signal et les taux de perte. <br />Dans la deuxième catégorie, nous proposons deux mécanismes Cross-layer au niveau MAC 802.11 : (1) une fragmentation 802.11 adaptative pour trouver un compromis entre les pertes de paquets et l'overhead introduit par les couches 802.11 et (2) un groupage des images vidéo au niveau MAC pour permettre au flux vidéo d'avoir un accès au canal 802.11 proportionnel à son débit.

Cette thèse a été motivée par le nouveau contexte ubiquitaire des réseaux ambiants sans-fil. Les protocoles Internet ont été conçus il y a 30 ans sans prendre en considération l'usage nomade des réseaux et ne répondent pas aux nouvelles contraintes de la mobilité. Notre but a été de concevoir des mécanismes pour rendre la mobilité transparente aux applications et utilisateurs. Une partie de notre travail a été axé sur l'amélioration du délai du handoff au niveau physique 802.11 à quelques dizaines de millisecondes. Le déplacement des hôtes et le changement de réseau demandent souvent une reconfiguration des plusieurs paramètres au niveau IP. Dans le cas d'une mobilité locale, l'approche que nous avons choisi est de permettre aux hôtes de garder inchangées leurs adresses et de mettre en place des routes d'hôte dans le domaine local. Au contraire, pour la mobilité globale, le routage optimal à travers l'Internet nous oblige de concevoir une solution dans laquelle les hôtes mobiles changent leurs adresses IP, en conformité avec le réseau ou ils s'y trouvent. Notre solution est basée sur le principe général « de bout en bout » dans laquelle les deux hôtes impliquées dans une connexion sont les seuls à assurer le transfert de cette connexion aux nouveaux points d'attachement. Elle utilise l'interception des appels de la bibliothèque socket et des requêtes DNS ainsi que la translation locale d'adresses pour virtualiser les adresses IP réelles dans des identificateurs d'hôte stables présentés aux niveaux supérieurs.

<p>In future mobile networks service quality might be poor. A new measure is needed to be able to assess services in terms of their effectiveness and usefulness despite their lacking visual appeal. Cognitive Quality of Service is a way to measure the effectiveness in use of a networked service.</p><p>This thesis introduces Cognitive Quality of Service and puts it in relation to other ways to measure quality in streaming media. Through four studies the concept is used to improve multicast performance in a WLAN, to assess the effectiveness of simple animations compared to video, to build an application that fuses video and animations and to assess the differences between various levels of streaming video quality.</p><p>Guidelines on how to measure Cognitive Quality of Service are introduced based on a review of available literature and later analyzed in light of the studies presented in the thesis. It turns out that the guidelines are sound and should be used as a basis for assessing Cognitive Quality of Service.</p><p>Finally, the usefullness of Cognitive Quality of Service is analyzed. It turns out that it is especially useful when comparing different media, e.g. animations and video. In the video only case even bit-rate might be a useful predictor of subjective quality.</p> / <p>I framtiden kommer användare att titta på videosekvenser i trådlösa apparater, exempelvis mobiltelefoner. På grund av tekniska faktorer som störningar och på grund av kostnaden för det kommer den kvalitet som de erhåller inte att vara jämförbar med till exempel den kvalitet som kan erhållas när man tittar på tv. Trots det kan man anta att sådan video kan vara intressant och upplysande.</p><p>I avhandlingen introduceras och används begreppet Cognitive Quality of Service (CQoS) - kognitiv servicekvalitet. Begreppet definieras av att den överföring som ger den bästa förståelsen och känslomässiga reaktionen också har bäst CQoS. För att mäta CQoS bör man följa vissa riktlinjer, särskilt som det är svårt att mäta förståelse i samband med att man tittar på video.</p><p>Författaren har tillsammans med medarbetare tittat på hur man kan förbättra förhållandena för själva radioöverföringen (studie I). Genom en algoritm som ger multicast-paket bättre skydd mot kollisioner visas att man kan erhålla förbättrad överföringskapacitet för strömmande video i ett trådlöst nätverk.</p><p>Animeringar är ett alternativ till video som kräver låg bandbredd. I ett experiment har man undersökt hur väl animeringar står sig mot video av olika kvalitet när det gäller att upplysa användaren och ge en bra upplevelse (studie II). Det visade sig att animeringar var bättre för förståelsen medan video gav en bättre känslomässig upplevelse. Vanare åskådare föredrog videon medan ovanare åskådare föredrog animeringarna.</p><p>Frågan som ställdes var då hur man kunde kombinera respektive mediums fördelar för att få en så bra blandning som möjligt. Å ena sidan var animeringarna billiga och lätta att förstå medan videon var dyrare och mer intressant. Ett prototypgränssnitt skapades. Där kunde användaren själv välja vilken mix mellan de två alternativen som skulle visas (studie III). Det visade sig att försökspanelen föredrog video och dessutom ville ha mer information om spelare och match.</p><p>Trots animationernas förträfflighet kan man anta att det ändå är video som kommer att dominera i framtiden. En sista studie genomfördes för att se om man kunde finna liknande resultat vid olika kvalitetsgrader i video som man tidigare hade funnit mellan video och animeringar (studie IV). Det visade sig att så länge man höll sig till ett format var sambanden enklare. Mer var helt enkelt bättre upp till en viss gräns där det inte tillförde mer att öka överföringsresurserna för videon.</p><p>Sammanfattningsvis visar studierna att CQoS kan ge värdefull designkunskap. I synnerhet när man jämför olika presentationsformer som i det här fallet animeringar och video. Nästa steg blir att gå vidare med att applicera CQoS i tvåvägskommunikation, särskilt i Conversational Multimedia (CMM)– ungefär bildtelefoni – där det är särskilt goda möjligheter att sammanställa en för omständigheterna anpassad mediamix.</p>

La presente tesis doctoral contribuye a la incesante evolución de las comunicaciones inalámbricas. Se centra en el diseño de protocolos de acceso al medio (MAC) para redes ad hoc y redes inalámbricas cooperativas. En una primera parte introductoria se presenta un minucioso estado del arte y se establecen las bases teóricas de las contribuciones presentadas en la tesis. En esta primera parte introductoria se definen las principales motivaciones de la tesis y se plantean los objetivos. Después, las contribuciones de la tesis se organizan en dos grandes bloques, o partes. En la primera parte de esta tesis se diseña, analiza y evalúa el rendimiento de un novedoso protocolo MAC de alta eficiencia llamado DQMAN (Protocolo MAC basado en colas distribuidas para redes ad hoc). Este protocolo constituye la extensión y adaptación del protocolo DQCA, diseñado para redes centralizadas, para operar en redes sin infraestructura. En DQMAN se introduce un nuevo paradigma en el campo del acceso al medio para redes distribuidas: la integración de un algoritmo de clusterización espontáneo y dinámico basado en una estructura de master y esclavo junto con un protocolo MAC de alta eficiencia diseñado para redes centralizadas. Tanto el análisis teórico como las simulaciones por ordenador presentadas en esta tesis muestran que DQMAN mejora el rendimiento del actual estándar IEEE 802.11. La principal característica de DQMAN es que se comporta como un protocolo de acceso aleatorio cuando la carga de tráfico es baja y cambia automática y transparentemente a un protocolo de reserva a medida que el tráfico de la red aumenta. Además, su rendimiento es prácticamente independiente del número de usuarios simultáneos de la red, lo cual es algo deseable en redes que nacen para cubrir una necesidad espontánea y no pueden ser planificadas. El hecho de que algoritmo de clusterización se base en un acceso aleatorio permite la coexistencia e intercomunicación de usuarios DQMAN con usuarios basados en el estándar IEEE 802.11. Este estudio se presenta en esta primera parte de la tesis y es fundamental de cara a una posible explotación comercial de DQMAN. La metodología presentada en esta tesis mediante el cual se logra extender la operación de DQCA a entornos ad hoc sin infraestructura puede ser utilizada para adaptar cualquier otro protocolo centralizado. Con el objetivo de poner de manifiesto esta realidad, la primera parte de la tesis concluye con el diseño y evaluación de DPCF como una extensión distribuida del modo de coordinación centralizado (PCF) del estándar IEEE 802.11 para operar en redes distribuidas. La segunda parte de la tesis se centra en el estudio de un tipo específico de técnicas cooperativas: técnicas cooperativas de retransmisión automática (C-ARQ). La idea principal de las técnicas C-ARQ es que cuando un paquete de datos se recibe con bits erróneos, se solicita retransmisión, no a la fuente de datos, si no a cualquiera de los usuarios que escuchó la transmisión original. Estos usuarios se convierten en espontáneos retransmisores que permiten mejorar la eficiencia de la comunicación. A pesar de que este tipo de esquema puede obtener diversidad de cooperación, el hecho de implicar a más de un usuario en una comunicación punto a punto requiere una coordinación que hasta ahora ha sido obviada en la literatura, asumiendo que los retransmisores pueden coordinarse perfectamente para retransmitir uno detrás de otro. En esta tesis se analiza y evalúa el coste de coordinación impuesto por la capa MAC y se identifican los principales retos de diseño que las técnicas C-ARQ imponen al diseño de la capa MAC. Además, se presenta el diseño y análisis de dos novedosos protocolos MAC para C-ARQ: DQCOOP y PRCSMA. El primero se basa en DQMAN y constituye una extensión de este para operar en esquemas C-ARQ, mientras que el segundo constituye la adaptación del estándar IEEE 802.11 para poder ejecutarse en un esquema C-ARQ. El rendimiento de estos esquemas se compara en esta tesis tanto con esquemas no cooperativos como con esquemas ideales cooperativos donde se asume que el MAC es ideal. Los resultados principales muestran que el diseño eficiente de la capa MAC es esencial para obtener todos los beneficios potenciales de los esquemas cooperativos. / This thesis aims at contributing to the incessant evolution of wireless communications. The focus is on the design of medium access control (MAC) protocols for ad hoc and cooperative wireless networks. A comprehensive state of the art and a background on the topic is provided in a first preliminary part of this dissertation. The motivations and key objectives of the thesis are also presented in this part. Then, the contributions of the thesis are divided into two fundamental parts. The first part of the thesis is devoted to the design, analysis, and performance evaluation of a new high-performance MAC protocol. It is the Distributed Queueing MAC Protocol for Ad hoc Networks (DQMAN) and constitutes an extension and adaptation of the near-optimum Distributed Queueing with Collision Avoidance (DQCA) protocol, designed for infrastructure-based networks, to operate over networks without infrastructure. DQMAN introduces a new access paradigm in the context of distributed networks: the integration of a spontaneous, dynamic, and soft-binding masterslave clustering mechanism together with a high-performance infrastructure-based MAC protocol. Theoretical analysis and computer-based simulation show that DQMAN outperforms IEEE 802.11 Standard. The main characteristic of the protocol is that it behaves as a random access control protocol when the traffic load is low and it switches smoothly and automatically to a reservation protocol as the traffic load grows. In addition, its performance is almost independent of the number of users of a network. The random-access based clustering algorithm allows for the coexistence and intercommunication of stations using DQMAN with the ones just based on the legacy IEEE 802.11 Standard. This assessment is also presented in this first part of the dissertation and constitutes a key contribution in the light of the commercial application of DQMAN. Indeed, the rationale presented in this first part of the thesis to extend DQCA and become DQMAN to operate over distributed networks can be used to extend the operation of any other infrastructure-based MAC protocol to ad hoc networks. In order to exemplify this, a case study is presented to conclude the first part of the thesis. The Distributed Point Coordination Function (DPCF) MAC protocol is presented as the extension of the PCF of the IEEE 802.11 Standard to be used in ad hoc networks. The second part of the thesis turns the focus to a specific kind of cooperative communications: Cooperative Automatic Retransmission Request (C-ARQ) schemes. The main idea behind C-ARQ is that when a packet is received with errors at a receiver, a retransmission can be requested not only from the source but also to any of the users which overheard the original transmission. These users can become spontaneous helpers to assist in the failed transmission by forming a temporary ad hoc network. Although such a scheme may provide cooperative diversity gain, involving a number of users in the communication between two users entails a complicated coordination task that has a certain cost. This cost has been typically neglected in the literature, assuming that the relays can attain a perfect scheduling and transmit one after another. In this second part of the thesis, the cost of the MAC layer in C-ARQ schemes is analyzed and two novel MAC protocols for C-ARQ are designed, analyzed, and comprehensively evaluated. They are the DQCOOP and the Persistent Relay Carrier Sensing Multiple Access (PRCSMA) protocols. The former is based on DQMAN and the latter is based on the IEEE 802.11 Standard. A comparison with non-cooperative ARQ schemes (retransmissions performed only from the source) and with ideal CARQ (with perfect scheduling among the relays) is included to have actual reference benchmarks of the novel proposals. The main results show that an efficient design of the MAC protocol is crucial in order to actually obtain the benefits associated to the C-ARQ schemes.

The C2X Communication is of high interest to the automotive industry. Ongoing research on this topic mainly bases on the simulation of Vehicular Ad Hoc Networks. In order to estimate the necessary level of simulation details their impact on the results needs to be examined. This thesis focuses on different channel models as the freespace, shadowing, and Ricean model, along with varying parameters. For these simulations the network simulator ns-2 is extended to provide IEEE 802.11p compliance. However, the WAVE mode is not considered since it is still under development and not finally approved. Besides a more sophisticated packet error model than the existing implementation, as well as a link adaptation algorithm, is added. In this thesis several simulations examine specific details of wireless communication systems such as fairness of multiple access, interferences, throughput, and variability. Furthermore, the simulation points out some unexpected phenomena as starving nodes and saturation effects in multi hop networks. Those led to the conclusion that the IEEE 802.11 draft amendment does not solve known problems of the original IEEE 802.11 standard.

M. Tech. Electrical Engineering. / Presents an IPv6-based mobility support scheme for vehicular scenarios. The focus of this study is on modelling of an efficient network layer handover scheme suitable for vehicular network environments. In order to achieve this, a Vehicular Fast handovers for Mobile IPv6 (VFMIPv6) network layer protocol has been proposed.

Mobility management over heterogeneous wireless networks is becoming a major interest area as new technologies and services continue to proliferate within the wireless networking market. In this context, seamless mobility is considered to be crucial for ubiquitous computing. Service providers aim to increase the revenue and to improve users' satisfaction. However there are still many technical and architectural challenges to overcome before achieving the required interoperability and coexistence of heterogeneous wireless access networks. Indeed, the context of wireless networks is offering multiple and heterogeneous technologies (e.g. 2G to 4G, WiFi, Wimax, TETRA,...). On the one hand, this rich environment allows users to take profit from different capacities and coverage characteristics. Indeed, this diversity can provide users with high flexibility and allow them to seamlessly connect at any time and any where to the access technology that best fits their requirements. Additionally, cooperation between these different technologies can provide higher efficiency in the usage of the scarce wireless resources offering more economic systems for network providers. On the other hand, the heterogeneity of technologies and architectures and the multiplication of networks and service providers creates a complex environment where cooperation becomes challenging at different levels including and not limited to mobility management, radio resource provisioning, Quality of Service and security guarantees. This thesis is focusing on mobility management and mainly on decision making for Vertical handover within heterogeneous wireless network environments. After the analysis of the related state of the art, we first propose a reputation based approach that allows fast vertical handover decision making. A decision making scheme is then built on that approach. Network's reputation, is a new metric that can be gathered from previous users' experiences in the networks. We show that it is an efficient construct to speed up the vertical handover decision making thanks to anticipation functionalities. While the main objective remains guaranteeing the best Quality of Service and optimal radio resource utilization, economical aspects have also to be considered including cost minimization for users and revenue maximization for network providers. For this aim, we propose, in the second part of the thesis, a game theoretic based scheme that allows maximizing benefits for both networks and users. In this solution, each available network plays a Stackelberg game with a finite set of users, while users are playing a Nash game among themselves to share the limited radio resources. A Nash equilibrium point, that maximizes the user's utility and the service provider revenue, is found and used for admission control and vertical handover decision making. The analyses of the optimal bandwidth/prices and the revenue at the equilibrium point show that there are some possible policies to use according to user's requirements in terms of QoS and to network capacities. For instance, we pointed out that networks having same capacities and different reputation values should charge users with different prices which makes reputation management very important to attract users and maximize networks' revenue. In the third part of this thesis, we provide and discuss two different architectural and implementation solutions on which our proposed vertical handover decision mechanisms can be integrated. The first proposed architecture is a centralized one. It is based on the IEEE 802.21 standard to which some extensions are proposed. The second proposed architecture is distributed. It is based on an overlay control level composed of two virtualization layers able to make reasoning on behalf of physical entities within the system. This architecture allows higher flexibility especially for loosely coupled interconnected networks