IEEE 802.11 PHY supports multiple transmission rates according to multiple different modulations and coding schemes. Each WiFi station selects its own transmission rate according to its own algorithm; in particular, the IEEE 802.11 standards do not specify the bit-rate selection method. Although many adaptive bit-rate selection algorithms have been proposed, there is limited research and evaluation on the performance of such algorithms for roadside networks, especially in cases with multi-vehicle roadside multi-vehicular WiFi networks. In this thesis we propose an opportunistic highest bit-rate algorithm, Opportunistic Highest Bit-Rate Multi-Vehicular WiFi Networks (OHBR-MVN), specifically for roadside multi-vehicular WiFi networks. Our proposal is based on three key characteristics of such networks: (1) vehicles will drive closer to, and eventually pass, the roadside WiFi station, experiencing a progressively better transmission environment; (2) the vast majority of data transmitted in single-vehicle drive-by downloading scenarios occurs at the maximum transmission rate; (3) vehicles that transmit at less than the maximum rate do so at the expense of those that could send more data at a higher transmission rate. We therefore believe that transmitting only at the highest possible bit-rate is the preferred algorithm for such networks. Further, this approach keeps the bit-rate selection extremely simple, avoiding the complexity and resulting problems of adaptive approaches. Through a series of experiments that compare the throughput of both fixed and adaptive bit-rate selection algorithms we show that our approach yields both higher throughput and better fairness characteristics, while being significantly simple, and thus more robust.

The delay tolerant networks (DTNs) is characterized by frequent disconnections and long delays of links among devices due to mobility, sparse deployment of devices, attacks, and noise, etc. Considerable research efforts have been devoted recently to DTNs enabling communications between network entities with intermittent connectivity. Unfortunately, mobile devices have limited energy capacity, and the fundamental problem is that traditional power-saving mechanisms are designed assuming well connected networks. Due to much larger inter-contact durations than contact durations, devices spend most of their life time in the neighbor discovery, and centralized power-saving strategies are difficult. Consequently, mobile devices consume a significant amount of energy in the neighbor discovery, rather than in infrequent data transfers. Therefore, distributed energy efficient neighbor discovery protocols for DTNs are essential to minimize the degradation of network connectivity and maximize the benefits from mobility. In this thesis, we develop sleep scheduling protocols in the medium access control (MAC) layer that are adaptive and distributed under different clock synchronization conditions: synchronous, asynchronous, and semi-asynchronous. In addition, we propose a distributed clock synchronization protocol to mitigate the clock synchronization problem in DTNs. Our research accomplishments are briefly outlined as follows: Firstly, we design an adaptive exponential beacon (AEB) protocol. By exploiting the trend of contact availability, beacon periods are independently adjusted by each device and optimized using the distribution of contact durations. The AEB protocol significantly reduces energy consumption while maintaining comparable packet delivery delay and delivery ratio. Secondly, we design two asynchronous clock based sleep scheduling (ACDS) protocols. Based on the fact that global clock synchronization is difficult to achieve in general, predetermined patterns of sleep schedules are constructed using hierarchical arrangements of cyclic difference sets such that devices independently selecting different duty cycle lengths are still guaranteed to have overlapping awake intervals with other devices within the communication range. Thirdly, we design a distributed semi-asynchronous sleep scheduling (DSA) protocol. Although the synchronization error is unavoidable, some level of clock accuracy may be possible for many practical scenarios. The sleep schedules are constructed to guarantee contacts among devices having loosely synchronized clocks, and parameters are optimized using the distribution of synchronization error. We also define conditions for which the proposed semi-asynchronous protocol outperforms existing asynchronous sleep scheduling protocols. Lastly, we design a distributed clock synchronization (DCS) protocol. The proposed protocol considers asynchronous and long delayed connections when exchanging relative clock information among nodes. As a result, smaller synchronization error achieved by the proposed protocol allows more accurate timing information and renders neighbor discovery more energy efficient. The designed protocols improve the lifetime of mobile devices in DTNs by means of energy efficient neighbor discoveries that reduce the energy waste caused by idle listening problems.

Billions of people in the world live under heavy information censorship. We propose a new class of delay tolerant network (DTN), known as a censorship tolerant network (CTN), to counter the growing practice of Internet-based censorship. CTNs should provide strict guarantees on the privacy of both information shared within the network and the identities of network participants. CTN software needs to be publicly available as open source software and run on personal mobile devices with real-world computational, storage, and energy constraints. We show that these simple assumptions and system constraints have a non-obvious impact on the design and implementation of CTNs, and serve to differentiate our system design from previous work. We design data routing within a CTN using a new paradigm: one where nodes operate selfishly to maximize their own utility, make decisions based only on their own observations, and only communicate with nodes they trust. We introduce the Laissez-faire framework, an incentivized approach to CTN routing. Laissez-faire does not mandate any specific routing protocol, but requires that each node implement tit-for-tat by keeping track of the data exchanged with other trusted nodes. We propose several strategies for valuing and retrieving content within a CTN. We build a prototype BlackBerry implementation and conduct both controlled lab and field trials, and show how each strategy adapts to different network conditions. We further demonstrate that, unlike existing approaches to routing, Laissez-faire prevents free-riding. We build an efficient and reliable data transport protocol on top of the Short Message Service (SMS) to serve a control channel for the CTN. We conduct a series of experiments to characterise SMS behaviour under bursty, unconventional workloads. This study examines how variables such as the transmission order, delay between transmissions, the network interface used, and the time-of-day affect the service. We present the design and implementation of our transport protocol. We show that by adapting to the unique channel conditions of SMS we can reduce message overheads by as much as 50\% and increase data throughput by as much as 545% over the approach used by existing applications. A CTN's dependency on opportunistic communication imposes a significant burden on smartphone energy resources. We conduct a large-scale user study to measure the energy consumption characteristics of 20100 smartphone users. Our dataset is two orders of magnitude larger than any previous work. We use this dataset to build the Energy Emulation Toolkit (EET) that allows developers to evaluate the energy consumption requirements of their applications against real users' energy traces. The EET computes the successful execution rate of energy-intensive applications across all users, specific devices, and specific smartphone user-types. We also consider active adaptation to energy constraints. By classifying smartphone users based on their charging characteristics we demonstrate that energy level can be predicted within 72% accuracy a full day in advance, and through an Energy Management Oracle energy intensive applications, such as CTNs, can adapt their execution to maintain the operation of the host device.

L'internet des Objets (IoT) est habituellement présenté comme l'ensemble d'objets interconnectés à travers un réseau qui est, en pratique, Internet. Or, il existe beaucoup de cas où la connectivité est intermittente à cause des interfaces radio courte-portées et des contraintes d'économie d'énergie. L'architecture de réseautage tolérant les délais (DTN) ainsi que le Bundle Protocole (BP) sont considérés comme des solutions viables pour résoudre ce genre de challenges grâce au mécanisme store-carry-and-forward. Cette thèse vise à fournir des supports de programmation adaptés autant à l'IoT qu'au contexte DTN. Dans ce but, les challenges relevant du DTN et de l'IoT (DT-IoT) sont étudiés et quelques principes de design logiciels sont proposés. Ces principes ont pour but d'optimiser la réactivité et l'efficacité des applications ayant pour cible un contexte DT- IoT. La première contribution est la définition d'un support de programmation orienté ressources, nommé BoaP. Ce support fournit un protocole de requête/réponse grâce à une transposition de CoAP (Contrained Application Protocol). Cette transposition est composée d'ajustements fondamentaux et d'améliorations pour utiliser BP en tant que couche de transport. BoaP a été implémenté et testée dans un petit réseau physique. Une méthode pour évaluer des intergiciels dans des réseaux DTNs est présentée. Un outil implémentant cette méthode a été développé. Il repose sur une plateforme de virtualisation qui simule les contacts réseaux tout en émulant les nœuds du réseau. Cet outil a été utilisé pour exécuter des expériences pour évaluer la validité de BoaP. Enfin, un autre support de programmation est examiné. Celui-ci adopte une approche orientée service et respecte les contraintes REST (Representational State Transfer). Il se repose sur BoaP a été créé avec l'IoT en tête et est adapté à l’environnement DTN. La découverte exploite une interface de publications/souscriptions. Les descripteurs de services contiennent des champs spécifiques pour informer de la disponibilité de leur fournisseurs. / The Internet of Things (IoT) is usually presented as a set of THINGS interconnected through a network that is, in practice, Internet. However, there exist many contexts in which the connectivity is intermittent due to short-range wireless communication means or energy constraints. The Delay Tolerant Networking (DTN) architecture and the Bundle Protocol (BP) are known to overcome this communication challenge as they provide communication means by relying on a store-carry-and- forward mechanism. This thesis aims to provide programming supports adapted to both IoT and DTN contexts. For this, both DTN and IoT (DT-IoT) challenges are studied and several design principles are proposed. These principles aim to optimize reactivity and efficiency of applications targeting the DT-IoT context. The first contribution is the definition of a resource-oriented programming support, named BoaP, to enable a DT-IoT. It provides a protocol based on request/response thanks to a transposition of CoAP (Contrained Application Protocol). This transposition consists of fundamental adjustments and enhancements to use BP as the underlying transport protocol. BoaP has been implemented and tested in a small physical network. A method to evaluate middleware systems in DTNs is presented. A tool implementing this method has been developed. It relies on a virtualization platform that simulates network contacts and emulates network devices. This tool was used to run experimentations that assessed the validity of BoaP. Finally, another programming support is investigated. It follows a service-oriented approach and respects REST (Representational State Transfer) constraints. It is built on top of BoaP with IoT in mind and is adapted to DTN environments. Its discovery/advertisement exploits a publish/subscribe interface. Service descriptors contain specific fields to inform on the availability of the service providers. %Finally, requests are extended with some options to enforce conditions on geographic or time context.

Les réseaux tolérants aux délais sont aujourd’hui une alternative prometteuse aux réseaux traditionnels basés sur une infrastructure, encore peu déployée. Il existe plusieurs manières d’évaluer les performances d’un tel réseau : expériences de déploiement grandeur nature, modèles théoriques, simulation, émulation, jeu de traces. Chacune a ses avantages et inconvénients, tant en termes de coûts matériels, de réalisme, de temps nécessaire ou de capacité à gérer des noeuds réels. Cependant, aucune ne répond réellement aux besoins des développeurs d’applications. Dans cette thèse, nous nous focaliserons sur l’émulation. Dans une première partie, nous nous intéresserons aux entrées possibles pour un tel système. Nous proposons tout d’abord un modèle analytique pour prévoir le taux de pertes dans un réseau où les noeuds possèdent une mémoire limitée à un seul paquet. Ensuite, inspirés par les approches de mise à l’échelle de traces de la littérature, nous étudions les hypothèses prises pour l’analyse statistique de traces réelles, et montrons leur influence sur les lois de probabilité obtenues ainsi que les performances réseau observées. Nous étendons ensuite cette étude à la totalité du cycle de vie des traces réelles, en considérant la collecte de données, le filtrage et la mise à l’échelle de celles-ci. Dans une seconde partie, nous proposons une architecture possible d’un émulateur DTN hybride, c’est-à-dire comportant à la fois des noeuds réels sous forme d’intelliphones, et des noeuds virtuels. Le principal avantage ici est de pouvoir évaluer des applications réelles, éventuellement déjà existantes, dans un contexte DTN, et ce de manière aussi transparente que possible. Nous identifions les limites des approches existantes, ce qui nous permet d’établir une liste de spécifications pour notre système. Nous proposons ensuite un système, nommé HINT, permettant de remplir ces spécifications. L’ensemble est ensuite validé, puis appliqué à l’étude de quelques exemples. / Delay Tolerant Networks are currently a promising alternative to infrastructure-based networks, but they have not seen a wide deployment so far. There are several ways to evaluate the performance of such networks: field trials, theoretical models, simulation, emulation or replaying contact datasets. Each one has its advantages and drawbacks in terms of material cost, realism, required time or ability to manage real nodes. However, none of them effectively addresses the needs of application developers. In this thesis, we will focus on emulation. In a first part, we will deal with possible inputs for such a system. We first propose an analytical model to predict the drop ratio in a network where nodes have a one-packet buffer. Then, taking inspiration from trace scaling approaches from the literature, we study the hypotheses and assumptions taken for real traces statistical analyses, showing their impact on the obtained probability distributions and observed network performance metrics. We then extend this study to the whole life cycle of real traces, by considering data collection, filtering and scaling. In a second part, we propose a possible architecture for a hybrid DTN emulator, using both real nodes as smartphones and virtual nodes. The main advantage here is to be able to evaluate real applications, including preexisting ones, in a DTN context, doing so as transparently as possible. We identify the limitations of existing approaches, which helps us build a list of specifications for our system. Then, we propose a system called HINT which matches these specifications. HINT is validated, and applied to the study of some examples.

Small mobile devices with networking capabilities are becoming more and more readily available and used. These devices can be used to form mobile ad hoc networks to communicate, where no infrastructure for network communication exist or where it has been destroyed or is overloaded e.g. in a natural disaster such as a hurricane. Such networks are almost never fully connected, and are part of the category of delay/disruption-tolerant networks (DTN) and suffer from limited resources e.g. bandwidth, storage and limited energy supply. The Opportunistic DTN Routing With Window-aware Adaptive Replication (ORWAR) is a delaytolerant protocol intended to be used in disaster relief efforts or emergency operations were a DTN could be a fast way to establish communication. In these kinds of scenarios high success rate together with efficient usage of the networks resources are critical to the success of such operations. ORWAR has been implemented and simulated on a high-level simulator, with promising results. To make a better assessment about what ORWARs performance would be in a real world network, more realistic and detailed simulations are needed. This Master's Thesis describes the design, implementation and evaluation of ORWAR in the network simulator ns-3, which simulates networks down to physical layer. The contributions of this thesis is a extension to ns-3 giving it an framework with support for the bundle protocol and delay-tolerant routing protocols and an evaluation of the ORWAR performance using more detailed simulations. The simulations represent a city scenario in down-town Helsinki city, Finland, were pedestrians, cars and trams form a network to communicate. The simulations with a higher level of detail has added to insight about the protocol. The obtained results showed that the high-level simulation may be overly optimistic and hides implementation details. On the other hand, some assumptions were found to be too pessimistic. For example we have shown that ORWAR actually performs better than the high level simulations, with regard to partial transmissions and that the high-level simulations have rather optimistic assumptions regarding the latency.

The Aim of this thesis is to implement the "Opportunistic DTN Routing with Window-aware Adaptive Replication" (ORWAR) protocol on the Android platform.Delay-Tolerant Networks (DTNs) are particular mobile ad-hoc network (MANET) architectures that try to solve the issues related to the lack of point to point connectivity between the nodes of the network or between its sub-networks (partitions). The general approach is based on techniques of store-carry-forward of the messages whereby delivery can be achieved even in partitioned networks, though with mobility-dependent delays. DTNs can be considered as a means of communication for scenarios where infrastructure-based networks cannot be deployed or get dysfunctional for some reasons, such as in the case of a natural disaster or highly overloaded infrastructure. ORWAR is a DTN protocol that tries to exploit knowledge about the context of mobile nodes (speed, direction of movement and radio range) to estimate the size of a contact window in order to avoid the energy waste deriving from partial transmissions. This report presents the design and the implementation of the protocol on the Android platform. It then describes some functional tests together with an analysis of the energy consumption and the performance reachable on our test device Android Development Phone 1.

Rapid urbanization burdens city infrastructure and creates the need for local governments to maximize the usage of resources to serve its citizens. Smart city projects aim to alleviate the urbanization problem by deploying a vast amount of Internet-of-things (IoT) devices to monitor and manage environmental conditions and infrastructure. However, smart city projects can be extremely expensive to deploy and manage partly due to the cost of providing Internet connectivity via 5G or WiFi to IoT devices. This thesis proposes the use of delay tolerant networks (DTNs) as a backbone for smart city communication; enabling developing communities to become smart cities at a fraction of the cost. A model is introduced to aid policy makers in designing and evaluating the expected performance of such networks and results are presented based on a public transit network data-set from Chapel Hill, North Carolina and Louisville, Kentucky. We also demonstrate that the performance of our network can be optimized using algorithms associated on set-cover and Influence maximization problems. Several optimization algorithms are then developed to facilitate the effective placement of gateways within the network model and these algorithms are shown to outperform traditional centrality-based algorithms in terms of cost-efficiency and network performance. Finally, other innovative ways of improving network performance in a low-cost smart city is discussed.

Technology has reached a point where it has become feasible to develop unmanned aerial vehicles (UAVs), that is aircraft without a human pilot on board. Given that future UAVs can be autonomous and cheap, applications of swarming UAVs are possible. In this thesis we have studied a reconnaissance application using swarming UAVs and how these UAVs can communicate the reconnaissance data. To guide the UAVs in their reconnaissance mission we have proposed a pheromone based mobility model that in a distributed manner guides the UAVs to areas not recently visited. Each UAV has a local pheromone map that it updates based on its reconnaissance scans. The information in the local map is regularly shared with a UAV’s neighbors. Evaluations have shown that the pheromone logic is very good at guiding the UAVs in their cooperative reconnaissance mission in a distributed manner. Analyzing the connectivity of the UAVs we found that they were heavily partitioned which meant that contemporaneous communication paths generally were not possible to establish. This means that traditional mobile ad hoc network (MANET) routing protocols like AODV, DSR and GPSR will generally fail. By using node mobility and the store-carry-forward principle of delay-tolerant routing the transfer of messages between nodes is still possible. In this thesis we propose location aware routing for delay-tolerant networks (LAROD). LAROD is a beacon-less geographical routing protocol for intermittently connected mobile ad hoc networks. Using static destinations we have shown by a comparative study that LAROD has almost as good delivery rate as an epidemic routing scheme, but at a substantially lower overhead. / <p>Report code: LiU-Tek-Lic-2008:14</p>

People all around the world have their internet access censored or monitored by governments or large corporations. Whistleblowers and human rights activists oftentimes need to communicate in secret to avoid persecution by the powerful organization monitoring their communications. Current anonymity systems often depend on the public internet, and as such are subject to some degree of interference. Cloak is a textual communication network created to hide the existence of the network itself from an outside observer, such as a repressive government or corrupt corporation. Cloak does not use the public internet, and as such would evade the majority of the monitoring in place today. Cloak also does not use any special infrastructure or create its own infrastructure, minimizing the risk of infrastructure attacks. Finally, Cloak provides plausible deniability for its users should they be investigated. Cloak works by hiding its messages inside of normal phone activity. Two Cloak nodes can identify each other by looking at wifi probe messages that are generated by phones in the vicinity of an open wifi hotspot. They can then connect to the hotspot and browse like normal, while hiding messages inside their browsing. Because this is open wifi, the other nodes can see the hidden messages and store them, and carry them closer to their destination. Cloak can hide its messages in a lot of ways. It can first send images with messages embedded in them. It can also use places where a website asks for data in a opaque format, such as YouTube video ids. Finally, if encrypted browsing is available, a Cloak node can just send the encrypted message and act like something went wrong with its encrypted browsing.