Results 11  20
of
72
Sensor networks deployment using flipbased sensors
 In Mobile Adhoc and Sensor Systems Conference, 2005. IEEE International Conference on
, 2005
"... ..."
(Show Context)
Communicating via fireflies: Geographic routing on dutycycled sensors
, 2007
"... Geographic routing is a useful and scalable pointtopoint communication primitive for wireless sensor networks. However, previous work on geographic routing makes the unrealistic assumption that all the nodes in the network are awake during routing. This overlooks the common deployment scenario whe ..."
Abstract

Cited by 19 (0 self)
 Add to MetaCart
(Show Context)
Geographic routing is a useful and scalable pointtopoint communication primitive for wireless sensor networks. However, previous work on geographic routing makes the unrealistic assumption that all the nodes in the network are awake during routing. This overlooks the common deployment scenario where sensor nodes are dutycycled to save energy. In this paper we investigate several important aspects of geographic routing over dutycycled nodes. First, we extend existing geographic routing algorithms to handle the highly dynamic networks resulting from dutycycling. Second, we provide the first formal analysis of the performance of geographic routing on dutycycled nodes. Third, we use this analysis to develop an efficient decentralized sleep scheduling algorithm for reducing the number of awake nodes while maintaining both network coverage and a (tunable) target routing latency. Finally, we evaluate via simulation the performance of our approach versus running existing geographic routing algorithms on sensors dutycycled according to previous sleep scheduling algorithms. Our results show, perhaps surprisingly, that a network of dutycycled nodes can have slightly better routing performance than a static network that uses comparable energy. Our results further show that, compared to previous algorithms, our sleep scheduling algorithm significantly improves routing latency and network lifetime.
Graphical Properties of Easily Localizable Sensor Networks
, 2006
"... The sensor network localization problem is one of determining the Euclidean positions of all sensors in a network given knowledge of the Euclidean positions of some, and knowledge of a number of intersensor distances. This paper identifies graphical properties which can ensure unique localizability ..."
Abstract

Cited by 18 (4 self)
 Add to MetaCart
The sensor network localization problem is one of determining the Euclidean positions of all sensors in a network given knowledge of the Euclidean positions of some, and knowledge of a number of intersensor distances. This paper identifies graphical properties which can ensure unique localizability, and further sets of properties which can ensure not only unique localizability but also provide guarantees on the associated computational complexity, which can even be linear in the number of sensors on occasions. Sensor networks with minimal connectedness properties in which sensor transmit powers can be increased to increase the sensing radius lend themselves to the acquiring of the needed graphical properties. Results are presented for networks in both two and three dimensions.
Understanding Node Localizability of Wireless Adhoc Networks
"... Abstract — Location awareness is highly critical for wireless adhoc and sensor networks. Many efforts have been made to solve the problem of whether or not a network can be localized. Nevertheless, based on the data collected from a working sensor network, it is observed that the network is NOT alw ..."
Abstract

Cited by 16 (5 self)
 Add to MetaCart
(Show Context)
Abstract — Location awareness is highly critical for wireless adhoc and sensor networks. Many efforts have been made to solve the problem of whether or not a network can be localized. Nevertheless, based on the data collected from a working sensor network, it is observed that the network is NOT always entirely localizable. Theoretical analyses also suggest that, in most cases, it is unlikely that all nodes in a network are localizable, although a (large) portion of the nodes can be uniquely located. Existing studies merely examine whether or not a network is localizable as a whole; yet two fundamental questions remain unaddressed: First, given a network configuration, whether or not a specific node is localizable? Second, how many nodes in a network can be located and which are them? In this study, we analyze the limitation of previous works and propose a novel concept of node localizability. By deriving the necessary and sufficient conditions for node localizability, for the first time, it is possible to analyze how many nodes one can expect to locate in sparsely or moderately connected networks. To validate this design, we implement our solution on a realworld system and the experimental results show that node localizability provides useful guidelines for network deployment and other locationbased services. I.
Fault tolerant connected sensor cover with variable sensing and transmission ranges
 in IEEE SECON
, 2005
"... Abstract — Sensor networks are often deployed in a redundant fashion. In order to prolong the network lifetime, it is desired to choose only a subset of sensors to keep active and put the rest to sleep. In order to provide fault tolerance, this small subset of active sensors should also provide some ..."
Abstract

Cited by 15 (1 self)
 Add to MetaCart
(Show Context)
Abstract — Sensor networks are often deployed in a redundant fashion. In order to prolong the network lifetime, it is desired to choose only a subset of sensors to keep active and put the rest to sleep. In order to provide fault tolerance, this small subset of active sensors should also provide some degree of redundancy. In this paper, we consider the problem of choosing a minimum subset of sensors such that they maintain a required degree of coverage and also form a connected network with a required degree of fault tolerance. In addition, we consider a more general, variable radii sensor model, wherein every sensor can adjust both its sensing and transmission ranges to minimize overall energy consumption in the network. We call this the variable radii k1Connected, k2Cover problem. To address this problem, we propose a distributed and localized Voronoibased algorithm. The approach extends the relative neighborhood graph (RNG) structure to preserve kconnectivity in a graph, and design a distributed technique to inactivate desirable nodes while preserving kconnectivity of the remaining active nodes. We show through extensive simulations that our proposed techniques result in overall energy savings in random sensor networks over a wide range of experimental parameters. I.
Improving Connectivity of Wireless AdHoc Networks
"... A fully connected topology is critical to many fundamental network operations in wireless adhoc networks. In this paper, we consider the problem of deploying additional wireless nodes to improve the connectivity of an existing wireless network. Specifically, given a disconnected wireless network, w ..."
Abstract

Cited by 14 (1 self)
 Add to MetaCart
A fully connected topology is critical to many fundamental network operations in wireless adhoc networks. In this paper, we consider the problem of deploying additional wireless nodes to improve the connectivity of an existing wireless network. Specifically, given a disconnected wireless network, we investigate how to deploy as few additional nodes as possible so that the augmented network can be connected. The problem is termed as the Connectivity Improvement (CI) problem. We first prove that CI is NPcomplete, and then present a Delaunay Triangulationbased algorithm, Connectivity Improvement using Delaunay Triangulation (CIDT). Depending on the priority based on which the components in a disconnected network should be chosen to connect, we devise several different versions of CIDT. We also present two additional optimization techniques to further improve the performance of CIDT. Finally, we verify the effectiveness of CIDT, and compare the performance of its variations via JSim simulation.
On the Critical Phase Transition Time of Wireless Multihop Networks with Random Failures
"... In this paper, we study the critical phase transition time of largescale wireless multihop networks when the network topology experiences a partition due to increasing random node failures. We first define two new metrics, namely the last connection time and first partition time. The former is the ..."
Abstract

Cited by 11 (4 self)
 Add to MetaCart
In this paper, we study the critical phase transition time of largescale wireless multihop networks when the network topology experiences a partition due to increasing random node failures. We first define two new metrics, namely the last connection time and first partition time. The former is the last time that the network keeps a majority of surviving nodes connected in a single giant component; while the latter is the first time that the remaining surviving nodes are partitioned into multiple small components. Then we analyze the devolution process in a geometric random graph of n nodes based on percolationtheory connectivity and obtain the sufficient condition under which the graph is percolated. Based on the percolation condition, the last connection time and first partition time are found to be on the same order. Particularly, when the survival function of node lifetime is exponential, they are on the order of log(log n); while if the survival function is Pareto, the order is (log n) 1/ρ, where ρ is the shape parameter of Pareto distribution. Finally, simulation results confirm that the last connection time and first partition time serve as the lower and upper bounds of the critical phase transition time, respectively. Further, an interesting result is that the network with heavytailed survival functions is no more resilient to random failures than the network with lighttailed ones, in terms of critical phase transition time, if the expected node lifetimes are identical.
Connectivity properties of largescale sensor networks
 WIRELESS NETWORKS
, 2009
"... In wireless sensor networks, both nodes and links are prone to failures. In this paper we study connectivity properties of largescale wireless sensor networks and discuss their implicit effect on routing algorithms and network reliability. We assume a network model of n sensors which are distribut ..."
Abstract

Cited by 10 (4 self)
 Add to MetaCart
In wireless sensor networks, both nodes and links are prone to failures. In this paper we study connectivity properties of largescale wireless sensor networks and discuss their implicit effect on routing algorithms and network reliability. We assume a network model of n sensors which are distributed randomly over a field based on a given distribution function. The sensors may be unreliable with a probability distribution, which possibly depends on n and the location of sensors. Two active sensor nodes are connected with probability pe(n) if they are within communication range of each other. We prove a general result relating unreliable sensor networks to reliable networks. We investigate different graph theoretic properties of sensor networks such as kconnectivity and the existence of the giant component. While connectivity (i.e. k = 1) insures that all nodes can communicate with each other, kconnectivity for k [ 1 is required for multipath routing. We analyze the average shortest path of the k paths from a node in the sensing field back to a base station. It is found that the lengths of these multiple paths in a kconnected network are all close to the shortest path.
The 2dimensional rigidity of certain families of graphs
 JOURNAL OF GRAPH THEORY
, 2005
"... Laman’s characterization of minimally rigid 2dimensional generic frameworks gives a matroid structure on the edge set of the underlying graph, as was first pointed out and exploited by L. Lovász and Y. Yemini. Global rigidity has only recently been characterized by a combination of two results du ..."
Abstract

Cited by 9 (1 self)
 Add to MetaCart
(Show Context)
Laman’s characterization of minimally rigid 2dimensional generic frameworks gives a matroid structure on the edge set of the underlying graph, as was first pointed out and exploited by L. Lovász and Y. Yemini. Global rigidity has only recently been characterized by a combination of two results due to T. Jordán and the first named author, and R. Connelly, respectively. We use these characterizations to investigate how graph theoretic properties such as transitivity, connectivity and regularity influence (2dimensional generic) rigidity and global rigidity and apply some of these results to reveal rigidity properties of random graphs. In particular, we characterize the globally rigid vertex transitive graphs, and show that a random dregular graph is asymptotically almost surely globally rigid for all d ≥ 4.