Showing papers on "Wireless sensor network published in 1998"

Wireless integrated network sensors: Low power systems on a chip

Abstract: Wireless Integrated Network Sensors (WINS) now provide a new monitoring and control capability for transportation, manufacturing, health care, environmental monitoring, and safety and security WINS combine sensing, signal processing, decision capability, and wireless networking capability in a compact, low power system WINS systems combine microsensor technology with low power sensor interface, signal processing, and RF communication circuits The need for low cost presents engineering challenges for implementation of these systems in conventional digital CMOS technology This paper describes micropower data converter, digital signal processing systems, and weak inversion CMOS RF circuits The digital signal processing system relies on a continuously operating spectrum analyzer Finally, the weak inversion CMOS RF systems are designed to exploit the properties of high-Q inductors to enable low power operation This paper reviews system architecture and low power circuits for WINS

Wireless integrated sensor network using multiple relayed communications

Abstract: Wireless integrated miniature sensing stations which can be organized into a communicating network allow sensitive detection and analysis of vibration, infrared radiation, sound, or other physical signals indicative of an intruder or condition to be monitored over a wide area. The sensing stations operate on low power and include a sensor or sensors, a digital signal processor, a microprocessor, and a wireless transceiver for communication. Network communication is facilitated by multiple relayed transmissions from station to station.

Wireless sensor networks

Abstract: Advances in commercial IC fabrication technology have made possible the integration of wireless transceivers, CMOS signal processing, and sensing in one integrated circuit package. Combination with actuation is also possible. This amounts to a low-cost means to link communications and computer networks to the physical world, and may have profound consequences in such diverse areas as security, process control, planetary exploration, and medical monitoring and diagnosis. We outline the system design issues for a distributed sensor network, in which each node has a limited energy supply and relatively low data rate link. The nodes must establish a synchronous multi-hop network, determine locations, and cooperate for such purposes as beamforming and passing messages to the outside world.

Network awareness and mobile agent systems

Abstract: Most current computer applications are insensitive to changing network conditions. With the growing demand for wireless, satellite, and other highly volatile computer communications networks, however, applications that are robust in the presence of network volatility must be designed and built. Network-robust applications are of great interest in military situations today, and we expect that interest to grow in industrial and eventually consumer environments as well. Mobile agents are one way to realize such applications, especially when used in a wireless environment. This article discusses issues and results related to the problem of making computer applications network-aware and reactive to changing network conditions. It contains a short overview of our work on mobile agents as well as a tutorial on network sensing from the agent perspective. Some prototypes of network sensing systems and network aware mobile-agent applications are presented.

A modular, wireless network platform for monitoring structures

Abstract: Continuous monitoring of structures has recently become an area of great activity in both the research community and commercial sector. The vast majority of published work has focused on developing algorithms to advance the detection and diagnosis of structures. An equally important task is the establishment of a flexible hardware platform capable of real-time data acquisition. Many of the existing monitoring strategies assume a sophisticated hardware infrastructure. Such an assumption ignores the issues of up-front cost, relative total cost/information benefit, system installation, and life-time maintenance. A multidisciplinary research program at Stanford University, between the Electrical, Mechanical, and Civil Engineering Departments, has developed a hardware platform based on embedded systems and wireless networks to realize the needs of the monitoring community. Our approach has been to determine the desired qualities of a structural monitoring system and design both the hardware to acquire and manage such data and the software to facilitate damage detection diagnosis. A monitoring platform based on embedded systems and wireless packet-switching networks allows for a relatively low-cost, unobtrusive, and maintainable network of sensor units. The embedded system approach pushes intelligence forward in the monitoring system, relieving the data acquisition and computational burden of a central computer and enabling local decision analysis and data processing. A wireless packet-switched network eliminates cabling installation, cable maintenance, and signal degradation over long distances. A functional network of sensor units is demonstrated. The hardware and software co-design issues are addressed. The implications for practical deployment using such a network of modular units are discussed.

Hierarchical information processing in distributed sensor networks

Abstract: It is now possible to integrate in a very small and low cost package sensing, actuation, signal processing, and radio communications. This new technology will make possible the low cost interfacing of the physical world to information processing and telecommunications networks. We describe the particular application of distributed sensor networks which must convey decisions to and from a remote center, and how information processing and communications can be organized so that the network is scalable and low power. Information theoretic problems are stated in the areas of detection, rate distortion, and channel coding.

Intelligent distributed sensor network

Abstract: The intelligent functions of sensor measurement instrumentation are formed on basis of the original calibration and prediction methods. Measuring module structure as basic distributed sensor network (DSN) component is considered and an intelligent DSN (IDSN) structure is proposed. Procedures and functions of various levels of information processing in IDSN are formed. Developed IDSN is tested on design and exploitation stages.

Apparatus method and systems relating to a wireless geographical positioning system including a system for monitoring and analyzing characteristics of a wireless telecommunications network

Abstract: Apparatus, methods and systems related to, or employing, an event detector that causes a wireless telecommunications network to trigger a request to a wireless positioning system upon detecting a predefined event associated with a Mobile System (MS); the wireless positioning system is operable to determine and communicate the geographic location of the MS to the wireless telecommunications network in response to receiving the request. A system for monitoring and analyzing characteristics of a wireless telecommunications network can advantageously employ the event detector to log data associated with each occurrence of a predefined event. The data can be displayed on a video terminal, for example, as a graphical representation of the data; the graphical representation can be an overlay of the data on a topographical representation of at least a portion of the wireless telecommunications network, whereby the characteristics can be used to troubleshoot and/or improve the operation of the wireless telecommunications network.

Man-portable networked sensor system

Abstract: The Man-Portable Networked Sensor System (MPNSS), with its baseline sensor suite of a pan/tilt unit with video and FLIR cameras and laser rangefinder, functions in a distributed network of remote sensing packages and control stations designed to provide a rapidly deployable, extended-range surveillance capability for a wide variety of security operations and other tactical missions. While first developed as a man-portable prototype, these sensor packages can also be deployed on UGVs and UAVs, and a copy of this package been demonstrated flying on the Sikorsky Cypher VTOL UAV in counterdrug and MOUNT scenarios. The system makes maximum use of COTS components for sensing, processing, and communications, and of both established and emerging standard communications networking protocols and system integration techniques. This paper will discuss the technical issues involved in: (1) system integration using COTS components and emerging bus standards, (2) flexible networking for a scalable system, and (3) the human interface designed to maximize information presentation to the warfighter in battle situations.

Multiplexing Techniques for Noninterferometric Optical Point-Sensor Networks: A Review

Abstract: This article presents a review of the strategies that have been both demonstrated and proposed for the multiplexing of multiple noninterferometric optical fiber point sensors to form a sensor network. The focus, which avoids consideration of interferometric sensor types, enables discussion of conventional multiplexing tech niques, namely, spatial, time division, frequency division, and wavelength division prior to dealing with combined or hybrid schemes, which exhibit the potential for increased multiplexing gain. Specific advantages and potential drawbacks of the different strategies are provided together with an indication of the number of point sensors that each multiplexing scheme can support.

U.S. Space Surveillance Network capabilities

Abstract: The US Space Command maintains a positional catalog of over 8000 man-made space objects The basis of this catalog is the observational data collected by a worldwide network of radars and optical sites known collectively as the US Space Surveillance Network which is operated by the US Air Force, Army and Navy This network was developed following the launch of the first SPUTNIK in 1957 at which time the Air Force was given the task by the US Congress of maintaining a catalog of all the detectable objects in space-active and inactive satellites, spent boosters and other miscellaneous jetsam that constitute the dangerous portion of the space debris population The fundamental mission of the space surveillance network is to keep reliable, up-to-date information on all detectable resident space objects (RSOs) in space The sensors in the network are primarily ground-based except for a recent sensor that was deployed in space The capabilities of the network are described in this paper Specific examples will be used to demonstrate that the space surveillance network constitutes a capable and extensive remote sensing system for resident space objects and debris

Low-complexity digital encoding strategies for wireless sensor networks

Abstract: Low-complexity schemes for digital encoding of a noise-corrupted signal and associated signal estimators are presented. This problem arises in wireless distributed sensor networks where an environmental signal of interest is to be estimated at a central site from low-bandwidth digitized information received from collections of remote sensors. We show that the use of a properly designed and often easily implemented additive control input before signal quantization can significantly enhance overall system performance. In particular, efficient estimators can be constructed and used with optimized pseudo-noise, deterministic, and feedback-based control inputs, resulting in a hierarchy of practical systems with very attractive performance-complexity characteristics.

Wireless QoS analysis for a Rayleigh fading channel

Abstract: We present an analysis of the relationship between the two link-level QoS (quality of service) parameters (delay and error rate) and the motion speed of a user in a wireless packet network environment. The analysis is based on: (1) a wireless channel simulation using a time-correlated Rayleigh fading model and (2) a physical layer model which complies with the wireless LAN draft standard, IEEE 802.11. The analysis on delay and error rate QoS parameters is targeted to two major types of network applications: (1) real-time applications which are sensitive to delay but can tolerate a small amount of data loss and (2) conventional data transfer applications which are sensitive to data loss but normally do not require specific delay bounds.

Distributed and autonomous sensing based on the immune network

Abstract: A distributed and autonomous sensor network is proposed based on the informational features of the immune network: recognition of nonself by distributed and dynamically interacting units, recognition by a simple comparison with the units themselves, dynamic propagation of activation that would lead to system-level recognition, and memory embedded as stable equilibrium states in the dynamic network. The network is explained by an illustrative example of an eight-coin puzzle: a balance must be used only three times to identify one coin with a different weight from the other seven coins. Our network also uses a dynamic structure network rather than the fixed structures used in neural networks. Simulations show that nonself (the different coin in the eight-coin puzzle, the sensor/process fault in the monitoring example) will be identified by dynamically propagating activation through the network.

Experimental evaluation of channel state dependent scheduling in an in-building wireless LAN

Abstract: Wireless links are often subject to burst errors leading to consecutive packet losses, which could be buffered and transmitted later, giving priority to packets on stronger links. This improves overall bandwidth utilization. A channel state dependent scheduling protocol based on the above idea is developed and implemented in a wireless LAN. A commercial wireless LAN, Lucent Technology's Wavelan, is used with Pentium based laptops and PCs. The protocol is implemented as a part of the device driver in the Linux operating system. The protocol includes a channel sensing mechanism to help determine when a wireless link comes out of the error state. Experimental performance evaluation with UDP streams and FTP sessions demonstrates the significant performance benefits of channel state dependent scheduling. The performance evaluation includes a novel channel modulation technique based on previously collected traces for reproducibility of experiments.

Time-frequency and time-scale representation of wireless communication channels

Abstract: Time-frequency and time-scale representation techniques play an important role for wireless communication applications where the channel is a time-varying system. It is shown in this paper that those variations can be tracked by a dynamic spectral multiresolution analysis. We also quantify the effects of channel parameters on bandwidth efficiency of wireless channel this paper.

A highly miniaturized, battery operated, commandable, digital wireless camera

Abstract: This paper discusses the design, development, testing, and demonstration of a highly miniaturized battery operated, digital wireless camera. The miniature wireless camera receives commands transmitted from a remote base station requesting it to take one or more frames of data, and broadcasts the digital image data to the base station receiver for display. The camera uses a complementary metal-oxide-semiconductor (CMOS) active pixel image sensor (APS) that achieves noise performance comparable to a charge-coupled device (CCD) with orders of magnitude better power consumption performance. The image sensor is integrated with a wireless communications transceiver, antennas and batteries into a stand alone miniature package. The results of a three year development effort are described.

Object-Oriented Concept Classification of Large Measurement Data Sets in Civil Structures

Abstract: In the last few years the concept of “smart structures” has become increasingly attractive to the civil engineering community. A variety of strain, displacement, temperature and chemical sensors have been proposed and some have been successfully tested in the field. However, a well designed or quality network of sensors does not increase by itself the security and knowledge of the structure if it is not accompanied by a serious classification and analysis of the measurements. In the case of long term monitoring of civil structures, the sensors are not always installed at the same time, and therefore the classification and determination of the measurement reference is a real problem. By subdividing the whole structure and its sensor network into structural elements and those further into cells combining a group of sensors, it is possible to obtain a hierarchy of objects which can be analyzed independently. The characteristics of an object are defined by those of its elements. This modular method based on the object-oriented-concept is very easy to handle. It is possible to use different models (and associated algorithms) to d etermine the characteristics of an object from its elements. An automatic diagnostic of the model is also possible and the method finds proposes the optimum model and algorithm for a given structure and situation.

An efficient media access control protocol for delay sensitive bursty data in broadband wireless networks

Abstract: Media access control (MAC) for broadband wireless networks is a hard and important problem. Previous studies on this problem suggested using reservations and demand assignments, i.e., mobile terminals (MTs) send requests to the base station (they may contend with each other for the access) to reserve transmission resources (time slots, codes, etc.) when they have data to send. These protocols may cause degradation of QoS, due to the fact that MTs could fail frequently competing for the access. Especially, these protocols can not meet the QoS requirements of delay sensitive and bursty data. We propose a novel MAC protocol which uses transmission collision as a useful information for random access. Analysis shows it overcomes the above mentioned problem (and thus guarantees better QoS) while consuming less wireless resources and system overhead.

Array signal processing for a wireless MEM sensor network

Abstract: We first review the high-level signal processing architecture of a wireless MEM sensor system for source detection, signal enhancement, localization, and identification. A blind beamformer using only the measured data of randomly distributed sensors to form a sample correlation matrix is proposed. The maximum power collection criterion is used to obtain array weights from the dominant eigenvector of the sample correlation matrix. An effective blind beamforming estimation of the time delays of the dominant source is demonstrated. Source localization based on a novel least-squares method for time delay estimation is also given. Array system performance based on analysis, simulation, and measured acoustical/seismic sensor data is presented. Applications of such a system to multimedia, intrusion detection, and surveillance are briefly discussed.

Lidar as part of an ROV-based sensor network for the detection of chemical pollutants on the seafloor

Abstract: The seafloor may be polluted by hazardous chemicals in different forms, e.g., as a sinker pool or stored in a sunken container. Although techniques exist for a recovery, instruments for the detection, especially in turbid waters, are still unsuitable. The variety of substances and scenarios requires a number of strategies based on different physical and chemical principles. To complete the existing surveillance system in the German Bight, the German Ministry of Transport intends to operate an ROV which can be equipped with instruments for in situ water analysis and remote sensing of the seafloor. Besides commercially available sensors like CTD probes, the system includes several newly developed underwater instruments: gas chromatography and mass spectrometry, quartz microbalance detectors, acoustic sensor for impedance measurements and lidar. Instruments and control unit on board the operating ship are connected to a database via ethernet which allows for a fast and efficient combined data interpretation. One of the remote sensing instruments integrated in the payload of the ROV is a submarine lidar. It is a combination of a range gating video camera and a fluorescence lidar. The range gating video camera takes contrast enhanced images from the seafloor in turbid waters. Therefore it is used to search for and-in case of success-to inspect lost containers on the ground. The fluorescence lidar is used to detect chemicals which are normally invisible on video images. The analysis of fluorescence spectra allows substances to be classified.

Efficient digital encoding and estimation of noisy signals

Abstract: : In many applications in science and engineering one must rely on coarsely quantized and often unreliable noisy measurements in order to accurately and reliably estimate quantities of interest. This scenario arises, for instance, in distributed wireless sensor networks where measurements made at remote sensors need to be fused at a host site in order to decipher an information-bearing signal. Resources such as bandwidth, power, and hardware are usually limited and shared across the network. Consequently, each sensor may be severely constrained in the amount of information it can communicate to the host and the complexity of the processing it can perform. In this thesis, we develop a versatile framework for designing low-complexity algorithms for efficient digital encoding of the measurements at each sensor, and for accurate signal estimation from these encodings at the host. We show that the use of a properly designed and often easily implemented control input added prior to signal quantization can significantly enhance overall system performance. In particular, efficient estimators can be constructed and used with optimized pseudo-noise, deterministic, and feedback-based control inputs, resulting in a hierarchy of practical systems with very attractive performance-complexity characteristics.

Static and dynamic bridge monitoring with fiber optic sensors

Abstract: In many concrete bridges, deformations due to static and dynamic loading are the most relevant parameters to be monitored in both the short and long term. Strain monitoring give only local information about the material behavior and too many of such sensor are therefore necessary to gain a complete understanding of the bridge evolution. Recent advances in measurement technology have demonstrated that optical fiber sensors are suitable for monitoring full-scale structures. A network of such sensors installed inside a bridges enables the measurement of parameters such as internal deformation and temperature. In the past four years, our laboratory has installed hundreds of fiber optic deformation sensors of varying seizes in concrete and composite steel-concrete bridges. These sensors give useful information during the construction phases and about the long-term geometrical deformations of a bridge under static load. Recently it has been found that these sensors can also be used to measure the quasi-static part of the dynamic deformation of a bridge under traffic load. The measurement technique relies on low-coherent interferometry and it guarantees high resolution, high precision ad long-term stability. Nevertheless each measurement takes a few seconds, thus it is inadequate for monitoring the dynamic behavior of bridges, where measurement frequencies of up to 1 kHz are necessary. This paper also presents a new technique to demodulate at a high frequency of up to 1 kHz are necessary. This paper also presents a new technique to demodulate at a high frequency the signal for the same sensors used for long-term monitoring. With its large dynamic range of several mm it allows for the monitoring of bridges under dynamic loads while maintaining the configuration of the original fiber optic sensor that has been proven to be reliable.

Multipoint fibre sensors for trace gas monitoring using derivative spectroscopy

Abstract: A number of important gases in the context of environmental and safety issues possess absorption lines in the near-IR region of the spectrum between 1 and 2 micrometers . These include gases such as carbon monoxide, carbon dioxide, hydrogen sulphide and methane. The availability of low cost communications fiber and components such as connectors and couplers make this spectral region attractive for the development of fiber sensor networks for continuous monitoring of trace gases. However, the absorption lines are weak and careful design of the modulation and signal processing schemes are required in order to obtain adequate sensitivities for commercial application. Furthermore the laser source must operate around the specific wavelength of the gas absorption line and the resulting high cost of manufacture needs to be mitigated by arranging for a large number of sensor locations within the fiber network. Here we illustrate how the above concerns can be met in the case of methane gas where we have developed a multi-point sensor network with adequate sensitivity for safety monitoring.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Framework for implementing self-organizing task-oriented multisensor networks

Abstract: Advanced manipulation skills that enable cooperating robots in a work cell to recognize, handle and assemble arbitrarily placed objects require sensory information on both the environment and the assembly process. Using standard approaches it becomes difficult to coordinate sensor usage and data fusion under a given task when the number of sensors becomes large or is changed during run-time. We present a solution to both coordination and fusion based on the multi (sensor) agent paradigm: each agent implements a sensory skill, a negotiation protocol and a physical communication interface to all other agents. Within this sensor-network teams cooperate on a common task. They are formed dynamically after a negotiation phase following a specific task formulation. Our framework consists of a formal specification of the requirements that the sensory skill of an agent has to meet and a comprehensive library of (C++)-objects encapsulating all of the negotiation protocol and communications. This separation makes it very easy to implement individual sensory skills. We show how the abstract concepts of this approach and the metaphor of `negotiation' work in a real-world network: several uncalibrated cameras are used to guide a manipulator towards a target. We also show how agent-teams may easily (self- )reconfigure during task execution in the case of unexpected events. The framework is distributed free of charge and can be obtained over the Internet at http://magic.uni- bielefeld.de.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Handoff routing strategies and mobility in multicarrier wireless networks

Abstract: An analytical model for a wireless system composed of several wireless networks working with different carriers and sharing the resources to give a better service to their users when handing off is introduced. We use capacity, overload, reservation and mobility variables to characterize the wireless network, which is modeled as a network of queues. We propose some methods for allocation, of the resources, namely sequential, uniform and m-uniform schemes. We found that m-uniform scheme improves the performance in the network by allowing overflow of users from a carrier to be offered as traffic into other cells of other carriers.

Communication architecture to support distributed sensors

Abstract: This paper explores a queuing approach to quantifying the delay performance bounds of a distributed sensor network in response to the number of targets or events to be observed and communicated through the network. Employing a simple sensor fusion and a priority queuing model of the delay effects of processing and communication, we analyse node delay performance. We extend the node model through analysis of information flows with neighbour nodes to examine characteristics of the network. We discuss means of extending network performance through the use of alternate queuing disciplines.

Distributed event-driven architectures for evolutionary sensor fusion

Abstract: The next decade will require the development of complex sensor systems that integrate data from a large number of sensor elements. Such systems will play important roles in a wide variety of industrial and defense systems, as the fusion of multiple sources of information is crucial to sensor operation in noisy environments, and in complex decision making. The arrival of ubiquitous processing elements is one requirement for the development of such systems; however, the ability to connect and integrate these elements at the logical level is the more limiting aspect of their development. Furthermore, it is unlikely that such systems can be developed in a single linear process. It is much more probable that such systems will need to be evolved over time, perhaps a substantial period of time, and as result the ability to logically interconnect heterogeneous elements in an evolutionary manner will be of great importance. This paper outlines some approaches to this problem based on the distributed object-computing model as introduced in the OMG CORBA. It is our belief that this technology is maturing to the point that it could form the foundations for a sensor architecture that would support the evolutionary development of complex sensor networks.

Sensor-assisted multiple access protocols for wireless networks

Abstract: This paper describes a neural network-based system for stabilizing Aloha random access networks. A grid of sensors is used to gather energy measurements for the neural network. The neural network has been trained to estimate the number of colliding users in a given slot. This information is used to set the parameters of the backoff algorithm so as to stabilize the network. This information can also be used in conjunction with steerable beam antennas to develop geographically-determined Aloha subchannels, further increasing the throughput of the system.