9,350 research outputs found
On the Existence of an MVU Estimator for Target Localization with Censored, Noise Free Binary Detectors
The problem of target localization with censored noise free binary detectors
is considered. In this setting only the detecting sensors report their
locations to the fusion center. It is proven that if the radius of detection is
not known to the fusion center, a minimum variance unbiased (MVU) estimator
does not exist. Also it is shown that when the radius is known the center of
mass of the possible target region is the MVU estimator. In addition, a
sub-optimum estimator is introduced whose performance is close to the MVU
estimator but is preferred computationally. Furthermore, minimal sufficient
statistics have been provided, both when the detection radius is known and when
it is not. Simulations confirmed that the derived MVU estimator outperforms
several heuristic location estimators.Comment: 25 pages, 9 figure
A frequency-based RF partial discharge detector for low-power wireless sensing
Partial discharge (PD) monitoring has been the subject of significant research in recent years, which has given rise to a range of well-established PD detection and measurement techniques, such as acoustic and RF, on which condition monitoring systems for highvoltage equipment have been based. This paper presents a novel approach to partial discharge monitoring by using a low-cost, low-power RF detector. The detector employs a frequency-based technique that can distinguish between multiple partial discharge events and other impulsive noise sources within a substation, tracking defect severity over time and providing information pertaining to plant health. The detector is designed to operate as part of a wireless condition monitoring network, removing the need for additional wiring to be installed into substations whilst still gaining the benefits of the RF technique. This novel approach to PD detection not only provides a low-cost solution to on-line partial discharge monitoring, but also presents a means to deploy wide-scale RF monitoring without the associated costs of wide-band monitoring systems
Connectivity-Based Self-Localization in WSNs
Efficient localization methods are among the major challenges in wireless sensor networks today. In this paper, we present our so-called connectivity based approach i.e, based on local connectivity information, to tackle this problem. At first the method fragments the network into larger groups labeled as packs. Based on the mutual connectivity relations with their surrounding packs, we identify border nodes as well as the central node. As this first approach requires some a-priori knowledge on the network topology, we also present a novel segment-based fragmentation method to estimate the central pack of the network as well as detecting so-called corner packs without any a-priori knowledge. Based on these detected points, the network is fragmented into a set of even larger elements, so-called segments built on top of the packs, supporting even more localization information as they all reach the central node
Push & Pull: autonomous deployment of mobile sensors for a complete coverage
Mobile sensor networks are important for several strategic applications
devoted to monitoring critical areas. In such hostile scenarios, sensors cannot
be deployed manually and are either sent from a safe location or dropped from
an aircraft. Mobile devices permit a dynamic deployment reconfiguration that
improves the coverage in terms of completeness and uniformity.
In this paper we propose a distributed algorithm for the autonomous
deployment of mobile sensors called Push&Pull. According to our proposal,
movement decisions are made by each sensor on the basis of locally available
information and do not require any prior knowledge of the operating conditions
or any manual tuning of key parameters.
We formally prove that, when a sufficient number of sensors are available,
our approach guarantees a complete and uniform coverage. Furthermore, we
demonstrate that the algorithm execution always terminates preventing movement
oscillations.
Numerous simulations show that our algorithm reaches a complete coverage
within reasonable time with moderate energy consumption, even when the target
area has irregular shapes. Performance comparisons between Push&Pull and one of
the most acknowledged algorithms show how the former one can efficiently reach
a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks,
Springer. Animations and the complete code of the proposed algorithm are
available for download at the address:
http://www.dsi.uniroma1.it/~novella/mobile_sensors
How to Choose the Relevant MAC Protocol for Wireless Smart Parking Urban Networks?
Parking sensor network is rapidly deploying around the world and is regarded
as one of the first implemented urban services in smart cities. To provide the
best network performance, the MAC protocol shall be adaptive enough in order to
satisfy the traffic intensity and variation of parking sensors. In this paper,
we study the heavy-tailed parking and vacant time models from SmartSantander,
and then we apply the traffic model in the simulation with four different kinds
of MAC protocols, that is, contention-based, schedule-based and two hybrid
versions of them. The result shows that the packet interarrival time is no
longer heavy-tailed while collecting a group of parking sensors, and then
choosing an appropriate MAC protocol highly depends on the network
configuration. Also, the information delay is bounded by traffic and MAC
parameters which are important criteria while the timely message is required.Comment: The 11th ACM International Symposium on Performance Evaluation of
Wireless Ad Hoc, Sensor, and Ubiquitous Networks (2014
Optimal Fair Scheduling in S-TDMA Sensor Networks for Monitoring River Plumes
Underwater wireless sensor networks (UWSNs) are a promising technology to provide oceanographers with environmental data
in real time. Suitable network topologies to monitor estuaries are formed by strings coming together to a sink node.This network
may be understood as an oriented graph. A number of MAC techniques can be used in UWSNs, but Spatial-TDMA is preferred
for fixed networks. In this paper, a scheduling procedure to obtain the optimal fair frame is presented, under ideal conditions
of synchronization and transmission errors. The main objective is to find the theoretical maximum throughput by overlapping
the transmissions of the nodes while keeping a balanced received data rate from each sensor, regardless of its location in the
network. The procedure searches for all cliques of the compatibility matrix of the network graph and solves a Multiple-Vector
Bin Packing (MVBP) problem. This work addresses the optimization problem and provides analytical and numerical results for
both the minimum frame length and the maximum achievable throughput
Connectivity of confined 3D Networks with Anisotropically Radiating Nodes
Nodes in ad hoc networks with randomly oriented directional antenna patterns
typically have fewer short links and more long links which can bridge together
otherwise isolated subnetworks. This network feature is known to improve
overall connectivity in 2D random networks operating at low channel path loss.
To this end, we advance recently established results to obtain analytic
expressions for the mean degree of 3D networks for simple but practical
anisotropic gain profiles, including those of patch, dipole and end-fire array
antennas. Our analysis reveals that for homogeneous systems (i.e. neglecting
boundary effects) directional radiation patterns are superior to the isotropic
case only when the path loss exponent is less than the spatial dimension.
Moreover, we establish that ad hoc networks utilizing directional transmit and
isotropic receive antennas (or vice versa) are always sub-optimally connected
regardless of the environment path loss. We extend our analysis to investigate
boundary effects in inhomogeneous systems, and study the geometrical reasons
why directional radiating nodes are at a disadvantage to isotropic ones.
Finally, we discuss multi-directional gain patterns consisting of many equally
spaced lobes which could be used to mitigate boundary effects and improve
overall network connectivity.Comment: 12 pages, 10 figure
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