Showing papers on "Wireless sensor network published in 1991"

Information integration and synchronization in distributed sensor networks

Abstract: The computational, i.e. architectural, algorithmic, and synchronization, issues related to competitive information integration in a distributed sensor network (DSN) are addressed. The proposed DSN architecture consists of a set of binary trees whose roots are fully connected. Each node of the tree has a processing element and one or more sensors associated with it. The information from each of the sensors has to be integrated in such a manner that the communication costs are low and that the real time needs are met. An information integration algorithm that has a low message cost (linear in the number of nodes of the network) and a low distributed computation cost is presented. The problems associated with synchronizing information to be integrated in the presence of imperfect clocks is considered. The fault tolerant features of the network and the integration algorithm are discussed. >

Enabling technologies for wireless in-building network communications-four technical challenges, four solutions

Abstract: A wireless in-building network is proposed, raising the possibility that at least part of the hard-wired infrastructure may no longer be needed. This wireless network is based on the refinement of cellular radio techniques in the 18 GHz range. The basic set of problems this technology addresses is described. These are the minimum performance and features required of a viable in-building wireless technology, the range of options available in selecting a design approach for such a system, and the technical problems that were faced in developing a microcellular wireless in-building system. >

Functional characterization of fault tolerant integration in distributed sensor networks

Abstract: Fault-tolerance is an important issue in network design because sensor networks must function in a dynamic, uncertain world. A functional characterization of the fault-tolerant integration of abstract interval estimates is proposed. This model provides a preliminary version for a general framework that is hoped to develop to address the general problem of fault-tolerant integration of abstract sensor estimates. A scheme for narrowing the width of the sensor output in a specific failure model is proposed and given a functional representation. The main distinguishing feature of the model over the original model of K. Marzullo (1989) is in reducing the width of the output interval estimate significantly in most cases where the number of sensors involved is large. >

Adaptive cell-averaging CFAR detection in distributed sensor networks

Abstract: The problem of adaptive cell-averaging constant false-alarm rate (CFAR) detection is considered for two distributed sensor network topologies, namely the parallel and the tandem topologies. The compressed data transmitted amongst the detectors is assumed to be in the form of decisions. The overall systems are optimized to yield the maximum probability of detection for a fixed probability of false alarm. The performance of the systems is also analyzed. >

Functional Characterization of Sensor Integration in Distributed Sensor Networks t

Abstract: Fault-tolerance is an important issue in network design because sensor networks must function in a dynamic, uncertain world. In this paper, we propose a functional characterization of the fault-tolerant integration of abstract interval estimates. This model provides a test bed for a general framework which we hope to develop to address the general problem of fault-tolerant integration of abstract sensor estimates. We further propose a scheme for narrowing the width of the sensor output in a specific failure model and give it a functional representation. The main distinguishing feature of our model over the original Marzullo's model is in reducing the width of the output interval estimate significantly in most cases where the number of sensors involved is large.

Functional characterization of sensor integration in distributed sensor networks

Abstract: Fault-tolerance is an important issue in network design because sensor networks must function in a dynamic, uncertain world. In this paper, the authors propose a functional characterization of the fault-tolerant integration of abstract interval estimates. This model provides a test bed for a general framework which the authors hope to develop to address the general problem of fault-tolerant integration of abstract sensor estimates. They further propose a scheme for narrowing the width of the sensor output in a specific failure model and give it a functional representation. The main distinguishing feature of the authors' model over the original Marzullo's model is in reducing the width of the output interval estimate significantly in most cases where the number of sensors involved is large. >

A hierarchy of network-based knowledge systems

Abstract: An extension of the method that was used for building and using the network-based knowledge system SUPER is proposed to fully utilize the benefits of this approach in the domain of diagnosing distributed dynamically evolving processes. In the scope of distributed sensor networks, several issues are addressed concerning problems dealing with software architectures, strategies, and properties for efficient sensor data management: (1) how to build links efficiently between the elements of each network-based knowledge base, (2) how to maintain consistency of the whole structure and manage the constraints of domain dependent variables corresponding to sensor data, (3) how to manage and update efficiently the database at run time in order to maintain its consistency and to satisfy a high level of response time performances, and (4) how to propagate the solutions given by a qualitative knowledge base into a knowledge base utilizing sensor data whenever the sensors are out of order. The answers given are based on extending and generalizing the principles that have been defined for SUPER. >

Sensor system eg for chlorofluorocarbons (CFCs)

Abstract: A sensor system compares a measurement of CFC concentration with a stored threshold value which varies with time according to predicted variations in the background concentration of CFCs, thus avoiding unwanted alarm output signals caused by high background values. A CFC detector 2a has a housing including a detection section 13 containing a sensor. A fan is also located within the housing, and forces air past the sensor at a known rate, ensuring that the quantity of CFCs present can be measured accurately. A sensor network includes a number of base stations, each connected to a central processor, to which sensors (2a-2c, 3a-3c, 4a-4c, Figure 1) are interchangeably connected. The sensors may be CFC detectors, or pressure or temperature sensors providing data relevant to the control of the heating or air conditioning system in a building.

Topological analysis of satellite-based distributed sensor networks

Abstract: A method for evaluating the topological quality of networks for distributed sensor applications is presented. The criteria for evaluation are network survivability and delay. Nodal connectivity is used to characterize survivability, and mean path length is used to characterize delay. To calculate these two quantities, an algorithm is developed to find k shortest node-disjoint paths between a pair of nodes when each link has unit distance. The effects of nodal losses in a multiple-node satellite network consisting of a Walker low-orbit sphere and a geosynchronous constellation are examined. The example demonstrates how topological analysis on the basis of connectivity and mean path length may be used to detect, and subsequently to address, potential flaws in a network design. The results show that the geosynchronous/low-orbit link assignment protocol should be a primary concern in the design of this network. They also show that the nodal degree of a failed node, and the distribution of links between the Walker sphere and the geosynchronous constellation, are the fundamental determinants of mean path length. >

Fiber optic sensor networks

Abstract: The detailed topological requirements for each fiber optic sensor system differ, but there are many general features, particularly concerning the power distribution between sensor elements and the collection of the data in the optical domain, which are common to all systems. This paper highlights these general features.

Multibit optical sensor networking

Abstract: The optical fiber sensor networking problem is considered from a digital communication viewpoint. A multibit, all-optical temperature sensor design concept is presented. The sensor generates 2M codewords of length M bits (gray coded), each codeword corresponding to a specific temperature threshold within 1-2 deg accuracy. The codewords are generated serially, and therefore only a single output fiber line is required. The proposed sensor design is used in conjunction with a time division multiplexing (TDM) scheme to verify the concept of multibit sensor multiplexing and networking. In addition, sensor array design to multiplex multibit optical sensors is presented, and the trade-offs between the maximum number of sensors, system power margin, bit rates generated by the sensor arrays, and the fiber delay lines necessary for TDM are discussed. Finally, the network architectures (similar to LAN topologies) and the processes necessary at the remote receiver to recover the sensing information from each individual multibit sensor are explained.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Method and device for measuring position of underground excavator

Abstract: PURPOSE:To enable execution of automatic and efficient measurement in real time even when a planned line of a tunnel extends at a long distance or curves, by a method wherein a change in a magnetic force on the basis of a magnetism generating means is detected by a magnetic sensor network formed of a plurality of magnetic sensors provided above a line of excavation. CONSTITUTION:A magnetic sensor network 12 formed of a plurality of magnetic sensors 10 for detecting a change in magnetism in the ground is provided above a line of excavation of an underground excavator 20. A change in a magnetic force based on a magnet 22 of a magnetism generating means attached to the excavator 20 is detected by the sensor network 12 and a plane position of the excavator 20 is detected therefrom. In other words, the excavator 20 having the magnet 22 attached thereto is passed under the sensor network 12 and the magnetism of the magnet 22 can be detected as an external magnetism by the sensors 10 positioned above. According to this method, the position of the excavator 20 within a horizontal plane can be detected from the relative positions of the sensor network 12 having the known coordinates and the sensors 10.