The Experts below are selected from a list of 9327 Experts worldwide ranked by ideXlab platform
Cristina Cervello-pastor - One of the best experts on this subject based on the ideXlab platform.
-
From Delay-Tolerant Networks to Vehicular Delay-Tolerant Networks
IEEE Communications Surveys & Tutorials, 2012Co-Authors: Paulo Rogério Pereira, Augusto Casaca, Vasco N G J Soares, Joel J P C Rodrigues, Joan Triay, Cristina Cervello-pastorAbstract:This paper provides an introductory overview of Vehicular Delay-Tolerant Networks. First, an introduction to Delay-Tolerant Networks and Vehicular Delay-Tolerant Networks is given. Delay-Tolerant schemes and protocols can help in situations where network connectivity is sparse or with large variations in density, or even when there is no end-to-end connectivity by providing a communications solution for non real-time applications. Some special issues like routing are addressed in the paper and an introductory description of applications and the most important projects is given. Finally, some research challenges are discussed and conclusions are detailed.
Paulo Rogério Pereira - One of the best experts on this subject based on the ideXlab platform.
-
WiMob - Multicast routing protocol for Vehicular Delay-Tolerant Networks
2012 IEEE 8th International Conference on Wireless and Mobile Computing Networking and Communications (WiMob), 2012Co-Authors: Adriano Palma, Paulo Rogério Pereira, Augusto CasacaAbstract:Disruptions, high dynamism and no end-to-end communication are some of the Vehicular Delay-Tolerant Networks (VDTNs) main characteristics. This paper describes the implementation of a new VDTN multicast routing protocol which makes use of knowledge about previous encounters to estimate congestion and density and better spread data bundles and limit the number of copies to reduce overhead. After a brief introduction to Delay-Tolerant Networks, VDTNs, and protocols, the new multicast routing protocol, named NewVDTN, is described. It will be compared against Epidemic Multicast. The protocols were implemented and tested on The Opportunistic Network Environment simulator, concluding that NewVDTN shows a similar or better delivery ratio and Delay with an enormous reduction of overhead, as compared with Epidemic Multicast.
-
From Delay-Tolerant Networks to Vehicular Delay-Tolerant Networks
IEEE Communications Surveys & Tutorials, 2012Co-Authors: Paulo Rogério Pereira, Augusto Casaca, Vasco N G J Soares, Joel J P C Rodrigues, Joan Triay, Cristina Cervello-pastorAbstract:This paper provides an introductory overview of Vehicular Delay-Tolerant Networks. First, an introduction to Delay-Tolerant Networks and Vehicular Delay-Tolerant Networks is given. Delay-Tolerant schemes and protocols can help in situations where network connectivity is sparse or with large variations in density, or even when there is no end-to-end connectivity by providing a communications solution for non real-time applications. Some special issues like routing are addressed in the paper and an introductory description of applications and the most important projects is given. Finally, some research challenges are discussed and conclusions are detailed.
Eitan Altman - One of the best experts on this subject based on the ideXlab platform.
-
Adaptive Optimal Stochastic Control of Delay--Tolerant Networks
IEEE Transactions on Mobile Computing, 2016Co-Authors: Eitan Altman, Francesco De Pellegrini, Daniele Miorandi, Giovanni NegliaAbstract:Optimal 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.
-
A new proposal for reliable unicast and multicast transport in Delay Tolerant Networks
2011Co-Authors: Arshad Ali, Eitan Altman, Tijani Chahed, Manoj Kumar Panda, Lucile SassatelliAbstract:We propose a new scheme for reliable transport, both for unicast and multicast flows, in Delay Tolerant Networks (DTNs). Reliability is ensured through the use of Global Selective ACKnowledgements (G-SACKs) which contain detailed (and potentially global) information about the receipt of packets at all the destinations. The motivation for using G-SACKs comes from the observation that one should take the maximum advantage of the contact opportunities which occur quite infrequently in DTNs. We also propose sharing of "packet header space" with G-SACK information and allow for random linear coding at the relay nodes. Our results from extensive simulations of the proposed scheme quantify the gains due to each new feature.
-
Risk sensitive optimal control framework applied to Delay Tolerant Networks
2011Co-Authors: Eitan Altman, Francesco De Pellegrini, Veeraruna Kavitha, Vijay Kamble, Vivek BorkarAbstract:—Epidemics dynamics can describe the dissemination of information in Delay Tolerant Networks, in peer to peer Networks and in content delivery Networks. The control of such dynamics has thus gained a central role in all of these areas. However, a major difficulty in this context is that the objective functions to be optimized are often not additive in time but are rather multiplicative. The classical objective function in DTNs, i.e., the successful delivery probability of a message within a given deadline, falls precisely in this category, because it takes often the form of the expectation of the exponent of some integral cost. So far, models involving such costs have been solved by interchanging the order of expectation and the exponential function. While reducing the problem to a standard optimal control problem, this interchange is only tight in the mean field limit obtained as the population tends to infinity. In this paper we identify a general framework from optimal control in finance, known as risk sensitive control, which let us handle the original (multiplicative) cost and obtain solutions to several novel control problems in DTNs. In particular, we can derive the structure of state-dependent controls that optimize transmission power at the source node. Further, we can account for the propagation loss factor of the wireless medium while obtaining these controls, and, finally, we address power control at the destination node, resulting in a novel threshold optimal activation policy. Combined optimal power control at source and destination nodes is also obtained. Index Terms—Delay Tolerant Networks, Markov Decision Process, Risk Sensitive Control I. INTRODUCTION Delay Tolerant Networks (DTNs) gained the interest of the research community in recent past [2], [3]. They have been identified as a promising mean to transport data in intermittently connected Networks. DTNs in particular, sustain communications in a networked system where no continuous connectivity guarantee can be assumed [4], [5]. Messages are carried from source to destination via relay nodes adopting store and carry type forwarding protocols; such protocols basically rely on the underlying node mobility pattern. The core problem in DTNs is to efficiently route messages towards the intended destination. We observe that traditional techniques for routing perform very poorly in this context due to frequent disruptions, and furthermore mobile nodes rarely possess information on the upcoming encounters they are going to experience [6], [7]. An intuitive and rather robust solution is to disseminate multiple copies of the message in the network. This is meant to ensure that at least some of them will reach the destination node within some deadline [5], [8].
-
optimal activation and transmission control in Delay Tolerant Networks
International Conference on Computer Communications, 2010Co-Authors: Eitan Altman, Amar Prakash Azad, Tamer Baoar, Francesco De PellegriniAbstract:Much research has been devoted to maximize the life time of mobile ad-hoc Networks. Life time has often been defined as the time elapsed until the first node is out of battery power. In the context of static Networks, this could lead to disconnectivity. In contrast, Delay Tolerant Networks (DTNs) leverage the mobility of relay nodes to compensate for lack of permanent connectivity, and thus enable communication even after some nodes deplete their stored energy. One can thus consider the lifetimes of nodes as some additional parameters that can be controlled to optimize the performance of a DTN. In this paper, we consider two ways in which the energy state of a mobile can be controlled. Both listening and transmission require energy, besides each of these has a different type of effect on the network performance. Therefore we consider a joint optimization problem consisting of: i) activation, which determines when a mobile will turn on in order to receive packets, and ii) transmission control, which regulates the beaconing. The optimal solutions are shown to be of the threshold type. The findings are validated through extensive simulations.
-
dynamic control of coding in Delay Tolerant Networks
arXiv: Networking and Internet Architecture, 2009Co-Authors: Eitan Altman, Francesco De Pellegrini, Lucile SassatelliAbstract:Delay Tolerant Networks (DTNs) leverage the mobility of relay nodes to compensate for lack of permanent connectivity and thus enable communication between nodes that are out of range of each other. To decrease message delivery Delay, the information to be transmitted is replicated in the network. We study replication mechanisms that include Reed-Solomon type codes as well as network coding in order to improve the probability of successful delivery within a given time limit. We propose an analytical approach that allows us to compute the probability of successful delivery. We study the effect of coding on the performance of the network while optimizing parameters that govern routing.
Guohong Cao - One of the best experts on this subject based on the ideXlab platform.
-
a routing protocol for socially selfish Delay Tolerant Networks
Ad Hoc Networks, 2012Co-Authors: Wei Gao, Sencun Zhu, Guohong CaoAbstract:Existing routing algorithms for Delay Tolerant Networks (DTNs) assume that nodes are willing to forward packets for others. In the real world, however, most people are socially selfish; i.e., they are willing to forward packets for nodes with whom they have social ties but not others, and such willingness varies with the strength of the social tie. Following the philosophy of design for user, we propose a Social Selfishness Aware Routing (SSAR) algorithm to cope with user selfishness and provide good routing performance in an efficient way. To select an effective forwarding node, SSAR considers both users' willingness to forward and their contact opportunity, and derives a metric with mathematical modeling and machine learning techniques to measure the forwarding capability of the mobile nodes. Moreover, SSAR formulates the data forwarding process as a Multiple Knapsack Problem with Assignment Restrictions (MKPAR) to satisfy user demands for selfishness and performance. Trace-driven simulations show that SSAR allows users to maintain selfishness and achieves good routing performance with low transmission cost.
-
routing in socially selfish Delay Tolerant Networks
International Conference on Computer Communications, 2010Co-Authors: Sencun Zhu, Guohong CaoAbstract:Existing routing algorithms for Delay Tolerant Networks(DTNs) assume that nodes are willing to forward packets for others. In the real world, however, most people are socially selfish; i.e., they are willing to forward packets for nodes with whom they have social ties but not others, and such willingness varies with the strength of the social tie. Following the philosophy of design for user, we propose a Social Selfishness Aware Routing (SSAR) algorithm to allow user selfishness and provide better routing performance in an efficient way. To select a forwarding node, SSAR considers both users' willingness to forward and their contact opportunity, resulting in a better forwarding strategy than purely contact-based approaches. Moreover, SSAR formulates the data forwarding process as a Multiple Knapsack Problem with Assignment Restrictions (MKPAR) to satisfy user demands for selfishness and performance. Trace-driven simulations show that SSAR allows users to maintain selfishness and achieves better routing performance with low transmission cost.
-
multicasting in Delay Tolerant Networks a social network perspective
Mobile Ad Hoc Networking and Computing, 2009Co-Authors: Wei Gao, Bo Zhao, Guohong CaoAbstract:Node mobility and end-to-end disconnections in Delay Tolerant Networks (DTNs) greatly impair the effectiveness of data dissemination. Although social-based approaches can be used to address the problem, most existing solutions only focus on forwarding data to a single destination. In this paper, we are the first to study multicast in DTNs from the social network perspective. We study multicast in DTNs with single and multiple data items, investigate the essential difference between multicast and unicast in DTNs, and formulate relay selections for multicast as a unified knapsack problem by exploiting node centrality and social community structures. Extensive trace-driven simulations show that our approach has similar delivery ratio and Delay to the Epidemic routing, but can significantly reduce the data forwarding cost measured by the number of relays used.
Augusto Casaca - One of the best experts on this subject based on the ideXlab platform.
-
WiMob - Multicast routing protocol for Vehicular Delay-Tolerant Networks
2012 IEEE 8th International Conference on Wireless and Mobile Computing Networking and Communications (WiMob), 2012Co-Authors: Adriano Palma, Paulo Rogério Pereira, Augusto CasacaAbstract:Disruptions, high dynamism and no end-to-end communication are some of the Vehicular Delay-Tolerant Networks (VDTNs) main characteristics. This paper describes the implementation of a new VDTN multicast routing protocol which makes use of knowledge about previous encounters to estimate congestion and density and better spread data bundles and limit the number of copies to reduce overhead. After a brief introduction to Delay-Tolerant Networks, VDTNs, and protocols, the new multicast routing protocol, named NewVDTN, is described. It will be compared against Epidemic Multicast. The protocols were implemented and tested on The Opportunistic Network Environment simulator, concluding that NewVDTN shows a similar or better delivery ratio and Delay with an enormous reduction of overhead, as compared with Epidemic Multicast.
-
From Delay-Tolerant Networks to Vehicular Delay-Tolerant Networks
IEEE Communications Surveys & Tutorials, 2012Co-Authors: Paulo Rogério Pereira, Augusto Casaca, Vasco N G J Soares, Joel J P C Rodrigues, Joan Triay, Cristina Cervello-pastorAbstract:This paper provides an introductory overview of Vehicular Delay-Tolerant Networks. First, an introduction to Delay-Tolerant Networks and Vehicular Delay-Tolerant Networks is given. Delay-Tolerant schemes and protocols can help in situations where network connectivity is sparse or with large variations in density, or even when there is no end-to-end connectivity by providing a communications solution for non real-time applications. Some special issues like routing are addressed in the paper and an introductory description of applications and the most important projects is given. Finally, some research challenges are discussed and conclusions are detailed.