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18
GPS free coordinate assignment and routing in wireless sensor networks
 In IEEE INFOCOM
, 2005
"... Abstract — In this paper we consider the problem of constructing a coordinate system in a sensor network where location information is not available. To this purpose we introduce the Virtual Coordinate assignment protocol (VCap) which defines a virtual coordinate system based on hop distances. As co ..."
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Abstract — In this paper we consider the problem of constructing a coordinate system in a sensor network where location information is not available. To this purpose we introduce the Virtual Coordinate assignment protocol (VCap) which defines a virtual coordinate system based on hop distances. As compared to other approaches, VCap is simple and have very little requirements in terms of communication and memory overheads. We compare by simulations the performances of greedy routing using our virtual coordinate system with the one using the physical coordinates. Results show that the virtual coordinate system can be used to efficently support geographic routing. Index Terms — Wireless sensor network, virtual coordinates, hop based greedy routing, performance analysis, simulations I.
Emergency guiding and monitoring applications in indoor 3D environments by wireless sensor networks
 Int. J. Sensor Netw. (IJSNet
, 2006
"... applications in indoor 3D environments by ..."
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Refining hopcount for localisation in wireless sensor networks
 International Journal of Sensor Networks
"... Abstract: Distance estimation is a crucial component in localisation for wireless sensor networks. Among the estimation methods, hopcount is widely used in situations where only connectivity information is available. However, hopcount is integervalued, implying crude distance estimation. In this ..."
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Abstract: Distance estimation is a crucial component in localisation for wireless sensor networks. Among the estimation methods, hopcount is widely used in situations where only connectivity information is available. However, hopcount is integervalued, implying crude distance estimation. In this paper, we refine hopcount to achieve better distance estimation. This is done by estimating neighbour distance and then approximating nonneighbour distance by the length of the shortest path. To estimate neighbour distance, we propose three estimators and show that they have negligible bias. We also show that the variance of the estimators is related to node density. The final refined hopcounts are further studied by simulations. Results verify the improvement on distance estimation and show that existing localisation methods can benefit from the improvement in various scenarios.
Emergence and Control of Macro Spatial Structures in Perturbed Cellular Automata, and Implications for Pervasive Computing Systems
 IEEE Transactions on Systems, Man, and Cybernetics – Part A
, 2005
"... Predicting the behavior of complex decentralized pervasive computing systems before their deployment in a dynamic environment, as well as being able to influence and control their behavior in a decentralized way, will be of fundamental importance in the near future. In this context, this paper descr ..."
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Predicting the behavior of complex decentralized pervasive computing systems before their deployment in a dynamic environment, as well as being able to influence and control their behavior in a decentralized way, will be of fundamental importance in the near future. In this context, this paper describes the general behavior observed in a large set of asynchronous cellular automata (CA) when external perturbations (expressions of a dynamic environment) influence the internal activities of CA cells. In particular, we observed that stable macrolevel spatial structures emerge from local interactions among cells, a behavior that does not emerge when cellular automata are not perturbed. Because perturbed cellular automata express characteristics that strongly resemble those of pervasive computing systems, similar sorts of macrolevel behaviors are likely to emerge in that context and need to be studied, controlled, and possibly fruitfully exploited. On this basis, the paper also reports the results of a set of experiments showing how it is possible to control, in a decentralized way, the behavior of perturbed cellular automata, to make some desired patterns emerge.
Empirical Characterization of Discretization Error in Gradientbased Algorithms
"... Many selforganizing and selfadaptive systems use the biologically inspired “gradient ” primitive, in which each device in a network estimates its distance to the closest device designated as a source of the gradient. Distance through the network is often used as a proxy for geometric distance, but ..."
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Many selforganizing and selfadaptive systems use the biologically inspired “gradient ” primitive, in which each device in a network estimates its distance to the closest device designated as a source of the gradient. Distance through the network is often used as a proxy for geometric distance, but the accuracy of this approximation has not previously been quantified well enough to allow predictions of the behavior of gradientbased algorithms. We address this need with an empirical characterization of the discretization error of gradient on random unit disc graphs. This characterization has uncovered two troublesome phenomena: an unsurprising dependence of error on source shape and an unexpected transient that becomes a major source of error at high device densities. Despite these obstacles, we are able to produce a quantitative model of discretization error for planar sources at moderate densities, which we validate by using it to predict error of gradientbased algorithms for finding bisectors and communication channels. Refinement and extension of the gradient discretization error model thus offers the prospect of greatly improving the engineerability of selforganizing systems on spatial networks. 1
Constraint and restoring force
, 2007
"... Longlived sensor network applications must be able to selfrepair and adapt to changing demands. We introduce a new approach for doing so: Constraint and Restoring Force. CRF is a physicsinspired framework for computing scalar fields across a sensor network with occasional changes. We illustrate ..."
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Longlived sensor network applications must be able to selfrepair and adapt to changing demands. We introduce a new approach for doing so: Constraint and Restoring Force. CRF is a physicsinspired framework for computing scalar fields across a sensor network with occasional changes. We illustrate CRF’s usefulness by applying it to gradients, a common building block for sensor network systems. The resulting algorithm, CRFGradient, determines locally when to selfrepair and when to stop and save energy. CRFGradient is selfstabilizing, converges in O(diameter) time, and has been verified experimentally in simulation and on a network of Mica2 motes. Finally we show how CRF can be applied to other algorithms as well, such as the calculation of probability fields. 1
and Problems—Geometrical problems and computations
, 2007
"... We present CRFGradient, a selfhealing gradient algorithm that provably reconfigures in O(diameter) time. Selfhealing gradients are a frequently used building block for distributed selfhealing systems, but previous algorithms either have a healing rate limited by the shortest link in the network o ..."
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We present CRFGradient, a selfhealing gradient algorithm that provably reconfigures in O(diameter) time. Selfhealing gradients are a frequently used building block for distributed selfhealing systems, but previous algorithms either have a healing rate limited by the shortest link in the network or must rebuild invalid regions from scratch. We have verified CRFGradient in simulation and on a network of Mica2 motes. Our approach can also be generalized and applied to create other selfhealing calculations, such as cumulative probability fields.
1VirtualCoordinateBased DeliveryGuaranteed Routing Protocol in Wireless Sensor Networks
"... Abstract—In this paper, we first propose a method, ABVCap, to construct a virtual coordinate system in a wireless sensor network. ABVCap assigns each node multiple 5tuple virtual coordinates. Subsequently, we introduce a protocol, ABVCap routing, to route packets based on the ABVCap virtual coordin ..."
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Abstract—In this paper, we first propose a method, ABVCap, to construct a virtual coordinate system in a wireless sensor network. ABVCap assigns each node multiple 5tuple virtual coordinates. Subsequently, we introduce a protocol, ABVCap routing, to route packets based on the ABVCap virtual coordinate system. ABVCap routing guarantees packet delivery without the computation and storage of the global topological features. Finally, we demonstrate an approach, ABVCap maintenance, to reconstruct an ABVCap virtual coordinate system in a network with node failures. Simulations show ABVCap routing ensures moderate routing path length, as compared to virtualcoordinate
Relation Between Gradients and Geographic Distances in Dense Sensor Networks with Greedy Message Forwarding
"... The distributed gradient protocol is a common building block to perform several tasks in a wireless sensor network. The gradient calculates the minimum hopdistances between each sensor and a specified set of anchor sensors. This calculation is performed using a distributed greedy forwarding of mes ..."
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The distributed gradient protocol is a common building block to perform several tasks in a wireless sensor network. The gradient calculates the minimum hopdistances between each sensor and a specified set of anchor sensors. This calculation is performed using a distributed greedy forwarding of messages in the network. Several virtual localization protocols use gradients to compute the virtual coordinates of the sensors. The quality of these coordinate systems depends on the relation between the value of the gradient and the real geographic distances between sensors. In this paper a formal proof of such relation is provided in the case of dense sensor networks with homogeneous sensor communication range r. The minimumhop distances between a sensor and an achor is bounded to be in a range defined by two geographic distances. The size of this range decreases with increasing density of the network and it is equal to the maximum resolution (the communication range r) when the density is high enough. 1.
and Problem Complexity]: Nonnumerical Algorithms and Problems—Geometrical problems and computations General Terms
"... We present CRFGradient, a selfhealing gradient algorithm that provably reconfigures in O(diameter) time. Selfhealing gradients are a frequently used building block for distributed selfhealing systems, but previous algorithms either have a healing rate limited by the shortest link in the network o ..."
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We present CRFGradient, a selfhealing gradient algorithm that provably reconfigures in O(diameter) time. Selfhealing gradients are a frequently used building block for distributed selfhealing systems, but previous algorithms either have a healing rate limited by the shortest link in the network or must rebuild invalid regions from scratch. We have verified CRFGradient in simulation and on a network of Mica2 motes. Our approach can also be generalized and applied to create other selfhealing calculations, such as cumulative probability fields. Categories and Subject Descriptors