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41
Robust Distributed Network Localization with Noisy Range Measurements
, 2004
"... This paper describes a distributed, lineartime algorithm for localizing sensor network nodes in the presence of range measurement noise and demonstrates the algorithm on a physical network. We introduce the probabilistic notion of robust quadrilaterals as a way to avoid flip ambiguities that otherw ..."
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Cited by 292 (19 self)
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This paper describes a distributed, lineartime algorithm for localizing sensor network nodes in the presence of range measurement noise and demonstrates the algorithm on a physical network. We introduce the probabilistic notion of robust quadrilaterals as a way to avoid flip ambiguities that otherwise corrupt localization computations. We formulate the localization problem as a twodimensional graph realization problem: given a planar graph with approximately known edge lengths, recover the Euclidean position of each vertex up to a global rotation and translation. This formulation is applicable to the localization of sensor networks in which each node can estimate the distance to each of its neighbors, but no absolute position reference such as GPS or fixed anchor nodes is available. We implemented the algorithm on a physical sensor network and empirically assessed its accuracy and performance. Also, in simulation, we demonstrate that the algorithm scales to large networks and handles realworld deployment geometries. Finally, we show how the algorithm supports localization of mobile nodes.
Error Characteristics of Ad Hoc Positioning Systems (APS)
, 2004
"... APS algorithms use the basic idea of distance vector routing to find positions in an ad hoc network using only a fraction of landmarks, for example GPS enabled nodes. All the nodes in the network are assumed to have the possibility of measuring: range, angle of arrival (AOA), orientation, or a combi ..."
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Cited by 62 (0 self)
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APS algorithms use the basic idea of distance vector routing to find positions in an ad hoc network using only a fraction of landmarks, for example GPS enabled nodes. All the nodes in the network are assumed to have the possibility of measuring: range, angle of arrival (AOA), orientation, or a combination of them. We give a lower bound for positioning error in a multihop network for a range/angle free algorithm, and examine the error characteristics of four classes of multihop APS algorithms under various conditions, using theoretical analysis and simulations. Analysis of range/angle free, range based, angle based, and multimodal algorithms shows a complex tradeo# between the capabilities used, the density of the network, ratio of landmarks, and the quality of the positions obtained.
Entropybased Sensor Selection Heuristic for Target Localization
 in Proceedings of the third international symposium on Information processing in sensor networks
, 2004
"... We propose an entropybased sensor selection heuristic for localization. Given 1) a prior probability distribution of the target location, and 2) the locations and the sensing models of a set of candidate sensors for selection, the heuristic selects an informative sensor such that the fusion of the ..."
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Cited by 54 (1 self)
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We propose an entropybased sensor selection heuristic for localization. Given 1) a prior probability distribution of the target location, and 2) the locations and the sensing models of a set of candidate sensors for selection, the heuristic selects an informative sensor such that the fusion of the selected sensor observation with the prior target location distribution would yield on average the greatest or nearly the greatest reduction in the entropy of the target location distribution. The heuristic greedily selects one sensor in each step without retrieving any actual sensor observations. The heuristic is also computationally much simpler than the mutualinformationbased approaches. The e#ectiveness of the heuristic is evaluated using localization simulations in which Gaussian sensing models are assumed for simplicity. The heuristic is more e#ective when the optimal candidate sensor is more informative.
The nhop multilateration primitive for node localization problems
 Mobile Networks and Applications
, 2003
"... Abstract. The recent advances in MEMS, embedded systems and wireless communication technologies are making the realization and deployment of networked wireless microsensors a tangible task. In this paper we study node localization, a component technology that would enhance the effectiveness and capa ..."
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Cited by 48 (0 self)
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Abstract. The recent advances in MEMS, embedded systems and wireless communication technologies are making the realization and deployment of networked wireless microsensors a tangible task. In this paper we study node localization, a component technology that would enhance the effectiveness and capabilities of this new class of networks. The nhop multilateration primitive presented here, enables adhoc deployed sensor nodes to accurately estimate their locations by using known beacon locations that are several hops away and distance measurements to neighboring nodes. To prevent error accumulation in the network, node locations are computed by setting up and solving a global nonlinear optimization problem. The solution is presented in two computation models, centralized and a fully distributed approximation of the centralized model. Our simulation results show that using the fully distributed model, resource constrained sensor nodes can collectively solve a large nonlinear optimization problem that none of the nodes can solve individually. This approach results in significant savings in computation and communication, that allows finegrained localization to run on a low cost sensor node we have developed.
Mobileassisted localization in wireless sensor networks
 In Proceedings of IEEE INFOCOM ’05
, 2005
"... Abstract — The localization problem is to determine an assignment of coordinates to nodes in a wireless adhoc or sensor network that is consistent with measured pairwise node distances. Most previously proposed solutions to this problem assume that the nodes can obtain pairwise distances to other n ..."
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Cited by 46 (2 self)
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Abstract — The localization problem is to determine an assignment of coordinates to nodes in a wireless adhoc or sensor network that is consistent with measured pairwise node distances. Most previously proposed solutions to this problem assume that the nodes can obtain pairwise distances to other nearby nodes using some ranging technology. However, for a variety of reasons that include obstructions and lack of reliable omnidirectional ranging, this distance information is hard to obtain in practice. Even when pairwise distances between nearby nodes are known, there may not be enough information to solve the problem uniquely. This paper describes MAL, a mobileassisted localization method which employs a mobile user to assist in measuring distances between node pairs until these distance constraints form a “globally rigid ” structure that guarantees a unique localization. We derive the required constraints on the mobile’s movement and the minimum number of measurements it must collect; these constraints depend on the number of nodes visible to the mobile in a given region. We show how to guide the mobile’s movement to gather a sufficient number of distance samples for node localization. We use simulations and measurements from an indoor deployment using the Cricket location system to investigate the performance of MAL, finding in realworld experiments that MAL’s median pairwise distance error is less than 1.5 % of the true node distance. I.
Network localization in partially localizable networks
 in Proceedings of IEEE INFOCOM
, 2005
"... Abstract — Knowing the positions of the nodes in a network is essential to many next generation pervasive and sensor network functionalities. Although many network localization systems have recently been proposed and evaluated, there has been no systematic study of partially localizable networks, i. ..."
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Cited by 45 (10 self)
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Abstract — Knowing the positions of the nodes in a network is essential to many next generation pervasive and sensor network functionalities. Although many network localization systems have recently been proposed and evaluated, there has been no systematic study of partially localizable networks, i.e., networks in which there exist nodes whose positions cannot be uniquely determined. There is no existing study which correctly identifies precisely which nodes in a network are uniquely localizable and which are not. This absence of a sufficient uniqueness condition permits the computation of erroneous positions that may in turn lead applications to produce flawed results. In this paper, in addition to demonstrating the relevance of networks that may not be fully localizable, we design the first framework for two dimensional network localization with an efficient component to correctly determine which nodes are localizable and which are not. Implementing this system, we conduct comprehensive evaluations of network localizability, providing guidelines for both network design and deployment. Furthermore, we study an integration of traditional geographic routing with geographic routing over virtual coordinates in the partially localizable network setting. We show that this novel crosslayer integration yields good performance, and argue that such optimizations will be likely be necessary to ensure acceptable application performance in partially localizable networks. I.
The cricket indoor location system
, 2005
"... Indoor environments present opportunities for a rich set of locationaware applications such as navigation tools for humans and robots, interactive virtual games, resource discovery, asset tracking, locationaware sensor networking etc. Typical indoor applications require better accuracy than what c ..."
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Cited by 35 (0 self)
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Indoor environments present opportunities for a rich set of locationaware applications such as navigation tools for humans and robots, interactive virtual games, resource discovery, asset tracking, locationaware sensor networking etc. Typical indoor applications require better accuracy than what current outdoor location systems provide. Outdoor location technologies such as GPS have poor indoor performance because of the harsh nature of indoor environments. Further, typical indoor applications require different types of location information such as physical space, position and orientation. This dissertation describes the design and implementation of the Cricket indoor location system that provides accurate location in the form of user space, position and orientation to mobile and sensor network applications. Cricket consists of location beacons that are attached to the ceiling of a building, and receivers, called listeners, attached to devices that need location. Each beacon periodically transmits its location information in an RF message. At the same time,
Effects of correlated shadowing: Connectivity, localization, and RF tomography
 In ACM/IEEE Information Processing in Sensor Networks (IPSN
, 2008
"... Unlike current models for radio channel shadowing indicate, realworld shadowing losses on different links in a network are not independent. The correlations have both detrimental and beneficial impacts on sensor, ad hoc, and mesh networks. First, the probability of network connectivity reduces when ..."
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Cited by 22 (8 self)
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Unlike current models for radio channel shadowing indicate, realworld shadowing losses on different links in a network are not independent. The correlations have both detrimental and beneficial impacts on sensor, ad hoc, and mesh networks. First, the probability of network connectivity reduces when link shadowing correlations are considered. Next, the variance bounds for sensor selflocalization change, and provide the insight that algorithms must infer localization information from link correlations in order to avoid significant degradation from correlated shadowing. Finally, a major benefit is that shadowing correlations between links enable the tomographic imaging of an environment from pairwise RSS measurements. This paper applies measurementbased models, and measurements themselves, to analyze and to verify both the benefits and drawbacks of correlated link shadowing. 1.
Correlated link shadow fading in multihop wireless networks
 IEEE Trans. Wireless Commun
, 2009
"... Abstract—Accurate representation of the physical layer is required for analysis and simulation of multihop networking in sensor, ad hoc, and mesh networks. Radio links that are geographically proximate often experience similar environmental shadowing effects and thus have correlated shadowing. This ..."
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Cited by 20 (11 self)
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Abstract—Accurate representation of the physical layer is required for analysis and simulation of multihop networking in sensor, ad hoc, and mesh networks. Radio links that are geographically proximate often experience similar environmental shadowing effects and thus have correlated shadowing. This paper presents and analyzes a nonsitespecific statistical propagation model which accounts for the correlations that exist in shadow fading between links in multihop networks. We describe two measurement campaigns to measure a large number of multihop networks in an ensemble of environments. The measurements show statistically significant correlations among shadowing experienced on different links in the network, with correlation coefficients up to 0.33. Finally, we analyze multihop paths in three and four node networks using both correlated and independent shadowing models and show that independent shadowing models can underestimate the probability of route failure by a factor of two or greater. Index Terms—Wireless sensor, ad hoc, mesh networks, shadowing, correlation, statistical channel model, wireless communication, measurement, performance I.
Estimation bounds for localization
 in IEEE SECON
, 2004
"... for sensor networks. This paper studies the CramérRao lower bound (CRB) for two kinds of localization based on noisy range measurements. The first is Anchored Localization in which the estimated positions of at least 3 nodes are known in global coordinates. We show some basic invariances of the CRB ..."
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Cited by 16 (2 self)
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for sensor networks. This paper studies the CramérRao lower bound (CRB) for two kinds of localization based on noisy range measurements. The first is Anchored Localization in which the estimated positions of at least 3 nodes are known in global coordinates. We show some basic invariances of the CRB in this case and derive lower and upper bounds on the CRB which can be computed using only local information. The second is Anchorfree Localization where no absolute positions are known. Although the Fisher Information Matrix is singular, a CRBlike bound exists on the total estimation variance. Finally, for both cases we discuss how the bounds scale to large networks under different models of wireless signal propagation. Index Terms — CramérRao bound, localization, estimation bounds, ranging information, sensor networks.