Algorithms to Find Two-Hop Routing Policies in Multiclass Delay Tolerant Networks

Most of the literature on delay tolerant networks (DTNs) focuses on optimal routing policies exploiting a priori knowledge about nodes mobility traces. For the case in which no a priori knowledge is available (very common in practice), apart from basic epidemic routing, the main approaches focus on controlling two-hop routing policies. However, these latter results commonly employ fluid approximation techniques, which, in principle, do not provide any theoretical bound over the approximation ratio. In our work, we focus on the case without a priori mobility knowledge and we provide approximation algorithms with theoretical guarantees that can be applied to cases where the number of hops allowed in the routing process is arbitrary. Our approach is rather flexible allowing us to address heterogeneous mobility patterns and transmission technologies, to consider explicitly the signaling and transmission costs, and to include also nodes discarding packets after a local timeout. We then provide a comprehensive performance evaluation of our algorithms, showing that two-hop routing provides the best tradeoff between delay and energy and that, in this case, they find solutions very close to the optimal ones with a low overhead. Finally, we compare our methods against some state-of-the-art approaches by means of a DTN simulation environment in realistic settings

Routage et codage réseau inter-session dans les réseaux sociaux mobiles tolérant le délai

We consider Delay Tolerant Mobile Social Networks (DTMSN), made of wireless nodes with intermittent connections and clustered into social communities. This thesis deals with the analysis and design of information transfer strategies in DTMSN. It is mostly dedicated to investigate the use of Inter-Session Network Coding (ISNC) towards this goal. Network coding is a generalization of routing and ISNC is known as a difficult optimization problem in general, specifically because it can easily get detrimental, compared to no coding, if not designed carefully. The first part of this thesis addresses theoretically the optimization problem of the (non-ISNC) routing policy in DTMSNs. We generalize the existing results for homogeneous topologies. The second part of the thesis designs and models a parameterized pairwise ISNC control policy that encompasses both routing and coding controls with an energy constraint. In order to tackle heuristically the optimization problem, the third chapter presents an experimental study of pairwise ISNC to investigate when it can be beneficial or detrimental. We examine the impact on ISNC performance of a number of parameters, such as the constraint on the maximum number of copies per packet, the network load, the buffer size of the relay nodes and the buffer management policies. The fourth chapter addresses the design of decentralized coding criteria allowing to trigger online session mixing if ISNC may be beneficial. We test these coding criteria on both toy topologies and real-world traces, pointing out and explaining the limits of our approach.Nous considérons les Réseaux Sociaux Mobiles Tolérant le Délai (DTMSN), constitués de nœuds sans-fil avec une connectivité intermittente, et groupés en communautés sociales. Cette thèse traite de l’analyse et de la conception de stratégies de transfert de l’information dans les DTMSN. Elle est principalement dédiée à l’étude de codage réseau inter-session (ISNC) dans ce but. Le codage réseau est une généralisation du routage et ISNC est connu comme un problème d’optimisation difficile en général, spécifiquement parce qu’il peut vite devenir nuisible si non conçu avec soin. Le premier chapitre répond théoriquement au problème d’optimisation du routage (sans ISNC) dans les DTMSN. Nous généralisons les résultants existants pour les topologies homogènes. Le deuxième chapitre conçoit et modélise un contrôle de ISNC par paire, qui englobe conjointement le contrôle du routage et du codage, avec une contrainte d’énergie. Pour s’attaquer de façon heuristique à l’optimisation de ce contrôle, le troisième chapitre présente une étude expérimentale visant à identifier quand ISNC est bénéfique ou nuisible, en fonction du nombre maximum de copies par paquet, de la charge du réseau, de la taille de buffer des nœuds relais et de la gestion de buffer. Le quatrième chapitre présente la conception de critères décentralisés de codage, pour déclencher en ligne le mélange de sessions si ISNC peut être bénéfique. Nous testons ces critères sur des topologies simples et sur des traces réelles, en expliquant les limites de notre approche

Forever Young: Aging Control For Smartphones In Hybrid Networks

The demand for Internet services that require frequent updates through small messages, such as microblogging, has tremendously grown in the past few years. Although the use of such applications by domestic users is usually free, their access from mobile devices is subject to fees and consumes energy from limited batteries. If a user activates his mobile device and is in range of a service provider, a content update is received at the expense of monetary and energy costs. Thus, users face a tradeoff between such costs and their messages aging. The goal of this paper is to show how to cope with such a tradeoff, by devising \emph{aging control policies}. An aging control policy consists of deciding, based on the current utility of the last message received, whether to activate the mobile device, and if so, which technology to use (WiFi or 3G). We present a model that yields the optimal aging control policy. Our model is based on a Markov Decision Process in which states correspond to message ages. Using our model, we show the existence of an optimal strategy in the class of threshold strategies, wherein users activate their mobile devices if the age of their messages surpasses a given threshold and remain inactive otherwise. We then consider strategic content providers (publishers) that offer \emph{bonus packages} to users, so as to incent them to download updates of advertisement campaigns. We provide simple algorithms for publishers to determine optimal bonus levels, leveraging the fact that users adopt their optimal aging control strategies. The accuracy of our model is validated against traces from the UMass DieselNet bus network.Comment: See also http://www-net.cs.umass.edu/~sadoc/agecontrol

Socio-economic aware data forwarding in mobile sensing networks and systems

The vision for smart sustainable cities is one whereby urban sensing is core to optimising city operation which in turn improves citizen contentment. Wireless Sensor Networks are envisioned to become pervasive form of data collection and analysis for smart cities but deployment of millions of inter-connected sensors in a city can be cost-prohibitive. Given the ubiquity and ever-increasing capabilities of sensor-rich mobile devices, Wireless Sensor Networks with Mobile Phones (WSN-MP) provide a highly flexible and ready-made wireless infrastructure for future smart cities. In a WSN-MP, mobile phones not only generate the sensing data but also relay the data using cellular communication or short range opportunistic communication. The largest challenge here is the efficient transmission of potentially huge volumes of sensor data over sometimes meagre or faulty communications networks in a cost-effective way. This thesis investigates distributed data forwarding schemes in three types of WSN-MP: WSN with mobile sinks (WSN-MS), WSN with mobile relays (WSN-HR) and Mobile Phone Sensing Systems (MPSS). For these dynamic WSN-MP, realistic models are established and distributed algorithms are developed for efficient network performance including data routing and forwarding, sensing rate control and and pricing. This thesis also considered realistic urban sensing issues such as economic incentivisation and demonstrates how social network and mobility awareness improves data transmission. Through simulations and real testbed experiments, it is shown that proposed algorithms perform better than state-of-the-art schemes.Open Acces

Device-Centric Cooperation in Mobile Networks

The increasing popularity of applications such as video streaming in today's mobile devices introduces higher demand for throughput, and puts a strain especially on cellular links. Cooperation among mobile devices by exploiting both cellular and local area connections is a promising approach to meet the increasing demand. In this paper, we consider that a group of cooperative mobile devices, exploiting both cellular and local area links and within proximity of each other, are interested in the same video content. Traditional network control algorithms introduce high overhead and delay in this setup as the network control and cooperation decisions are made in a source-centric manner. Instead, we develop a device-centric stochastic cooperation scheme. Our device-centric scheme; DcC allows mobile devices to make control decisions such as flow control, scheduling, and cooperation without loss of optimality. Thanks to being device-centric, DcC reduces; (i) overhead; i.e., the number of control packets that should be transmitted over cellular links, so cellular links are used more efficiently, and (ii) the amount of delay that each packet experiences, which improves quality of service. The simulation results demonstrate the benefits of DcC

Towards Realistic Performance Evaluation of Delay Tolerant Network

Abstract: -Delay Tolerant Network (DTN) is a type of wireless ad hoc network in which route is established between a pair of nodes in spite of having long delays and frequent route ruptures. To ensure successful communication in such an environment a robust routing protocol is used the performance of which depends upon various factors such as transmission range, processing capability, transmission delays, bandwidth and the environment. Many researchers have evaluated the performance of routing protocol in an idealistic environment and only few have made an effort to evaluate its performance for realistic environment. This paper is an effort to evaluate the efficacy of DTN in realistic as well as idealistic conditions by designing a simulator in MATLAB-7.0. To make the scenario realistic, obstacles of different shapes, types and numbers were introduced in the simulation region. The results show that the performance of routing protocol vary significantly by changing the environment i.e. the results for idealistic scenario cannot be applied for realistic scenario

Adaptive Optimal Stochastic Control of Delay--Tolerant Networks

International audienceOptimal stochastic control of delay tolerant networks is studied in this paper. First, the structure of optimal two-hop forwarding policies is derived. In order to be implemented, such policies require knowledge of certain global system parameters such as the number of mobiles or the rate of contacts between mobiles. But, such parameters could be unknown at system design time or may even change over time. In order to address this problem, adaptive policies are designed that combine estimation and control: based on stochastic approximation techniques, such policies are proved to achieve optimal performance in spite of lack of global information. Furthermore, the paper studies interactions that may occur in the presence of several DTNs which compete for the access to a gateway node. The latter problem is formulated as a cost-coupled stochastic game and a unique Nash equilibrium is found. Such equilibrium corresponds to the system configuration in which each DTN adopts the optimal forwarding policy determined for the single network problem

Optimal Control of Epidemics in the Presence of Heterogeneity

We seek to identify and address how different types of heterogeneity affect the optimal control of epidemic processes in social, biological, and computer networks. Epidemic processes encompass a variety of models of propagation that are based on contact between agents. Assumptions of homogeneity of communication rates, resources, and epidemics themselves in prior literature gloss over the heterogeneities inherent to such networks and lead to the design of sub-optimal control policies. However, the added complexity that comes with a more nuanced view of such networks complicates the generalizing of most prior work and necessitates the use of new analytical methods. We first create a taxonomy of heterogeneity in the spread of epidemics. We then model the evolution of heterogeneous epidemics in the realms of biology and sociology, as well as those arising from practice in the fields of communication networks (e.g., DTN message routing) and security (e.g., malware spread and patching). In each case, we obtain computational frameworks using Pontryagin’s Maximum Principle that will lead to the derivation of dynamic controls that optimize general, context-specific objectives. We then prove structures for each of these vectors of optimal controls that can simplify the derivation, storage, and implementation of optimal policies. Finally, using simulations and real-world traces, we examine the benefits achieved by including heterogeneity in the control decision, as well as the sensitivity of the models and the controls to model parameters in each case