Mobile social networking(MSN) has emerged as an effective platform for social network users to pervasively disseminate the contents such as news, tips, book information, music, video and so on. In content dissemination, mobile social network users receive content or information from their friends, acquaintances or neighbors, and selectively forward the content or information to others. The content generators and receivers have different motivation and requirements to disseminate the contents according to the properties of the contents, which makes it a challenging and meaningful problem to effectively disseminate the content to the appropriate users. In this dissertation, the typical content dissemination scenarios in MSNs are investigated. According to the content properties, the corresponding user requirements are analyzed. First, a Bayesian framework is formulated to model the factors that influence users behavior on streaming video dissemination. An effective dissemination path detection algorithm is derived to detect the reliable and efficient video transmission paths. Second, the authorized content is investigated. We analyze the characteristics of the authorized content, and model the dissemination problem as a new graph problem, namely, Maximum Weighted Connected subgraph with node Quota (MWCQ), and propose two effective algorithms to solve it. Third, the authorized content dissemination problem in Opportunistic Social Networks(OSNs) is studied, based on the prediction of social connection pattern. We then analyze the influence of social connections on the content acquirement, and propose a novel approach, User Set Selection(USS) algorithm, to help social users to achieve fast and accurate content acquirement through social connections.

The Publish/Subscribe (pub/sub) model has been widely applied in a variety of application scenarios which demand loose-coupling and asynchronous communication between a large number of information sources and sinks. In this model, clients are granted the flexibility to specify their interests at a high level and rely on the pub/sub middleware for delivery of their publications of interest. This increased flexibility and ease of use on the client side results in substantial complexity on part of the pub/sub middleware implementation. Furthermore, for several reasons including improved scalability, availability and avoiding a single point of failure, the pub/sub middleware is commonly composed of a set of collaborating message routers, a.k.a. brokers. The distributed nature of this design further introduces new challenges in ensuring end-to-end reliability as well as efficiency of operation. These challenges are largely unique to the pub/sub model and hence absent in both point-to-point or multicast protocols. This thesis develops solutions that ensure the dependable operation of the pub/sub system by exploiting the notion of overlay neighborhoods in a formal manner. More specifically, brokers maintain information about their neighbors within a configurable distance in the pub/sub overlay and exploit this knowledge to construct alternative forwarding paths or make smart forwarding decisions that improves efficiency, bandwidth utilization and delivery delay, all at the same time. Furthermore, in the face of failures overlay neighborhoods enable fast reconstruction of forwarding paths in the system without compromising its reliability and availability. Finally, as an added benefit of overlay neighborhoods, this thesis develops large-scale algorithms that bring the advantages of the pub/sub model to the domain of file sharing and bulk content dissemination applications. Experimental evaluation results with deployments as large as 1000 nodes illustrate that the pub/sub system scales well and outperforms the traditional BitTorrent protocol in terms of content dissemination delay.

The multifaceted utilization of mobile computing devices, including smart phones, PDAs, tablet computers with increasing functionalities and the advances in wireless technologies, has fueled the utilization of collaborative computing (peer-to-peer) technique in mobile environment. Mobile collaborative computing, known as mobile peer-to-peer (MP2P), can provide an economic way of data access among users of diversified applications in our daily life (exchanging traffic condition in a busy high way, sharing price-sensitive financial information, getting the most-recent news), in national security (exchanging information and collaborating to uproot a terror network, communicating in a hostile battle field) and in natural catastrophe (seamless rescue operation in a collapsed and disaster torn area). Nonetheless, data/content dissemination among the mobile devices is the fundamental building block for all the applications in this paradigm. The objective of this research is to propose a data dissemination scheme for mobile distributed systems using an MP2P technique, which maximizes the number of required objects distributed among users and minimizes to object acquisition time. In specific, we introduce a new paradigm of information dissemination in MP2P networks. To accommodate mobility and bandwidth constraints, objects are segmented into smaller pieces for efficient information exchange. Since it is difficult for a node to know the content of every other node in the network, we propose a novel Spatial-Popularity based Information Diffusion (SPID) scheme that determines urgency of contents based on the spatial demand of mobile users and disseminates content accordingly. The segmentation policy and the dissemination scheme can reduce content acquisition time for each node. Further, to facilitate efficient scheduling of information transmission from every node in the wireless mobile networks, we modify and apply the distributed maximal independent set (MIS) algorithm. We also consider neighbor overlap for closely located mobile stations to reduce duplicate transmission to common neighbors. Different parameters in the system such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in an MP2P environment. We have developed analytical models for our proposed scheme for object diffusion time/delay in a wireless mobile network to apprehend the interrelationship among these different parameters. In specific, we present the analytical model of object propagation in mobile networks as a function of node densities, radio range, and node speed. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we construct an analytical model based on the Markov process to estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in wireless mobile networks considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in mobile networks.

The Publish/Subscribe (pub/sub) model has been widely applied in a variety of application scenarios which demand loose-coupling and asynchronous communication between a large number of information sources and sinks. In this model, clients are granted the flexibility to specify their interests at a high level and rely on the pub/sub middleware for delivery of their publications of interest. This increased flexibility and ease of use on the client side results in substantial complexity on part of the pub/sub middleware implementation. Furthermore, for several reasons including improved scalability, availability and avoiding a single point of failure, the pub/sub middleware is commonly composed of a set of collaborating message routers, a.k.a. brokers. The distributed nature of this design further introduces new challenges in ensuring end-to-end reliability as well as efficiency of operation. These challenges are largely unique to the pub/sub model and hence absent in both point-to-point or multicast protocols. This thesis develops solutions that ensure the dependable operation of the pub/sub system by exploiting the notion of overlay neighborhoods in a formal manner. More specifically, brokers maintain information about their neighbors within a configurable distance in the pub/sub overlay and exploit this knowledge to construct alternative forwarding paths or make smart forwarding decisions that improves efficiency, bandwidth utilization and delivery delay, all at the same time. Furthermore, in the face of failures overlay neighborhoods enable fast reconstruction of forwarding paths in the system without compromising its reliability and availability. Finally, as an added benefit of overlay neighborhoods, this thesis develops large-scale algorithms that bring the advantages of the pub/sub model to the domain of file sharing and bulk content dissemination applications. Experimental evaluation results with deployments as large as 1000 nodes illustrate that the pub/sub system scales well and outperforms the traditional BitTorrent protocol in terms of content dissemination delay.

The multifaceted utilization of mobile computing devices, including smart phones, PDAs, tablet computers with increasing functionalities and the advances in wireless technologies, has fueled the utilization of collaborative computing (peer-to-peer) technique in mobile environment. Mobile collaborative computing, known as mobile peer-to-peer (MP2P), can provide an economic way of data access among users of diversified applications in our daily life (exchanging traffic condition in a busy high way, sharing price-sensitive financial information, getting the most-recent news), in national security (exchanging information and collaborating to uproot a terror network, communicating in a hostile battle field) and in natural catastrophe (seamless rescue operation in a collapsed and disaster torn area). Nonetheless, data/content dissemination among the mobile devices is the fundamental building block for all the applications in this paradigm. The objective of this research is to propose a data dissemination scheme for mobile distributed systems using an MP2P technique, which maximizes the number of required objects distributed among users and minimizes to object acquisition time. In specific, we introduce a new paradigm of information dissemination in MP2P networks. To accommodate mobility and bandwidth constraints, objects are segmented into smaller pieces for efficient information exchange. Since it is difficult for a node to know the content of every other node in the network, we propose a novel Spatial-Popularity based Information Diffusion (SPID) scheme that determines urgency of contents based on the spatial demand of mobile users and disseminates content accordingly. The segmentation policy and the dissemination scheme can reduce content acquisition time for each node. Further, to facilitate efficient scheduling of information transmission from every node in the wireless mobile networks, we modify and apply the distributed maximal independent set (MIS) algorithm. We also consider neighbor overlap for closely located mobile stations to reduce duplicate transmission to common neighbors. Different parameters in the system such as node density, scheduling among neighboring nodes, mobility pattern, and node speed have a tremendous impact on data diffusion in an MP2P environment. We have developed analytical models for our proposed scheme for object diffusion time/delay in a wireless mobile network to apprehend the interrelationship among these different parameters. In specific, we present the analytical model of object propagation in mobile networks as a function of node densities, radio range, and node speed. In the analysis, we calculate the probabilities of transmitting a single object from one node to multiple nodes using the epidemic model of spread of disease. We also incorporate the impact of node mobility, radio range, and node density in the networks into the analysis. Utilizing these transition probabilities, we construct an analytical model based on the Markov process to estimate the expected delay for diffusing an object to the entire network both for single object and multiple object scenarios. We then calculate the transmission probabilities of multiple objects among the nodes in wireless mobile networks considering network dynamics. Through extensive simulations, we demonstrate that the proposed scheme is efficient for data diffusion in mobile networks.

Peer-to-peer swarming, as used by BitTorrent, is one of the de facto solutions for content dissemination in today’s Internet. By leveraging resources provided by users, peer-to-peer swarming is a simple, scalable and efficient mechanism for content distribution. Although peer-to-peer swarming has been widely studied for a decade, prior work has focused on the dissemination of one commodity (a single file). This thesis focuses on the multi-commodity case. We have discovered through measurements that a vast number of publishers currently disseminate multiple files in a single swarm (bundle). The first contribution of this thesis is a model for content availability. We use the model to show that, when publishers are intermittent, bundling K files increases content availability exponentially as function of K. When there is a stable publisher, we consider content availability among peers (excluding the publisher). Our second contribution is the estimate of the dependency of peers on the stable publisher, which is useful for provisioning purposes as well as in deciding how to bundle. To this goal, we propose a new metric, swarm self-sustainability, and present a model that yields swarm self-sustainability as a function of the file size, popularity and service capacity of peers. Then, we investigate reciprocity and the use of barter that occurs among peers. As our third contribution, we prove that the loss of efficiency due to the download of unrequested content to enforce direct reciprocity, as opposed to indirect reciprocity, is at most two in a class of networks without relays. Finally, we study algorithmic and economic problems faced by enterprises who leverage swarming systems and who control prices and bundling strategies. As our fourth contribution, we present two formulations of the optimal bundling problem, and prove that one is NP hard whereas the other is solvable by a greedy strategy. From an economic standpoint, we present conditions for the existence and uniqueness of an equilibrium between publishers and peers.

Les réseaux véhiculaires constituent une catégorie de réseaux sans fil mobiles à part entière et présentent l'originalité de permettre aux véhicules de communiquer les uns avec les autres mais aussi avec l'infrastructure quand elle existe. L'apparition des réseaux véhiculaires s'est accompagnée de l'apparition d'une myriade et variété d'applications potentielles allant de la sécurité à la gestion du trafic routier en passant par les applications de divertissement et de confort des usagers de la route. Ces applications ont suscité beaucoup d'intérêt de la part des chercheurs, des constructeurs des automobiles et des opérateurs des télécommunications. Les applications d'information et de divertissement, pour lesquelles une grande quantité de contenus peut exister, exigent que les contenus engendrés soient propagés au travers des véhicules et/ou de l'infrastructure jusqu'à atteindre les utilisateurs intéressés tout en respectant les durées de vie potentiellement limitées des contenus. La dissémination de contenus pour ce type d'applications reste un défi majeur en raison de plusieurs facteurs tels que la présence de beaucoup de contenus, la connectivité très intermittente mais encore les intérêts potentiellement hétérogènes des utilisateurs. C'est à cette thématique que nous sommes intéressés dans cette thèse; Tout d'abord, nous nous proposons une nouvelle métrique qui calcule l'utilité apportée aux utilisateurs. Elle permet de mesurer leur satisfaction par rapport aux contenus reçus. Nous la jugeons nécessaire pour évaluer les performances d'une approche de dissémination pour les applications de confort par opposition à des applications de sécurité routière. Dans un deuxième temps, nous nous concentrons sur le développement d'un nouveau protocole de dissémination, appelé I-PICK, et d'une solution de sélection des nœuds relais, appelé I-SEND, pour disséminer les contenus d'information et de divertissement en tenant compte des préférences des utilisateurs par rapport aux contenus reçus. Notre proposition est fondée sur l'échange de messages périodiques permettant l'estimation des durées de contacts et la connaissance des préférences des utilisateurs. Ces informations sont ensuite utilisées, dans un premier temps, pour effectuer un ordonnancement efficace des contenus lors de la dissémination puis choisir les relais permettant de maximiser l'utilité des utilisateurs par rapport aux contenus reçus dans un environnement caractérisé par des faibles durées de communication. Au travers de simulations nous confirmons l'efficacité de notre approche. Pour conforter le fonctionnement de nos mécanismes, nous avons implanté dans un environnement réel nos propositions I-PICK et I-SEND. Au travers d'un scénario simple, nous avons mis en évidence des risques liés à l'hétérogénéité des machines ou bien encore la difficulté du paramétrage des temporisations. Ces premiers résultats positifs montrent l'intérêt de notre technique et ouvre des pistes d'amélioration. Notre dernière contribution concerne des mécanismes de réduction du trafic cellulaire à l'aide des communications opportunistes entre les véhicules. Quand un contenu est disponible auprès d'un serveur de contenus accessible par le réseau cellulaire, il est nécessaire de proposer une méthode efficace de sélection des sources initiales qui seront choisies pour télécharger puis disséminer les contenus. Nous optons pour une solution qui pourrait reposer sur technologie SDN ainsi que sur des communications opportunistes et qui permet de choisir les sources en tant que nœuds pouvant produire un maximum d'utilité en propageant les contenus. / Vehicular networks are a class of mobile wireless networks and have the originality of enabling vehicles to communicate with each other and also with the infrastructure when it exists. The advent of vehicular networks has been accompanied by the emergence of a myriad and a variety of potential applications that are not only restricted to road safety but span from traffic management to entertainment and comfort applications. These applications have received much interest from researchers, automobile manufacturers, and telecommunications operators. Information and entertainment applications, where a large amount of content can exist, require the dissemination of the generated content through vehicles and/or infrastructure until reaching interested users while respecting the potential limited lifetime of content. The content dissemination for this type of applications remains a major challenge due to several factors such as the presence of a large amount of content, an intermittent connectivity, and the heterogeneous interests of users. In this thesis we turn our attention to this topic. First, we propose a new metric that allows to measure the users satisfaction with respect to the received content. This metric is used to evaluate the performance of the dissemination schemes. Second, we focus on the development of a new dissemination protocol, named I-PICK, and a forwarder selection solution, named I-SEND, to disseminate information and entertaining content in vehicular networks while ensuring maximum satisfaction of the users preferences with respect to the received content. Our proposal is based on the exchange of periodic messages enabling the estimation of contact durations and the knowledge of user preferences. First of all, this information is used to conduct an efficient content scheduling during the dissemination, and then to select relay nodes for maximizing the utility to users. We confirm the efficiency of our approach through simulations. To strengthen the functioning of our mechanisms, we implemented our proposals I-PICK and I-SEND in a real environment. Through a simple scenario, we have highlighted the risks associated with the heterogeneity of the machines and even the difficulty of setting timers. These first positive results show the interest of our solutions and raise new questions to be addressed. Our last contribution concerns cellular traffic offloading schemes by exploiting vehicular opportunistic communications. We study the seed-vehicles selection problem as the first step toward bootstrapping cellular traffic offloading for content dissemination in vehicular networks. We propose a solution that takes advantage from the presence of the SDN technology as well as vehicular opportunistic communications to select as seeds the nodes that can produce maximum utility when propagating the content.