Showing papers on "Sensor node published in 2001"

Upper bounds on the lifetime of sensor networks

Abstract: We ask a fundamental question concerning the limits of energy efficiency of sensor networks-what is the upper bound on the lifetime of a sensor network that collects data from a specified region using a certain number of energy-constrained nodes? The answer to this question is valuable for two main reasons. First, it allows calibration of real world data-gathering protocols and an understanding of factors that prevent these protocols from approaching fundamental limits. Secondly, the dependence of lifetime on factors like the region of observation, the source behavior within that region, basestation location, number of nodes, radio path loss characteristics, efficiency of node electronics and the energy available on a node, is exposed. This allows architects of sensor networks to focus on factors that have the greatest potential impact on network lifetime. By employing a combination of theory and extensive simulations of constructed networks, we show that in all data gathering scenarios presented, there exist networks which achieve lifetimes equal to or >95% of the derived bounds. Hence, depending on the scenario, our bounds are either tight or near-tight.

A scalable solution to minimum cost forwarding in large sensor networks

Abstract: Wireless sensor networks offer a wide range of challenges to networking research, including unconstrained network scale, limited computing, memory and energy resources, and wireless channel errors. We study the problem of delivering messages from any sensor to an interested client user along the minimum-cost path in a large sensor network. We propose a new cost field based approach to minimum cost forwarding. In the design, we present a novel backoff-based cost field setup algorithm that finds the optimal costs of all nodes to the sink with one single message overhead at each node. Once the field is established, the message, carrying dynamic cost information, flows along the minimum cost path in the cost field. Each intermediate node forwards the message only if it finds itself to be on the optimal path, based on dynamic cost states. Our design does not require an intermediate node to maintain explicit "forwarding path" states. It requires a few simple operations and scales to any network size. We show the correctness and effectiveness of the design by both simulations and analysis.

Scalable Coordination for Wireless Sensor Networks: Self-Configuring Localization Systems

Abstract: Pervasive networks of micro-sensors and actuators offer to revolutionize the ways in which we understand and construct complex physical systems. Sensor networks must be scalable, long-lived and robust systems, overcoming energy limitations and a lack of pre-installed infrastructure. We explore three themes in the design of self-configuring sensor networks: tuning density to trade operational quality against lifetime; using multiple sensor modalities to obtain robust measurements; and exploiting fixed environmental characteristics. We illustrate these themes through the problem of localization, which is a key building block for sensor systems that itself requires coordination.

Energy efficient Modulation and MAC for Asymmetric RF Microsensor Systems

Abstract: Wireless microsensor systems are used in a variety of civil and military applications. Such microsensors are required to operate for years from a small energy source. To minimize the energy dissipation of the sensor node, RF front-end circuitry must be designed based on system level optimization of the entire network. This paper presents several energy minimization techniques derived from the unique properties of a practical short range asymmetric microsensor system. These include energy efficient modulation schemes, appropriate multiple access protocols, and a fast turn-on transmitter architecture.

Distributed sensor networks—a review of recent research

Abstract: Advances in sensor technology and computer networks have enabled distributed sensor networks (DSNs) to evolve from small clusters of large sensors to large swarms of micro-sensors, from fixed sensor nodes to mobile nodes, from wired communications to wireless communications, from static network topology to dynamically changing topology. However, these technological advances have also brought new challenges to processing large amount of data in a bandwidth-limited, power-constraint, unstable and dynamic environment. This paper reviews recent developments in DSNs from four aspects: network structure, data processing paradigm, sensor fusion algorithm with emphasis on fault-tolerant algorithm design, and optimal sensor deployment strategy.

Diagnosis of sensor networks

Abstract: As sensor nodes are embedded into physical environments and becoming integral parts of our daily lives, sensor networks will become the important nerve systems that monitor and actuate our physical environments. We define the process of monitoring the status of a sensor network and figuring out the problematic sensor nodes sensor network diagnosis. However, the high sensor node-to-manager ratio makes it extremely difficult to pay special attention to any individual node. In addition, the response implosion problem, which occurs when a high volume of incoming replies triggered by diagnosis queries cause the central diagnosing node to become a bottleneck, is one major obstacle to be overcome. We describe approaches to addressing the response implosion problem in sensor network diagnosis. We also present simulation experiments on the performance of these approaches, and discuss presentation schemes for diagnostic results.

Internal nodes based broadcasting in wireless networks

Abstract: In a multi-hop wireless network, each node has a transmission radius and is able to send a message to one or all of its neighbors that are located within the radius. In a broadcasting task, a source node sends the same message to all the nodes in the network. Some existing solutions apply re-broadcasting from each cluster-head or border node in a clustered structure. We propose to reduce the communication overhead of the broadcasting algorithm by applying the concept of internal nodes. The maintenance of internal nodes requires much less communication overhead than the maintenance of the cluster structure of the nodes. In one-to-all broadcasting, only the internal nodes forward the message, while in the one-to-one case, messages are forwarded on the edges that connect two internal nodes and on edges that connect each non-internal node with its closest internal node. Existing notions of internal nodes are improved by using node degrees instead of their IDs in internal node decisions. Highest node degrees are also proposed for reducing the number of cluster-heads and border nodes in a clustering algorithm. Further savings are obtained if GPS and the concept of planar subgraphs are used for one-to-one networks. In case of one-to-all model, no re-broadcasting is needed if all neighbors have already received the message. The important features of the proposed algorithms are their reliability, significant savings in the re-broadcasting, and their localized and parameterless behavior. The reduction in the communication overhead for the broadcasting task, with respect to existing methods, is measured experimentally.

Distributed sensor processing over an ad hoc wireless network: simulation framework and performance criteria

Abstract: The evaluation of existing and future distributed sensor processing system concepts can be done well using simulation, provided that the simulation is faithful in representing both the medium in which the sensors interface with the phenomena that they measure or detect and the medium in which the sensors interface with each other to achieve a distributed mode of operation. Performance criteria for distributed sensor processing over ad hoc wireless networks are stated and an architecture for analysis and simulation of this kind of system is described.

System and method for communicating optical signals between a data service provider and subscribers

Abstract: An optical fiber network can include an outdoor laser transceiver node that can be positioned in close proximity to the subscribers of an optical fiber network. The outdoor laser transceiver node does not require active cooling and heating devices that control the temperature surrounding the laser transceiver node. The laser transceiver node can adjust a subscriber's bandwidth on a subscription basis or on an as-needed basis. The laser transceiver node can also offer data bandwidth to the subscriber in preassigned increments. Additionally, the laser transceiver node lends itself to efficient upgrading that can be performed entirely on the network side. The laser transceiver node can also provide high speed symmetrical data transmission. Further, the laser transceiver node can utilize off-the-shelf hardware to generate optical signals such as Fabry-Perot (F-P) laser transmitters, distributed feed back lasers (DFB), or vertical cavity surface emitting lasers (VCSELs).

Architecture strategies for energy-efficient packet forwarding in wireless sensor networks

Abstract: The energy-efficient communication among wireless sensor nodes determines the lifetime of a sensor network and exhibits patterns highly dependable on the sensor application and networking software. This software is responsible for processing the sensor data and disseminating the data to other nodes or a central repository. In this paper we propose a node architecture that takes advantage of both the intelligence of the radio hardware and the needs of applications to efficiently handle the packet forwarding. It exploits principles widely used in modem firewall network architectures and as our analysis shows achieves considerable energy savings.

Operating system and algorithmic techniques for energy scalable wireless sensor networks

Abstract: An system-level power management technique for massively distributed wireless microsensor networks is proposed. A power aware sensor node model is introduced which enables the embedded operating system to make transitions to different sleep states based on observed event statistics. The adaptive shutdown policy is based on a stochastic analysis and renders desired energy-quality scalability at the cost of latency and missed events. The notion of algorithmic transformations that improve the energy quality scalability of the data gathering network are also analyzed.

System and method for efficiently performing two-way ranging to determine the location of a wireless node in a communications network

Abstract: A system and method for reducing the number of transmissions required for a node in a communications network to range other nodes in the network, while also enabling the node to continuously monitor the reservation channel during the ranging process without the use of a second receiver, and to indicate to the ranged node and other nodes in the network that the ranging node and the ranged node are not tuning to a data channel to perform the ranging, to thus enable the node to more efficiently determine its geographic location. The system and method further enables a node in a wireless communications network to minimize the amount of time it is not monitoring the reservation channel while receiving information messages from other nodes in the network.

Operating System and Algorithmic Techniques for Energy Scalable Wireless Sensor Networks

Abstract: An system-level power management technique for massively distributed wireless microsensor networks is proposed A power aware sensor node model is introduced which enables the embedded operating system to make transitions to different sleep states based on observed event statistics The adaptive shutdown policy is based on a stochastic analysis and renders desired energy-quality scalability at the cost of latency and missed events The notion of algorithmic transformations that improve the energy quality scalability of the data gathering network are also analyzed

Cover Me! A Self-Deployment Algorithm for Mobile Sensor Networks

Abstract: This paper describes an algorithm for deploying a mobile sensor network. A mobile sensor network is made up of a distributed collection of nodes, each of which has sensing, computation, communication and locomotion capabilities. In this paper, we describe an incremental deployment algorithm in which nodes are deployed one-at-a-time into an unknown environment. Each node makes use of information gathered by previously deployed nodes to determine its optimal deployment location. The algorithm is designed to maximize network ‘coverage’ whilst ensuring that nodes retain line-of-sight with one another (this latter constraint arises from the need to localize the nodes: in our previous work on mesh-based localization [9], [10] we have shown how nodes can localize themselves in a completely unknown environment by using other nodes as landmarks). In this paper, we describe a series of experiments (conducted in both simulation and reality) aimed at validating the algorithm and illuminating its empirical properties.

System and method for computing the signal propagation time and the clock correction for mobile stations in a wireless network

Abstract: A system and method for enabling a node, such as a mobile user terminal in a wireless communications network, such as an ad-hoc network, to effectively and efficiently determine a clock correction factor for its local clock relative to a local clock of at least one other node The node calculates a difference between the timing of the local clock of the node and the local clock of the other node based on the timing of signals transmitted between the node and the other node, and information pertaining to the transmission and reception of these signals by the node and the other node as indicated by the respective local clocks of the node and the other node The system and method further enables a plurality of nodes in an ad-hoc packet-switched communications network to calculate their respective local clock correction factors relative to the local clocks of their neighboring nodes in this manner with minimal message transmissions between the nodes, to reduce the amount of overhead in the network needed for such clock correcting operations

Optical transceiver design and mechanical features

Abstract: A node for use in a wireless communication network that facilitates alignment of the node with other nodes in the network and a method for aligning the node. The node includes mounting fixtures that enables the mounting of GPS receivers and a tiltmeter to obtain position and bearing information for the node. The node contains alignment features that enable the positioning of an optical transmitter/receiver pair in the node using the data obtained from the GPS receivers and tiltmeter.

Fundamental protocols for wireless sensor networks

Abstract: The main contribution of this work is to present energyefficient protocols that compute the sum of n numbers over any commutative and associative binary operator stored in n wireless sensor nodes arranged in a two-dimensional grid of size √ n × √ n. We first present a protocol that computes the sum in O(r 2 +( n r2) 1 3) time slots with no sensor node being awake for more than O(1) time slots, where r is the transmission range of the sensor nodes. We then show a fault-tolerant protocol that computes the sum in the same number of time slots with no sensor node being awake for more than O(log r) time slots.

System and method for determining the measure of mobility of a subscriber device in an ad-hoc wireless network with fixed wireless routers and wide area network (WAN) access points

Abstract: A system and method for determining the mobility of a node in a network, such as a wireless ad-hoc network that requires the node to share its information with other mobile and stationary nodes, such as fixed wireless routers and intelligent access points, so that the rate at which the node shares this information and receives location information, such as Geo-location updates, could be based on the rate of mobility of the node. The node includes a transceiver which is adapted to communicate or attempt to communicate with at least one of the stationary other nodes in the network, and a controller which is adapted to determine a mobility factor of the node based on the communication or attempted communication with the at least one stationary other node. The controller is further adapted to control a rate at which the transceiver sends information pertaining to the node to at least one of the other nodes in the network based on the mobility factor. The mobility factor represents a rate of mobility of the node, and the rate at which the controller controls the transceiver to send the information is proportional to the rate of mobility.

Interface system for wireless node and network node

Abstract: An interface between a wireless node and a network node includes an encapsulator for temporarily converting data frames into Ethernet frames for the link between the two nodes and de-encapsulating the Ethernet frames before the data is processed at the network node.

Correlative signal processing in wireless SAW sensor applications to provide multiple-access capability

Abstract: We present a new method of evaluating the information of interest in the output response of surface acoustic wave (SAW) sensors. A well-known spread-spectrum technique is used to get the sensor information from an individually addressed SAW sensor. On-off keying-coded SAW sensors are picked out of a number of sensors by correlating the sensor response signal with a replica of the known response signal of a particular sensor. The influence of a measurement quantity (e.g., temperature, pressure, current, voltage,...) on a SAW sensor can be observed as a scaling of time and shape of the sensor response signal. This scaling factor is evaluated by use of correlative signal processing techniques. A main advantage of this method is the capability of multiple access, i.e., to distinguish different sensors in the range of a single interrogation system. Since this technique makes it possible to deal with sensor response signals overlapping in the time domain, sensors can remain short and, therefore, cheap. The principle of operation, limits of the method, and experimental results for temperature measurements are also presented.

Large-scale Network Discovery: Design Tradeoffs in Wireless Sensor Systems

Abstract: We are investigating design tradeoffs relating to the structure of the network formed in large-scale selforganizing wireless sensor systems. In such systems, most traffic is in the form of many-to-one data flows, between all the networked sensors and a central monitoring node. We refer to the process of establishing a multi-hop routing path from every sensor node in the system to the monitoring node as Network Discovery. Flooding, which is conventionally used for disseminating information, can also be used for network discovery. The central monitoring node initiates the flooding by forwarding a message to all its neighbors, each successive node forwarding it once. As the flooding proceeds, nodes keep track of who they received messages from. If a given node receives multiple copies of the flooding message from different neighboring senders, it may use a parent-selection mechanism to choose one of these as its parent. The nodes then send information to their parent, along along the reverse direction of the original flooding message, when they need to forward any data back to the monitoring node. The network topology that is thus discovered is a spanning tree. It is of interest to know whether the discovered routing tree is bushy, with a few large clusters, or sparse, with many smaller clusters. Three factors affecting the structure of the discovered routing tree are the flooding mechanism, the transmission power, and the parent selection algorithm. The bushiness of the discovered tree structure will have direct implications in terms of application data aggregation, energy utilization, system throughput and robustness. We would like to address a number of related questions in our investigations. What are the tradeoffs among these implications? Increasing the radio transmission power decreases the degree of spatial reuse in the network, but results in a bushier tree structure where greater application data aggregation can occur. How does this change the overall system throughput? Bushy trees also result in highly non-uniform energy utilization as opposed to sparse trees; but do they utilize less energy overall? How robust are bushy trees to different kinds of node failures? Finally, how can the use of different parent selection mechanisms help in controlling the bushiness of the discovered tree? Our initial results in this study are obtained from a combination of theoretical models and empirical data from prototype wireless sensor networks consisting of over 150 nodes. These results suggest that when the transmission radius of nodes is large, and basic flooding with a simple parent-selection mechanism is used, the topology of the discovered routing tree is in fact bushy and follows a power law distribution. Most nodes are leaf nodes, and a small-yet-significant number of the nodes are cluster-heads with a large number of children. This happens because , in a given area, the first node which wins the medium-access contention and broadcasts the flood message first becomes the parent of all new receivers. This “winner gets all” scenario is

Video semaphore decoding for free-space optical communication

Abstract: Using teal-time image processing we have demonstrated a low bit-rate free-space optical communication system at a range of more than 20km with an average optical transmission power of less than 2mW. The transmitter is an autonomous one cubic inch microprocessor-controlled sensor node with a laser diode output. The receiver is a standard CCD camera with a 1-inch aperture lens, and both hardware and software implementations of the video semaphore decoding algorithm. With this system sensor data can be reliably transmitted 21 km form San Francisco to Berkeley.

Adaptive power control for wireless networks

Abstract: Power control techniques in wireless network for reducing mobile nodes' power consumption and achieving lower signal-to-interference ratio are disclosed. The proposed power control scheme for distributed networks discloses a method for adapting and storing the power level for transmission between the nodes. For each node that communicates with other nodes in the network the power level is calculated and stored in the node's memory (power cache). Each node continuously builds up its power cache. The calculation of the required transmission power level is done either at the receiving node or at the transmitting node. The resulting calculated power level is stored at the transmitting node for reference and for use in future transmissions.

Multiple access bandwidth-on-demand using MSPK with an embedded tracking channel

Abstract: A communications system comprising a central node, at least one remote node and a communications link. The remote node is adapted to receive information transmitted from the central node over a broadcast link and the communications link is adapted to convey information from the remote node to the central node. The central node is adapted to dynamically tailor a remote node transmit power control and a bandwidth as requested by the remote node for conveying information over the communications link.

An energy-efficient initialization protocol for wireless sensor networks

Abstract: A wireless sensor network (WSN, for short) is a distributed system consisting of n sensor nodes and a base station. We propose an energy-efficient protocol to initialize sensor nodes in WSNs, that is, to assign a unique ID to each sensor node. We show that if the number n of sensor nodes is known beforehand, for any f/spl ges/1 and any small /spl mu/ (O

On the Limits and Applications of MEMS Sensor Networks

Abstract: Wireless sensor nodes will become inexpensive and common over the next decade. Some of the physical limits to the underlying technology are discussed. Predictions of future performance are made. Three militarily relevant applications examples are given.

Cmos imager frame capture

Abstract: A CMOS imager capable of operating in a frame capture mode. The imager has an array of active pixel sensors (APS) which sense and store incident light levels at discrete points in the array and a shutter for determining the period of time that light is incident on the array. The shutter, such as a controlled liquid crystal, may be positioned on the array surface or some distance from it, allowing incident light to pass through the shutter and impinge on the array, or the shutter may be positioned at an oblique angle to the array to reflect incident light onto the array. When the APS's in the array are 4T or 5T APS's with a sensor node and a storage node, the two nodes may be connected through two or more series connected transistors or a long transistor to prevent sub-threshold currents. Also, the storage node may be connected to the gate of a feedback transistor to raise the voltage on the storage node as the voltage on the storage node degrades.

Method and system for channel count and power control in optical networks

Abstract: There is proposed a technique for counting channels at a node of a multi-channel optical network, where the node is connected to a following node and a preceding node by an optical communication line carrying a plurality of information optical channels. The technique comprises exchanging of information structures between the nodes, such that each of the information structures specifies particular optical information channels which are currently in use at a predetermined network section or node.