1,721,053 research outputs found
A sleep-awake protocol for information 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 continue our effort towards the research on smart dust from a basic algorithmic point of view. Under a simple but realistic model for smart dust we present an interesting problem, which is how to propagate efficiently information on an event detected locally. Then we present anew smart dust protocol, which we call the "Sleep-Awake" protocol, for information propagation that explicitly uses the energy saving features (i.e. the alteration of sleeping and awake time periods) of the smart dust particles. By using both some simple probabilistic analysis and extensive experiments, we provide some first concrete results for the success probability and the time and energy efficiency of the protocol, in terms of parameters of the smart dust network. We note that the study of the interplay of these parameters allows us to program the smart dust network characteristics accordingly. © 2003 IEEE
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
Modeling and evaluation of the effect of obstacles on the performance of wireless sensor networks
No full textIn this work, we propose an obstacle model to be used while simulating wireless sensor networks. To the best of our knowledge, this is the first time such an integrated and systematic obstacle model appears. We define several types of obstacles that can be found inside the deployment area of a wireless sensor network and provide a categorization of these obstacles, based on their nature (physical and communication obstacles), their shape, as well as their nature to change over time. In light of this obstacle model we conduct extensive simulations in order to study the effects of obstacles on the performance of representative data propagation protocols for wireless sensor networks. Our findings show that obstacle presence has a significant impact on protocol performance. Also, we demonstrate the effect of each obstacle type on different protocols, thus providing the network designer with advice on which protocol is best to use. © 2006 IEEE
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]
On the effect of user mobility and density on the performance of protocols for ad-hoc mobile networks
No full textIn this paper, we demonstrate the significant impact of (a) the mobility rate and (b) the user density on the performance of routing protocols in ad-hoc mobile networks. In particular, we study the effect of these parameters on two different approaches for designing routing protocols: (a) the route creation and maintenance approach and (b) the 'support' approach that forces few hosts to move, acting as 'helpers' for message delivery. We study one representative protocol for each approach, i.e. AODV for the first approach and RUNNERS for the second. We have implemented the two protocols and performed a large scale and detailed simulation study of their performance. The main findings are: the AODV protocol behaves well in networks of high user density and low mobility rate, while its performance drops for sparse networks of highly mobile users. On the other hand, the RUNNERS protocol seems to tolerate well (and in fact benefit from) high mobility rates and low densities. Copyright © 2004 John Wiley & Sons, Ltd
Fault-tolerant and efficient data propagation in wireless sensor networks using local, additional network information
No full textWe propose a new data dissemination protocol for wireless sensor networks, that basically pulls some additional knowledge about the network in order to subsequently improve data forwarding towards the sink. This extra information is still local, limited and obtained in a distributed manner. This extra knowledge is acquired by only a small fraction of sensors thus the extra energy cost only marginally affects the overall protocol efficiency. The new protocol has low latency and manages to propagate data successfully even in the case of low densities. Furthermore, we study in detail the effect of failures and show that our protocol is very robust. In particular, we implement and evaluate the protocol using large scale simulation, showing that it significantly outperforms well known relevant solutions in the state of the art. © 2007
Adaptive techniques for proactive collision avoidance for multi-path data propagation in wireless sensor networks
No full textData propagation in wireless sensor networks can be performed either by hop-by-hop single transmissions or by multi-path broadcast of data. Although several energy-aware MAC layer protocols exist that operate very well in the case of single point-to-point transmissions, none is especially designed and suitable for multiple broadcast transmissions. The key idea of our protocols is the passive monitoring of local network conditions and the adaptation of the protocol operation accordingly. The main contribution of our adaptive method is to proactively avoid collisions by implicitly and early enough sensing the need for collision avoidance. Using the above ideas, we design, implement and evaluate three different, new strategies for proactive adaptation. We show, through a detailed and extended simulation evaluation, that our parameter-based family of protocols for multi-path data propagation significantly reduce the number of collisions and thus increase the rate of successful message delivery (to above 90%) by achieving satisfactory trade-offs with the average propagation delay. At the same time, our protocols are shown to be very energy efficient, in terms of the average energy dissipation per delivered message. © 2006
Adaptive energy management for incremental deployment of heterogeneous wireless sensors
No full textWe introduce a new modelling assumption for wireless sensor networks, that of node redeployment (addition of sensor devices during protocol evolution) and we extend the modelling assumption of heterogeneity (having sensor devices of various types). These two features further increase the highly dynamic nature of such networks and adaptation becomes a powerful technique for protocol design. Under these modelling assumptions, we design, implement and evaluate a new power conservation scheme for efficient data propagation. Our scheme is adaptive: it locally monitors the network conditions (density, energy) and accordingly adjusts the sleep-awake schedules of the nodes towards improved operation choices. The scheme is simple, distributed and does not require exchange of control messages between nodes. Implementing our protocol in software we combine it with two well-known data propagation protocols and evaluate the achieved performance through a detailed simulation study using our extended version of the network simulator ns-2. We focus on highly dynamic scenarios with respect to network density, traffic conditions and sensor node resources. We propose a new general and parameterized metric capturing the trade-offs between delivery rate, energy efficiency and latency. The simulation findings demonstrate significant gains (such as more than doubling the success rate of the well-known Directed Diffusion propagation protocol) and good trade-offs achieved. Furthermore, the redeployment of additional sensors during network evolution and/or the heterogeneous deployment of sensors, drastically improve (when compared to "equal total power" simultaneous deployment of identical sensors at the start) the protocol performance (i.e. the success rate increases up to four times while reducing energy dissipation and, interestingly, keeping latency low). © 2007 Springer Science+Business Media, LLC
An adaptive compulsory protocol for basic communication in highly changing ad-hoc mobile networks
No full textIn this paper we study the problem of basic communication in ad-hoc mobile networks where the deployment area changes in a highly dynamic way and is unknown. We call such networks highly changing ad-hoc mobile networks. For such networks we investigate an efficient communication protocol which extends the idea (introduced in [4, 6]) of exploiting the co-ordinated motion of a small part of an ad-hoc mobile network (the "runners 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 fixed sized support for the whole duration of the protocol, to employ a support of some initial (small) size which adapts (given some time which can be made fast enough) to the actual levels of traffic and the (unknown and possibly rapidly changing) network area by changing its size in order to converge to an optimal size, thus satisfying certain Quality of Service criteria. We provide here some proofs of correctness and fault tolerance of this adaptive approach and we also provide analytical results using Markov Chains and random walk techniques to show that such an adaptive approach is, for this class of ad-hoc mobile networks, significantly more efficient than a simple non-adaptive implementation of the basic "runners support" idea. © 2002 IEEE
On the effect of user mobility and density on the performance of ad-hoc mobile networks
No full textIn this paper we demonstrate the significant impact of (a) the mobility rate and (b) the user density on the performance of routing protocols in ad-hoc mobile networks. In particular, we study the effect of these parameters on two different approaches for designing routing protocols: (a) the route creation and maintenance approach and (b) the "support" approach, that forces few hosts to move acting as "helpers" for message delivery. We study one representative protocol for each approach, i.e. AODV for the first approach and RUNNERS for the second. We have implemented the two protocols and performed a large scale and detailed simulation study of their performance. For the first time, we study AODV (and RUNNERS) in the 3D case. The main findings are: the AODV protocol behaves well in networks of high user density and low mobility rate, while its performance drops for sparse networks of highly mobile users. On the other hand, the RUNNERS protocol seems to tolerate well (and in fact benefit from) high mobility rates and low densities. Thus, we are able to partially answer an important conjecture of [7]. © 2004 IEEE
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