Showing papers on "Wireless sensor network published in 2000"

Energy-efficient communication protocol for wireless microsensor networks

Abstract: Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.

Energy-efficient communication protocols for wireless microsensor networks

Abstract: Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have signicant impact on the overall energy dissipation of these networks. Based on our ndings that the conventional protocols of direct transmission, minimum-transmission-energy, multihop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster base stations (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show that LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional routing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated.

Directed diffusion: a scalable and robust communication paradigm for sensor networks

Abstract: Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network.

GPS-less low-cost outdoor localization for very small devices

Abstract: Instrumenting the physical world through large networks of wireless sensor nodes, particularly for applications like environmental monitoring of water and soil, requires that these nodes be very small, lightweight, untethered, and unobtrusive. The problem of localization, that is, determining where a given node is physically located in a network, is a challenging one, and yet extremely crucial for many of these applications. Practical considerations such as the small size, form factor, cost and power constraints of nodes preclude the reliance on GPS of all nodes in these networks. We review localization techniques and evaluate the effectiveness of a very simple connectivity metric method for localization in outdoor environments that makes use of the inherent RF communications capabilities of these devices. A fixed number of reference points in the network with overlapping regions of coverage transmit periodic beacon signals. Nodes use a simple connectivity metric, which is more robust to environmental vagaries, to infer proximity to a given subset of these reference points. Nodes localize themselves to the centroid of their proximate reference points. The accuracy of localization is then dependent on the separation distance between two-adjacent reference points and the transmission range of these reference points. Initial experimental results show that the accuracy for 90 percent of our data points is within one-third of the separation distance. However, future work is needed to extend the technique to more cluttered environments.

Protocols for self-organization of a wireless sensor network

Abstract: We present a suite of algorithms for self-organization of wireless sensor networks in which there is a scalably large number of mainly static nodes with highly constrained energy resources. The protocols further support slow mobility by a subset of the nodes, energy-efficient routing, and formation of ad hoc subnetworks for carrying out cooperative signal processing functions among a set of the nodes.

PicoRadio supports ad hoc ultra-low power wireless networking

Abstract: Technology advances have made it conceivable to build and deploy dense wireless networks of heterogeneous nodes collecting and disseminating wide ranges of environmental data. Applications of such sensor and monitoring networks include smart homes equipped with security, identification, and personalization systems; intelligent assembly systems; warehouse inventory control; interactive learning toys; and disaster mitigation. The opportunities emerging from this technology give rise to new definitions of distributed computing and the user interface. Crucial to the success of these ubiquitous networks is the availability of small, lightweight, low-cost network elements, which the authors call PicoNodes. The authors present a configurable architecture that enables these opportunities to be efficiently realized in silicon. They believe that this energy-conscious system design and implementation methodology will lead to radio nodes that are two orders of magnitude more efficient than existing solutions.

Constraints and approaches for distributed sensor network security

Abstract: Executive Summary Confidentiality, integrity, and authentication services are critical to preventing an adversary from compromising the security of a distributed sensor network. Key management is likewise critical to establishing the keys necessary to provide this protection. However, providing key management is difficult due to the ad hoc nature, intermittent connectivity, and resource limitations of the sensor network environment. As part of the SensIT program, NAI Labs is addressing this problem by identifying and developing cryptographic protocols and mechanisms that efficiently provide key management security support services. This document describes our sensor network constraints and key management approaches research for FY 2000. As a first step, NAI Labs has researched battlefield sensor and sensor network technology and the unique communications environment in which it will be deployed. We have identified the requirements specific to our problem of providing key management for confidentiality and group-level authentication. We have also identified constraints, particularly energy consumption, that render this problem difficult. NAI Labs has developed novel key management protocols specifically designed for the distributed sensor network environment, including Identity-Based Symmetric Keying and Rich Uncle. We have analyzed both existing and NAI Labs-developed keying protocols for their suitability at satisfying identified requirements while overcoming battlefield energy constraints. Our research has focused heavily on key management energy consumption, evaluating protocols based on total system, average sensor node, and individual sensor node energy consumption. We examined a number of secret-key-based protocols, determining some to be suitable for sensor networks but all of the protocols have flexibility limitations. Secret-key-based protocols are generally energy-efficient, using encryption and hashing algorithms that consume relatively little energy. Security of secret-key-based protocols is generally determined by the granularity of established keys, which vary widely for the protocols described herein. During our examination of these protocols we noted that some of these protocols are not sufficiently flexible for use in battlefield sensor network, since they cannot efficiently handle unanticipated additions of sensor nodes to the network. Our Identity-Based Symmetric Keying protocol and the less efficient Symmetric Key Certificate Based Protocol are well suited for certain sensor networks, establishing granular keys while consuming relatively little energy. However, all of the secure secret-key-based protocols use special nodes that operate as Key Distribution Centers (or Translators). The sensor nodes communicate with these centers exchanging information as part of the key establishment process. Since these special nodes are expected to make up less than 1% of the sensor …

Wireless medium access control protocols

Abstract: Technological advances, coupled with the flexibility and mobility of wireless systems, are the driving force behind the Anyone, Anywhere, Anytime paradigm of networking. At the same time, we see a convergence of the telephone, cable and data networks into a unified network that supports multimedia and real-time applications like voice and video in addition to data. Medium access control protocols define rules for orderly access to the shared medium and play a crucial role in the efficient and fair sharing of scarce wireless bandwidth. The nature of the wireless channel brings new issues like location-dependent carrier sensing, time varying channel and burst errors. Low power requirements and half duplex operation of the wireless systems add to the challenge. Wireless MAC protocols have been heavily researched and a plethora of protocols have been proposed. Protocols have been devised for different types of architectures, different applications and different media. This survey discusses the challenges in the design of wireless MAC protocols, classifies them based on architecture and mode of operation, and describes their relative performance and application domains in which they are best deployed.

SensorSim: a simulation framework for sensor networks

Abstract: The advent of wireless micro sensors promises many yet unrealized benefits. A network of such sensors or “sensor network” introduces a new set of challenges. Besides being able to communicate effectively, sensor networks have demanding sensing tasks. First, they must be aware of their environment and oftentimes are required to adapt to their surroundings. Second, they must coordinate among them to perform a greater group-sensing task. In this context, the study of sensor networks has numerous other aspects besides communication. To create a better understanding of sensor networks and to facilitate the development of new protocols and applications, detailed simulation and performance evaluation techniques need to be developed. In this paper, we introduce our ongoing efforts in the development of SensorSim, a simulation framework that introduces new models and techniques for the design and analysis of sensor networks. SensorSim inherits the core features of traditional event driven network simulators, and builds up new features that include ability to model power usage in sensor nodes, hybrid simulation that allows the interaction of real and simulated nodes, new communication protocols and real time user interaction with graphical data display. After discussing the details of SensorSim, we provide our current results, that demonstrate various capabilities of SensorSim.

An integrated architecture for cooperative sensing networks

Abstract: Distributed sensor networks (DSNs) consisting of many small, low-cost, spatially dispersed, communicating nodes have been proposed for many applications, such as area surveillance and environmental monitoring. Trends in integrated electronics, such as better performance-to-cost ratios, low-power radios, and microelectromechanical systems (MEMS) sensors, now allow the construction of sensor nodes with signal processing, wireless communications, power sources and synchronization, all packaged into inexpensive miniature devices. If these devices can be easily deployed and self-integrated into a system, they promise great benefits in providing real-time information about environmental conditions. Intelligent sensor nodes function much like individual ants that, when formed into a network, cooperatively accomplish complex tasks and provide capabilities greater than the sum of the individual parts. The paper discusses several technical challenges that must be overcome to fully realize the viability of the DSN concept in realistic application scenarios.

An architecture for building self-configurable systems

Abstract: Developing wireless sensor networks can enable information gathering, information processing and reliable monitoring of a variety of environments for both civil and military applications. It is however necessary to agree upon a basic architecture for building sensor network applications. This paper presents a general classification of sensor network applications based on their network configurations and discusses some of their architectural requirements. We propose a generic architecture for a specific subclass of sensor applications which we define as self-configurable systems where a large number of sensors coordinate amongst themselves to achieve a large sensing task. Throughout this paper we assume a certain subset of the sensors to be immobile. This paper lists the general architectural and infra-structural components necessary for building this class of sensor applications. Given the various architectural components, we present an algorithm that self-organizes the sensors into a network in a transparent manner. Some of the basic goals of our algorithm include minimizing power utilization, localizing operations and tolerating node and link failures.

Energy-scalable algorithms and protocols for wireless microsensor networks

Abstract: Wireless microsensor networks lend themselves to trade-offs in energy and quality. In these networks, the individual sensor data per se are not necessarily important to the end user. Rather, it is the combined knowledge of all the sensors that describes what is occurring in the environment. By allowing the algorithms and protocols to adapt the quality of this description, with a corresponding change in energy dissipation, sensor networks can be flexible to the end-user's requirements. In this paper, we provide models for predicting quality and energy and show the advantages of trading off these two parameters. By ensuring that the system operates at a minimum energy for each quality point, the system can achieve both flexibility and energy efficiency, allowing the end-user to maximize system lifetime.

Power-conscious design of wireless circuits and systems

Abstract: The great importance of power consciousness is well understood in mobile wireless communications. However, with growing experience the fundamental principles underlying power conscious design of RF circuits, systems, and networks are only now becoming known. Using as example ultralow-power wireless devices for messaging such as paging receivers and wireless sensor networks, the first part of this paper presents the relationship between current consumption and dynamic range of low-noise amplifiers, mixers, oscillators, and active filters. The second part of the paper covers issues of modulation, protocols, and networking that would be required in dense networks of wireless sensors, which communicate using very little energy. These ideas are expected to find use in most forms of digital wireless communications.

Optimal design of fault tolerant sensor networks

Abstract: The selection of measurements is one of the most important problems in the design of process instrumentation. This paper deals with the design of sensor networks such that the observability of the variables, which are necessary for the process control, remains satisfied in the presence of sensor failures. Pseudo-minimal and minimal sensor sets are organized into an oriented graph which contains all the possible reconfiguration paths for which those variables remain observable. A bottom-up analysis of this graph allows one to compute reliability functions which evaluate the robustness of the observability property with respect to sensor failures. The design of optimal sensor networks thus resumes to finding pseudo-minimal sensor sets such that the mean time before losing the observability property is larger than a pre-defined value.

PicoRadio: Ad-hoc wireless networking of ubiquitous low-energy sensor/monitor nodes

Abstract: One of the most compelling challenges of the next decade is the solution of the "last meter" problem, which extends the network into the end-user data-collection and monitoring devices. This paper discusses the challenges and opportunities of a "PicoRadio Network" that supports the assembly of an an-hoc wireless network of meso-scale, low-cost and low-energy sensor and monitor nodes.

Utility-based decision-making in wireless sensor networks

Abstract: We consider challenges associated with application domains in which a large number of distributed, networked sensors must perform a sensing task repeatedly over time. We address issues such as resource constraints, utility associated with a sensing task, and achieving global objectives with only local information. We present a model for such applications, in which we define appropriate global objectives based on utility functions and specify a cost model for energy consumption. In the full version of this paper, we present algorithms and experimental results for this problem domain [2].

Sensor Information Networking Architecture

Abstract: The advent of technology has facilitated the development of networked systems of extremely small, low-power devices that combine programmable general-purpose computing with multiple sensing and wireless communication capability. This networked system of programmable sensor nodes, which together form a sensor network, poses unique challenges on how information collected by, and stored within, the sensor network could be queried and accessed, and how concurrent sensing tasks could be executed internally and programmed by external users. In this paper, we describe SINA (Sensor Information Networking Architecture), which facilitates the querying, monitoring and tasking of sensor networks. We model a sensor network as a collection of massively distributed objects, and SINA plays the role of middleware that facilitates the adaptive organization of sensor information. The SINA kernel provides a set of configuration and communication primitives that enable the scalable, robust and energy-efficient organization of, and interactions among, sensor objects. On top of the SINA kernel is a programmable substrate that follows the spreadsheet paradigm and provides mechanisms to create associations among sensor nodes. Users then access information within a sensor network using declarative queries and perform tasks using programmable scripts. Issues concerning interworking between stationary sensor networks and mobile nodes are also addressed.

A Wireless Sensor Network for Smart Roadbeds and Intelligent Transportation Systems

Abstract: We have developed a wireless sensor package to instrument roadways for Intelligent Transportation Systems. The sensor package counts passing vehicles, measures the average roadway speed, and detects ice and water on the road. Clusters of sensors can transmit this information in near real-time to wired base stations for use controlling and predicting traffic, and in clearing road hazards. The sensor package draws a maximum time-averaged current of 17 tA from an internal lithium battery, allowing it to operate in the roadbed for at least 10 years without maintenance. The nodes cost well under $30 to manufacture, and can be installed without running wires under the road, facilitating wide deployment. Unlike many other types of traffic sensors, these sensors count vehicles in bumper-to-bumper traffic just as well as in widely separated traffic. The devices detect vehicles by detecting the perturbations in the Earth's magnetic field caused by the vehicles. They measure this perturbation using an anisotropic magnetoresistive magnetic field sensor. The radio transmitters in the sensor are frequency-agile, and the sensors use a randomized sparse TDMA protocol, which allows several transmit-only devices to share a channel. The sensor package includes a custom-designed, compact, broadband, inexpensive printed circuit microstrip antenna for the 915 MHz U.S. ISM band. We built a prototype sensor package, and installed it in a pothole in a city street. We used the sensor to monitor the traffic flow rate during free-flowing traffic and a traffic jam. Thesis Supervisor: Joseph Paradiso Title: Principal Research Scientist, MIT Media Lab

Random access MAC for efficient broadcast support in ad hoc networks

Abstract: Wireless communications are becoming an important part of our everyday lifestyle. One major area that will have an enormous impact on the performance of wireless ad hoc networks is the medium access control (MAC) layer. Current random access MAC protocols for ad hoc networks support reliable unicast but not reliable broadcast. We propose a random access MAC protocol, broadcast support multiple access (BSMA), which improves the broadcast reliability in ad hoc networks.

The mobile patient: wireless distributed sensor networks for patient monitoring and care

Abstract: The concept of a three layer distributed sensor network for patient monitoring and care is introduced. The envisioned network has a leaf node layer (consisting of patient sensors), an intermediate node layer (consisting of the supervisory processor residing with each patient) and the root node processor (residing at a central monitoring facility). The paradigm has the capability of dealing with the bandwidth bottleneck at the wireless patient-root node link and the processing bottleneck at the central processor or root node of the network.

Managing context data for smart spaces

Abstract: Describes our on-going efforts to construct a service infrastructure to support smart environments. We characterize "fusion services", which extract and infer useful context information from sensor data, using evidential reasoning techniques. We specify sensing services as Bayesian networks and use information-theoretic algorithms to optimize the resources consumed by the rendering of a service. We define a "quality-of-information" metric to characterize sensing service performance. We have implemented an infrastructure for supporting a dynamic set of sensors and services in a smart space. Using this infrastructure and an IEEE 802.11 network, we implemented a probabilistic indoor location system that optimizes the number of sensors consulted when determining the location of a user while maintaining a high degree of accuracy.

Sensor Web for in situ exploration of gaseous biosignatures

Abstract: A Sensor Web is a system of intra-communicating spatially distributed sensor pods that can be deployed to monitor and explore new environments. By its very nature, the Sensor Web provides spatio-temporal data in a form consistent with that needed for environment modeling and represents a new paradigm for in situ monitoring and exploration. For example, a wireless web of scattered sensor pods on the Martian surface is an ideal way to pursue gaseous biosignature searches. Sensor Web climate and agricultural monitoring on Earth (particularly when coupled with remote measurements) characterize significant commercial opportunities for this technology. Recent laboratory demonstrations at the Jet Propulsion Laboratory (JPL) have shown the potential of current Sensor Web technology, These demonstrations are leading to a JPL effort to field a Sensor Web in Baja California to examine gaseous biosignatures from the microbial mats there.

Design of Sensor Network Based on the Signed Directed Graph of the Process for Efficient Fault Diagnosis

Abstract: An optimally located network of sensors is a prerequisite for successful application of fault diagnosis techniques. Most of the previous work in the area of fault diagnosis deals with methodologies for identifying possible faults, given sensor data. Available literature suggests that very little work has been done on methods for optimally locating the sensors for efficient fault diagnosis. Some algorithms based on the concepts of observability and resolution were discussed in our previous work (ref 1: Raghuraj et al. AIChE J. 1999, 45 (2), 310). These algorithms are based on a digraph (DG) representation of the process. In this article, the sensor location work is extended to use the signed directed graph (SDG) representation of the process. Various issues involved in utilizing the SDG of the process for the problem of sensor location are discussed. Algorithms for sensor network design based on the SDG of the process are detailed and applied to two chemical engineering case studies. It is shown that bett...

Wireless personal area networks in telemedical environment

Abstract: Presents a new design of a wireless personal area network with physiological sensors for medical applications in a telemedical environment. Intelligent wireless sensors perform data acquisition and limited processing. Individual sensors monitor specific physiological signals (such as EEG, EGG, GSR, etc.) and communicate with each other and the personal server. The personal server integrates information from different sensors and communicates with the rest of the telemedical system as a standard mobile unit. The authors present their prototype implementation of the wireless intelligent sensor (WISE) based on a very low power consumption microcontroller and a DSP-based personal server. In future the authors expect all components of WISE to be integrated in a single chip for use in a variety of new medical applications and sophisticated human computer interfaces.

Wireless integrated network sensors (WINS): distributed in situ sensing for mission and flight systems

Abstract: Wireless Integrated Network Sensors (WINS) form a new distributed information technology of combined sensor, actuator, and processing systems. WINS distributed nodes form autonomous, self-organized, wireless sensing and control networks. WINS nodes include microsensors, signal processing, computation and low power wireless networking. WINS enable distributed measurements for applications ranging from aerospace system condition monitoring to distributed environmental science monitoring. This paper will discuss the enabling technology advances of WINS for mission and flight system in situ sensing. This will include the complete set of technologies, from new MEMS devices through information technology. Finally, a new WINS generation, GlobalWINS, will be described. GlobalWINS has been developed for planetary-wide distribution of science instruments.

A wireless pressure-measurement system using a SAW hybrid sensor

Abstract: A pressure-measurement system based on surface-acoustic-wave (SAW) sensors is presented in this paper. Since SAW sensors are powered by the energy of the RF field, no battery is required, which is a major drawback of conventional microcontroller-based telemetry systems. A successful combination of a SAW reflective delay line with a high-Q capacitive pressure sensor is shown, With a new way of matching the sensor impedance to the SAW reflector impedance, both a high signal-to-noise ratio and a high signal dynamic are achieved, which supports accurate signal evaluation. As an example of realization, the prototype of the pressure sensor unit is presented.

A low-power low-voltage transceiver architecture suitable for wireless distributed sensors network

Abstract: A broad range of new high-volume consumer applications require the availability of low-power, battery operated, wireless microsystems. These systems should conciliate a sufficient battery lifetime with reduced overall dimensions (including antenna), low cost and versatility. The design of such systems highlights many tradeoffs between performances, cost and power consumption. These considerations led our group to choose a direct-conversion scheme for a distributed sensors application. The key blocks for this architecture have been realized and measured in a 0.5 /spl mu/m CMOS technology, validating this approach. From these results, the total power consumption of a receiver operating in the 433 MHz ISM band is expected as low as 1.4 mW, under 1.2 V supply, for a sensitivity of -100 dBm and a 20 kbit/s data rate. The transmitter provides 9 dBm output power under the same supply voltage, with a 35% efficiency.

Querying and tasking in sensor networks

Abstract: With the advancement of hardware technology, it becomes feasible to develop a networked system of pervasive computing platforms that combine programmable general purpose computers with multiple sensing and wireless communication capability. This networked system of programmable sensor nodes, together called a sensor network, poses unique challenges on how information collected by and stored within the sensor network should be queried and accessed, and how concurrent sensing tasks should be programmed from external clients. In this paper, we describe an architecture that facilitates querying and tasking of sensor networks. The key idea to the architecture lies in the development of the Sensor Querying and Tasking Language (SQTL) and the corresponding Sensor Execution Environment (SEE). We model a sensor network as a distributed set of collaborating nodes that carry out querying and tasking activities programmed in SQTL. A frontend node injects a message, that encapsulates an SQTL program, into a sensor node and starts a diffusion computation. A sensor node may diffuse the encapsulated SQTL program to other nodes as dictated by its logic and collaborately perform the specified querying or tasking activity. We will present the SQTL language and demonstrate its applicability using a maximum temperature querying application and a vehicle tracking application.