1,721,116 research outputs found
An efficient routing protocol for hierarchical ad-hoc mobile networks
No full textWe introduce a new model of ad-hoc mobile networks, which we call hierarchical, that are comprised of dense subnetworks of mobile users (corresponding to highly populated geographical areas, such as cities), interconnected across access ports by sparse but frequently used connections (such as highways). For such networks, we present an efficient routing protocol which extends the idea (introduced in [4]) of exploiting the co-ordinated motion of a small part of an ad-hoc mobile network (the "support") to achieve very fast communication between any two mobile users of the network. The basic idea of the new protocol presented here is, instead of using a unique (large) support for the whole network, to employ a hierarchy of (small) supports (one for each city) and also take advantage of the regular traffic of mobile users across the interconnection highways to communicate between cities. We combine here theoretical analysis (average case estimations based on random walk properties) and experimental implementations (carried out using the LEDA platform) to claim and validate results showing that such a hierarchical routing approach is, for this class of ad-hoc mobile networks, significantly more efficient than a simple extension of the basic "support" idea presented in [4]
Distributed communication algorithms for ad hoc mobile networks
No full textAn ad hoc mobile network is a collection of mobile hosts, with wireless communication capabilities, forming a temporary network without the aid of any established fixed infrastructure. In such networks, topological connectivity is subject to frequent, unpredictable change. Our work focuses on networks with high rate of such changes to connectivity. For such dynamically changing networks we propose protocols which exploit the co-ordinated (by the protocol) motion of a small part of the network. We show that such protocols can be designed to work correctly and efficiently even in the case of arbitrary (but not malicious) movements of the hosts not affected by the protocol. We also propose a methodology for the analysis of the expected behavior of protocols for such networks, based on the assumption that mobile hosts (those whose motion is not guided by the protocol) conduct concurrent random walks in their motion space. In particular, our work examines the fundamental problem of communication and proposes distributed algorithms for it. We provide rigorous proofs of their correctness, and also give performance analyses by combinatorial tools. Finally, we have evaluated these protocols by experimental means. © 2002 Elsevier Science (USA). All rights reserved
A trusted architectural model for interconnecting testbeds of wireless sensor networks
No full textDesigning wireless sensor networks is inherently complex; many aspects such as energy efficiency, limited resources, decentralized collaboration, fault tolerance have to be tackled. To be effective and to produce applicable results, fundamental research has to be tested, at least as a proof-of-concept, in large scale environments, so as to assess the feasibility of the new concepts, verify their large scale effects (not only at technological level, but also as for their foreseeable implications on users, society and economy) and derive further requirements, orientations and inputs for the research. In this paper we focus on the problems of interconnecting existing testbed environments via the Internet and providing a virtual unifying laboratory that will support academia, research centers and industry in their research on networks and services. In such a facility important issues of trust, security, confidentiality and integrity of data may arise especially for commercial (or not) organizations. In this paper we investigate such issues and present the design of a secure and robust architectural model for interconnecting testbeds of wireless sensor networks
Efficient and robust protocols for local detection and propagation in smart dust networks
No full textSmart Dust is a set of a vast number of ultra-small fully autonomous computing and communication devices, with very restricted energy and computing capabilities, that co-operate to quickly and efficiently accomplish a large sensing task. Smart Dust can be very useful in practice, i.e., in the local detection of a remote crucial event and the propagation of data reporting its realization. In this work we make an effort towards the research on smart dust from an algorithmic point of view. We first provide a simple but realistic model for smart dust and present an interesting problem, which is how to propagate efficiently information on an event detected locally. Then we present various smart dust protocols for local detection and propagation that are simple enough to be implemented on real smart dust systems, and perform, under some simplifying assumptions, a rigorous average case analysis of their efficiency and energy consumption (and their interplay). This analysis leads to concrete results showing that our protocols are very efficient and robust. We also validate the analytical results by extensive experiments. © 2005 Springer Science + Business Media, Inc
The dynamics of adaptive networked societies of tiny artefacts
No full textIn the near future, it is reasonable to expect that new types of systems will appear, of massive scale that will operating in a constantly changing networked environment. We expect that most such systems will have the form ofa large society of tiny networked artefacts. Angluin et al. [1] introduced the notion of "Probabilistic Population Protocols"(PPP) in order to model the behavior of such systems where extremely limited agents are represented as finite state machines that interact in pairs under the control ofan adversary scheduler. We propose to study the dynamics ofProba-bilistic Population Protocols, via the differential equations approach. We provide a very general model that allows to examine the continuous dynamics ofpopulation protocols and we show that it includes the model of [1], under certain conditions, with respect to the continuous dynamics of the two models. Our main proposal here is to exploit the powerful tools ofcontinuous nonlinear dynamics in order to examine the behavior ofsuch systems. We also provide a sufficient condition for stability. © 2008 IEEE
Distributed game-theoretic vertex coloring
No full textWe exploit the game-theoretic ideas presented in [12] to study the vertex coloring problem in a distributed setting. The vertices of the graph are seen as players in a suitably defined strategic game, where each player has to choose some color, and the payoff of a vertex is the total number of players that have chosen the same color as its own. We extend here the results of [12] by showing that, if any subset of non-neighboring vertices perform a selfish step (i.e., change their colors in order to increase their payoffs) in parallel, then a (Nash equilibrium) proper coloring, using a number of colors within several known upper bounds on the chromatic number, can still be reached in polynomial time. We also present an implementation of the distributed algorithm in wireless networks of tiny devices and evaluate the performance in simulated and experimental environments. The performance analysis indicates that it is the first practically implementable distributed algorithm. © 2010 Springer-Verlag
A probabilistic algorithm for efficient and robust data propagation in wireless sensor networks
No full textWe study the problem of data propagation in sensor networks, comprised of a large number of very small and low-cost nodes, capable of sensing, communicating and computing. The distributed co-operation of such nodes may lead to the accomplishment of large sensing tasks, having useful applications in practice. We present a new protocol for data propagation towards a control center ("sink") that avoids flooding by probabilistically favoring certain ("close to optimal") data transmissions. Motivated by certain applications (see [I.F. Akyildiz, W. Su, Y. Sankarasubramaniam, E. Cayirci, Wireless sensor networks: a survey, Journal of Computer Networks 38 (2002) 393-422], [C. Intanagonwiwat, R. Govindan, D. Estrin, Directed diffusion: a scalable and robust communication paradigm for sensor networks, in: 6th ACM/IEEE Annual International Conference on Mobile Computing (MOBICOM 2000), 2000, pp. 56-67]) and also as a starting point for a rigorous analysis, we study here lattice-shaped sensor networks. We however show that this lattice shape emerges even in randomly deployed sensor networks of sufficient sensor density. Our work is inspired and builds upon the directed diffusion paradigm of [C. Intanagonwiwat, R. Govindan, D. Estrin, Directed diffusion: a scalable and robust communication paradigm for sensor networks, in: 6th ACM/IEEE Annual International Conference on Mobile Computing (MOBICOM 2000), 2000, pp. 56-67]. This protocol is very simple to implement in sensor devices, uses only local information and operates under total absence of co-ordination between sensors. We consider a network model of randomly deployed sensors of sufficient density. As shown by a geometry analysis, the protocol is correct, since it always propagates data to the sink, under ideal network conditions (no failures). Using stochastic processes, we show that the protocol is very energy efficient. Also, when part of the network is inoperative, the protocol manages to propagate data very close to the sink, thus in this sense it is robust. We finally present and discuss large-scale simulation findings validating the analytical results. © 2005
A security model for internet-based digital asset management systems
No full textUsage and exploitation of the Internet is a critical requirement for managing and distributing valuable digital assets. This requirement introduces a great number of threats for commercial (or not) organizations that may cause huge data and financial losses, harm their reputation as well as people's trust on them. In this paper we present the research challenges for secure digital asset management over the web by proposing a model that provides data safety and secure user interaction on especially demanding on-line collaboration environments. © 2008 Springer-Verlag Berlin Heidelberg
An experimental study of basic communication protocols in ad-hoc mobile networks
No full textWe investigate basic communication protocols in ad-hoc mobile networks. We follow the semi-compulsory approach according to which a small part of the mobile users, the support Σ, that moves in a predetermined way is used as an intermediate pool for receiving and delivering messages. Under this approach, we present a new semi-compulsory protocol called the runners in which the members of Σ perform concurrent and continuous random walks and exchange any information given to them by senders when they meet. We also conduct a comparative experimental study of the runners protocol with another existing semi-compulsory protocol, called the snake, in which the members of Σ move in a coordinated way and always remain pairwise adjacent. The experimental evaluation has been carried out in a new generic framework that we developed to implement protocols for mobile computing. Our experiments showed that for both protocols only a small support is required for efficient communication, and that the runners protocol outperforms the snake protocol in almost all types of inputs we considered. © Springer-Verlag 2001
Smart Dust Protocols for Local Detection and Propagation
No full textSmart Dust is a set of a vast number of ultra-small fully autonomous computing and communication devices, with very restricted energy and computing capabilities, that cooperate to quickly and efficiently accomplish a large sensing task. Smart Dust can be very useful in practice i.e. in the local detection of a remote crucial event and the propagation of data reporting its realization. In this work we make an effort towards the research on smart dust from a basic algorithmic point of view. We first provide a simple but realistic model for smart dust and present an interesting problem, which is how to propagate efficiently information on an event detected locally. Then we present smart dust protocols for local detection and propagation that are simple enough to be implemented on real smart dust systems, and perform, under some simplifying assumptions, a rigorous average case analysis of their efficiency and energy consumption (and their interplay). This analysis leads to concrete results showing that our protocols are very efficient
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