Angela M. Mielke

Radioactive source detection by sensor networks

Detection limits of sensor networks for moving radioactive sources are characterized, using Bayesian methods in conjunction with computer simulation. These studies involve point sources moving at constant velocity, emulating vehicular conveyance on a straight road. For networks involving ten nodes, respective Bayesian methods are implementable in real time. We probe the increased computational requirements incurred by larger numbers of nodes and source trajectory parameters. The complexity appears quadratic in the number of nodes and, also, numerous trajectory parameters may be used. We investigate the consequences of different levels of background radiation. Simulations are shown to be useful for ranking candidate node layouts. We study the detection capabilities of individual sensors and the scalability of detection with sensor density; near the detection limit, increasing the number of sensors can accrue subproportional network sensitivity.

Scalable and Reliable Sensor Network Routing: Performance Study from Field Deployment

Scalable and reliable routing is a critical issue in sensor network deployment. A number of approaches have been proposed for sensor network routing, but sensor field implementation tends to be lacking in the literature. In our study, the problems of scalability and reliability in sensor network routing are addressed through a simple but powerful scheme implemented on Mica2 motes running TinyOS along with other, more widely-used routing protocols. Motes are tested in an outdoor sensor field, and detailed experiments are carried out for performance analysis. This paper presents the implementation details and the results obtained from head-to-head comparison of routing protocols. The proposed protocol delivers 93% of packets injected at a rate of one packet per second in networks with end to end hop distances of over 10 hops-a result which significantly improves upon results from the standard TinyOS routing implementation of MINTRoute. The promising results can be explained by the key protocol properties of reliability (via multi-path redundancy), scalability (with efficiently contained flooding), and flexibility (source-tunable per-packet priority) which are achieved without adding protocol complexity or resource consumption. These strengths enable the protocol to outperform even sophisticated link estimation based protocols especially in adverse outdoor sensor field environments.

Independent sensor networks

The concept of networks of distributed sensors is a popular topic of research. Currently, many systems focus on environmental monitoring applications. Homeland security and the potential for nuclear weapons or dirty bombs has necessitated another type of environmental monitoring, that for radioisotopes. Select traffic points in the United States may be monitored for illicit isotopes by commercially available portal monitoring systems. This article discusses the research efforts at Los Alamos National Laboratory on the development of heterogeneous networks of small, low-power, easily concealed nodes and larger, more compute-capable nodes for in-situ data processing. These networks must be able to reconfigure themselves independently based on the data being collected across a number of sensor types in real time. An application pertinent to current national and global security issues to demonstrate the relevant concepts has been selected. The Los Alamos National Laboratory is developing methods of guarding against a potential terrorist attack using a simple radiological dispersal device (RDD).

Heterogeneous Wireless Sensor Networks

This chapter contains sections titled: Introduction Heterogeneous Wireless Sensor Network Testbeds Scalability and System Lifetime Coverage in Heterogeneous WSNs Management of Heterogeneous WSNs New Applications Enabled by Heterogeneous WSNs Summary of Projects and Systems Infrastructure Open Problems Acknowledgments Bibliography

Kensho: a dynamic tasking architecture for sensor networks

Recent research on sensor network programming architectures has managed to alleviate many common programming burdens, but has not fully addressed the problems associated with tasking and deployment. This has impeded the development of new multi-purpose sensor networks that require new software abstractions and mechanisms. We present the design of a new software architecture for sensor networks that provides abstractions to explicitly address the issues of tasking and deployment. We also present an initial implementation of our architecture in simulation to investigate the potential memory overheads. Finally, we present a mobile tracking application to demonstrate how to use the abstractions provided by our architecture.

Radiation detection and situation management by distributed sensor networks

Detection of radioactive materials in an urban environment usually requires large, portal-monitor-style radiation detectors. However, this may not be a practical solution in many transport scenarios. Alternatively, a distributed sensor network (DSN) could complement portal-style detection of radiological materials through the implementation of arrays of low cost, small heterogeneous sensors with the ability to detect the presence of radioactive materials in a moving vehicle over a specific region. In this paper, we report on the use of a heterogeneous, wireless, distributed sensor network for traffic monitoring in a field demonstration. Through wireless communications, the energy spectra from different radiation detectors are combined to improve the detection confidence. In addition, the DSN exploits other sensor technologies and algorithms to provide additional information about the vehicle, such as its speed, location, class (e.g. car, truck), and license plate number. The sensors are in-situ and data is processed in real-time at each node. Relevant information from each node is sent to a base station computer which is used to assess the movement of radioactive materials.

Chapter 2. Heterogeneous Wireless Sensor Networks

This chapter contains sections titled: Introduction Heterogeneous Wireless Sensor Network Testbeds Scalability and System Lifetime Coverage in Heterogeneous WSNs Management of Heterogeneous WSNs New Applications Enabled by Heterogeneous WSNs Summary of Projects and Systems Infrastructure Open Problems Acknowledgments Bibliography

Development, implementation, and experimentation of parametric routing protocol for sensor networks

The development of a scalable and reliable routing protocol for sensor networks is traced from a theoretical beginning to positive simulation results to the end of verification experiments in large and heavily loaded networks. Design decisions and explanations as well as implementation hurdles are presented to give a complete picture of protocol development. Additional software and hardware is required to accurately test the performance of our protocol in field experiments. In addition, the developed protocol is tested in TinyOS on Mica2 motes against well-established routing protocols frequently used in sensor networks. Our protocol proves to outperform the standard (MINTRoute) and the trivial (Gossip) in a variety of different scenarios.

Continuous monitoring of a capacitor bank

We have developed a prototype system for safety assurance of a capacitor bank by combining application-specific and off-the-shelf surveillance technology for remote monitoring. Traditional surveillance technology passively records facility operations, waiting for an event to trigger a physical audit of the collected information. We have implemented a more active approach to remote monitoring and used the Pulsed Field Laboratory as a test bed. We had various sensors continuously collect information about the state of the laboratory and send it to Guardian, a reasoning system developed at LANL. The detection of an anomalous event begins the recording and analysis of the streams of data from the sensors; the system then presents the results to the laboratory personnel in a Web-based multimedia format for immediate interrogation. This facility provides a unique environment for evaluating, developing, and deploying technology that ensures personnel safety and identifies precursor cues to catastrophic equipment failures.