Towards efficacy and efficiency in sparse delay tolerant networks

The ubiquitous adoption of portable smart devices has enabled a new way of communication via Delay Tolerant Networks (DTNs), whereby messages are routed by the personal devices carried by ever-moving people. Although a DTN is a type of Mobile Ad Hoc Network (MANET), traditional MANET solutions are ill-equipped to accommodate message delivery in DTNs due to the dynamic and unpredictable nature of people\u27s movements and their spatio-temporal sparsity. More so, such DTNs are susceptible to catastrophic congestion and are inherently chaotic and arduous. This manuscript proposes approaches to handle message delivery in notably sparse DTNs. First, the ChitChat system [69] employs the social interests of individuals participating in a DTN to accurately model multi-hop relationships and to make opportunistic routing decisions for interest-annotated messages. Second, the ChitChat system is hybridized [70] to consider both social context and geographic information for learning the social semantics of locations so as to identify worthwhile routing opportunities to destinations and areas of interest. Network density analyses of five real-world datasets is conducted to identify sparse datasets on which to conduct simulations, finding that commonly-used datasets in past DTN research are notably dense and well connected, and suggests two rarely used datasets are appropriate for research into sparse DTNs. Finally, the Catora system is proposed to address congestive-driven degradation of service in DTNs by accomplishing two simultaneous tasks: (i) expedite the delivery of higher quality messages by uniquely ordering messages for transfer and delivery, and (ii) avoid congestion through strategic buffer management and message removal. Through dataset-driven simulations, these systems are found to outperform the state-of-the-art, with ChitChat facilitating delivery in sparse DTNs and Catora unencumbered by congestive conditions --Abstract, page iv

車両・無人航空機を活用した災害時情報共有のためのDTNプロトコル

電気通信大学202

Enhanced Interest Aware PeopleRank for Opportunistic Mobile Social Networks

Network infrastructures are being continuously challenged by increased demand, resource-hungry applications, and at times of crisis when people need to work from homes such as the current Covid-19 epidemic situation, where most of the countries applied partial or complete lockdown and most of the people worked from home. Opportunistic Mobile Social Networks (OMSN) prove to be a great candidate to support existing network infrastructures. However, OMSNs have copious challenges comprising frequent disconnections and long delays. we aim to enhance the performance of OMSNs including delivery ratio and delay. We build upon an interest-aware social forwarding algorithm, namely Interest Aware PeopleRank (IPeR). We explored three pillars for our contribution, which encompass (1) inspect more than one hop (multiple hops) based on IPeR (MIPeR), (2) by embracing directional forwarding (Directional-IPeR), and (3) by utilizing a combination of Directional forwarding and multi-hop forwarding (DMIPeR). For Directional-IPeR, different values of the tolerance factor of IPeR, such as 25% and 75%, are explored to inspect variations of Directional-IPeR. Different interest distributions and users’ densities are simulated using the Social-Aware Opportunistic Forwarding Simulator (SAROS). The results show that (1) adding multiple hops to IPeR enhanced the delivery ratio, number of reached interested forwarders, and delay slightly. However, it increased the cost and decreased F-measure hugely. Consequently, there is no significant gain in these algorithms. (2) Directional-IPeR-75 performed generally better than IPeR in delivery ratio, and the number of reached interested forwarders. Besides, when some of the uninterested forwarders did not participate in messages delivery, which is a realistic behavior, the performance is enhanced and performed better generally in all metrics compared to IPeR. (3) Adding multiple hops to directional guided IPeR did not gain any enhancement. (4) Directional-IPeR-75 performs better in high densities in all metrics except delay. Even though, it enhances delay in sparse environments. Consequently, it can be utilized in disastrous areas, in which few people are with low connectivity and spread over a big area. In addition, it can be used in rural areas as well where there is no existing networks

Efficient Multi-Hop Communications for Software-Defined Wireless Networks

PhD thesisSoftware-Defined Networking (SDN) recently emerged to overcome the difficulty of network control by decoupling the control plane from the data plane. In terms of the wireless medium and mobile devices, although new challenges are introduced into SDN research, SDN promises to address many inherited problems in wireless communication networks. However, centralised SDN control brings concerns of scalability, reliability, and robustness especially for wireless networks. Considering these concerns, the use of physically distributed SDN controllers has been recognized as an effective solution. Nevertheless, it remains a challenge in regard to how the physically distributed controllers effectively communicate to form a logically centralised network control plane. Dissemination is a type of one-to-many communication service which plays an important role in control information exchange. This research focuses on the strategic packet forwarding for more efficient multi-hop communications in software-defined wireless networks. The research aim is to improve the delivery efficiency by exploiting the delay budget and node mobility. To achieve this objective, existing multi-hop forwarding methods and dissemination schemes in wireless networks are investigated and analysed. In the literature, information from the navigation system of mobile nodes has been utilised to identify candidate relay nodes. However, further studies are required to utilise partially predictable mobility based on more generalised navigational information such as the movement direction. In this research, the feasible exploitation of directional movement in path-unconstrained mobility is investigated for efficient multi-hop communications. Simulation results show that the proposed scheme outperforms the state-of-the-art because directional correlation of node movement is considered to dynamically exploit the delay budget for better selection of the relay node(s).Chinese Scholarship Council (CSC

La dissémination de contenus dans les réseaux véhiculaires

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

Privacy engineering for social networks

In this dissertation, I enumerate several privacy problems in online social networks (OSNs) and describe a system called Footlights that addresses them. Footlights is a platform for distributed social applications that allows users to control the sharing of private information. It is designed to compete with the performance of today's centralised OSNs, but it does not trust centralised infrastructure to enforce security properties. Based on several socio-technical scenarios, I extract concrete technical problems to be solved and show how the existing research literature does not solve them. Addressing these problems fully would fundamentally change users' interactions with OSNs, providing real control over online sharing. I also demonstrate that today's OSNs do not provide this control: both user data and the social graph are vulnerable to practical privacy attacks. Footlights' storage substrate provides private, scalable, sharable storage using untrusted servers. Under realistic assumptions, the direct cost of operating this storage system is less than one US dollar per user-year. It is the foundation for a practical shared filesystem, a perfectly unobservable communications channel and a distributed application platform. The Footlights application platform allows third-party developers to write social applications without direct access to users' private data. Applications run in a confined environment with a private-by-default security model: applications can only access user information with explicit user consent. I demonstrate that practical applications can be written on this platform. The security of Footlights user data is based on public-key cryptography, but users are able to log in to the system without carrying a private key on a hardware token. Instead, users authenticate to a set of authentication agents using a weak secret such as a user-chosen password or randomly-assigned 4-digit number. The protocol is designed to be secure even in the face of malicious authentication agents.This work was supported by the Rothermere Foundation and the Natural Sciences and Engineering Research Council of Canada (NSERC)