Anthony D. Wood

For a more compact list of publications, as well as research interests and other information, please see my curriculum vitae.

Journals

Context-Aware Wireless Sensor Networks for Assisted-Living and Residential Monitoring

Citation:

A. Wood, J. Stankovic, G. Virone, L. Selavo, Z. He, Q. Cao, T. Doan, Y. Wu, L. Fang, R. Stoleru, “Context-Aware Wireless Sensor Networks for Assisted-Living and Residential Monitoring,” IEEE Network, 22(4):26–33, July–August 2008.

Summary:

Improving the quality of healthcare and the prospects of “aging in place” using wireless sensor technology requires solving difficult problems in scale, energy management, data access, security, and privacy. We present AlarmNet, a novel system for assisted-living and residential monitoring that uses a two-way flow of data and analysis between the front and back-ends to enable context-aware protocols that are tailored to residents' individual patterns of living.

AlarmNet integrates environmental, physiological, and activity sensors in a scalable, heterogeneous architecture. The SenQ query protocol provides real-time access to data and lightweight in-network processing. Circadian Activity Rhythm (CAR) analysis learns resident activity patterns and feeds them back into the network to aid context-aware power management and dynamic privacy policies.

Formats:

PDF

Denial of Service in Sensor Networks

Citation:

Anthony Wood, John A. Stankovic, “Denial of Service in Sensor Networks,” IEEE Computer, 35(10):54-62, October 2002.

Summary:

Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments. Their foreseeable applications will help protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources.

In these and other vital or security-sensitive deployments, keeping the network available for its intended use is essential. The stakes are high: Denial-of-service (DoS) attacks against such networks may permit real-world damage to the health and safety of people. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult.

To identify DoS vulnerabilities, we analyze two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment.

Formats:

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Refereed Proceedings

Online Coding for Reliable Data Transfer in Lossy Wireless Sensor Networks

Citation:

Anthony D. Wood and John A. Stankovic, “Online Coding for Reliable Data Transfer in Lossy Wireless Sensor Networks,” in The 5th IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS '09), Marina Del Rey, CA, June 2009.

Summary:

Bulk transport underlies data exfiltration and code update facilities in WSNs, but existing approaches are not designed for highly lossy and variable-quality links. We observe that Maymounkov's rateless online codes are asymptotically more efficient, but can perform poorly in the WSN operating region. We analyze and optimize coding parameters and present the design and evaluation of RTOC, a protocol for bulk transport that recovered over 95% of application data despite up to 84% packet loss in a MicaZ network.

Formats:

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SenQ: An Embedded Query System for Streaming Data in Heterogeneous Interactive Wireless Sensor Networks

Citation:

Anthony D. Wood, Leo Selavo, John A. Stankovic, “SenQ: An Embedded Query System for Streaming Data in Heterogeneous Interactive Wireless Sensor Networks,” in The 4th IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS), Santorini Island, Greece, June 2008. (short paper)

Summary:

Interactive wireless sensor networks (IWSNs) manifest diverse application architectures, hardware capabilities, and user interactions that challenge existing centralized or VM-based query system designs. To support in-network processing of streaming sensor data in such heterogeneous environments, we created SenQ, a multi-layer embedded query system. SenQ enables user-driven and peer-to-peer in-network query issue by wearable interfaces and other resource-constrained devices. Complex virtual sensors and user-created streams can be dynamically discovered and shared, and SenQ is extensible to new sensors and processing algorithms. We evaluated SenQ's efficiency and performance in a testbed for assisted-living, and show that on-demand buffering, query caching, efficient restart and other optimizations reduce network overhead and minimize data latency.

Formats:

PDF

LUSTER: Wireless Sensor Network for Environmental Research

Citation:

L. Selavo, A. Wood, Q. Cao, T. Sookoor, H. Liu, A. Srinivasan, Y. Wu, W. Kang, J. Stankovic, D. Young, J. Porter, “LUSTER: Wireless Sensor Network for Environmental Research,” in The 5th ACM Conference on Embedded Networked Sensor Systems (SenSys), Sydney, Australia, Nov. 2007.

Summary:

Environmental wireless sensor network (EWSN) systems are deployed in potentially harsh and remote environments where inevitable node and communication failures must be tolerated. LUSTER—Light Under Shrub Thicket for Environmental Research—is a system that meets the challenges of EWSNs using a hierarchical architecture that includes distributed reliable storage, delay-tolerant networking, and deployment time validation techniques.

In LUSTER, a fleet of sensors coordinate communications using LiteTDMA, a low-power cluster-based MAC protocol. They measure the complex light environment in thickets and are open to additional ecological parameters, such as temperature and CO₂.

LUSTER has been deployed and evaluated in laboratory, forested, and barrier island environments. It includes new sensor hardware designs: (a) “SolarDust,” a hybrid multichannel energy harvesting and sensing device; (b) “Medusa,” a spatially reconfigurable light sensor; (c) a removable SD card storage node; and, (d) in-situ user interface tool for deployment time validation.

Formats:

PDF

DEEJAM: Defeating Energy-Efficient Jamming in IEEE 802.15.4-based Wireless Networks

Citation:

Anthony D. Wood, John A. Stankovic, Gang Zhou, “DEEJAM: Defeating Energy-Efficient Jamming in IEEE 802.15.4-based Wireless Networks,” in The 4th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON), San Diego, CA, June 2007.

Summary:

Jamming is a very effective denial-of-service attack that renders most higher-layer security mechanisms moot—yet it is often ignored in WSN design. We show that an interrupt jamming attack is simple to perpetrate in software using a MICAz mote, is energy efficient for the jammer, and completely disrupts communication. Solutions are needed to mitigate this insider threat even if more powerful attackers are not thwarted.

We present DEEJAM, a novel MAC-layer protocol for defeating jamming with IEEE 802.15.4-based hardware, to address this problematic area. It layers four defensive mechanisms to hide communication from a jammer, evade its search, and reduce its impact.

Given the difficulty of modeling the physical layer accurately in simulation, we evaluate DEEJAM instead on the MICAz mote. We show the performance of the protocol against successively more complex attacks: interrupt jamming, activity jamming, scan jamming, and pulse jamming. Results show that DEEJAM defeats the otherwise devastating interrupt jammer, and achieves a packet delivery ratio of 88% in the presence of a pulse jammer.

To the best of our knowledge, this work is the first to confront multiple types of jamming on common WSN hardware with solutions that are shown empirically to enable continued communication despite an ongoing attack.

Formats:

paper PDF

slides PPT, PDF

Dynamic Privacy in Assisted Living and Home Health Care

Citation:

Gilles Virone, Thao Doan, Anthony Wood, Vijay Srinivasan, John Stankovic, “Dynamic Privacy in Assisted Living and Home Health Care,” accepted to Joint Workshop On High Confidence Medical Devices, Software, and Systems (HCMDSS) and Medical Device Plug-and-Play (MD PnP) Interoperability, June 2007. (short paper)

Abstract:

As wireless sensor networks become more and more powerful in their capability to sense and communicate data over wireless radio links, they are actively being investigated for assisted-living and home health care. In this paper, we present the design of a lightweight distributed framework for wireless sensor networks that protects a patient's privacy based on dynamic, context aware, privacy rules. The system utilizes the knowledge of activity patterns to help enforce privacy policies. Part of the privacy system has been implemented in AlarmNet, our medical wireless sensor network for Assisted Living. The current implementation shows the feasibility of adjusting in-network privacy rules depending on resident behavior, and other context aware conditions. We also discuss a new policy language for this domain and present problems and solutions for privacy protection against wireless snooping.

SIGF: A Family of Configurable, Secure Routing Protocols for Wireless Sensor Networks

Citation:

Anthony D. Wood, Lei Fang, John A. Stankovic, Tian He, “SIGF: A Family of Configurable, Secure Routing Protocols for Wireless Sensor Networks,” at The Fourth ACM Workshop on Security of Ad Hoc and Sensor Networks (SASN 2006), Alexandria, VA, October 2006. (Best Paper Award)

Abstract:

As sensor networks are deployed in adversarial environments and used for critical applications such as battlefield surveillance and medical monitoring, security weaknesses become a big concern. The severe resource constraints of WSNs give rise to the need for resource bound security solutions.

In this paper we present SIGF (Secure Implicit Geographic Forwarding), a configurable secure routing protocol family for wireless sensor networks that provides "good enough" security and high performance. By avoiding or limiting shared state, the protocols prevent many common attacks against routing, and contain others to the local neighborhood.

SIGF makes explicit the tradeoff between security provided and state which must be stored and maintained. It comprises three protocols, each forming a basis for the next: SIGF-0 keeps no state, but provides probabilistic defenses; SIGF-1 uses local history and reputation to protect against certain attacks; and SIGF-2 uses neighborhood-shared state to provide stronger security guarantees.

Our performance evaluation shows that SIGF achieves high packet delivery ratios with low overhead and endto- end delay. We evaluate the security of SIGF protocols under various security attacks and show that it effectively contains the damage from compromised nodes and defends against black hole, selective forwarding, Sybil, and some denial of service attacks.

Formats:

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An Advanced Wireless Sensor Network for Health Monitoring

Citation:

G. Virone, A. Wood, L. Selavo, Q. Cao, L. Fang, T. Doan, Z. He, R. Stoleru, S. Lin, and J. A. Stankovic, “An Advanced Wireless Sensor Network for Health Monitoring," at Transdisciplinary Conference on Distributed Diagnosis and Home Healthcare (D2H2), Arlington, VA, April 2-4, 2006.

Abstract:

In this paper we propose a system architecture for smart healthcare based on an advanced Wireless Sensor Network (WSN). It specifically targets assisted-living residents and others who may benefit from continuous, remote health monitoring. We present the advantages, objectives, and status of the design. An experimental living space has been constructed at the Department of Computer Science at UVA for evaluation. Early results suggest a strong potential for WSNs to open new research perspectives for low-cost, ad hoc deployment of multimodal sensors for an improved quality of medical care.

Formats:

PDF

Wireless Sensor Networks for In-Home Healthcare: Potential and Challenges

Citation:

J. A. Stankovic, Q. Cao, T. Doan, L. Fang, Z. He, R. Kiran, S. Lin, S. Son, R. Stoleru, A. Wood, “Wireless Sensor Networks for In-Home Healthcare: Potential and Challenges,” in High Confidence Medical Device Software and Systems (HCMDSS) Workshop, Philadelphia, PA, June 2-3, 2005 (position paper).

Summary:

We propose a wireless sensor network architecture for smart homecare that possesses the essential elements of: integration with existing medical practices and technology; real-time, long-term, remote monitoring; miniature, wearable sensors; and, assistance to the elderly and chronic patients.

Formats:

PDF

EnviroTrack: Towards an Environmental Computing Paradigm for Distributed Sensor Networks

Citation:

T. Abdelzaher, B. Blum, Q. Cao, Y. Chen, D. Evans, J. George, S. George, L. Gu, T. He, S. Krishnamurthy, L. Luo, S. Son, J. Stankovic, R. Stoleru, A. Wood, “EnviroTrack: Towards an Environmental Computing Paradigm for Distributed Sensor Networks,” IEEE International Conference on Distributed Computing Systems (ICDCS), Tokyo, Japan, March 2004.

Abstract:

Distributed sensor networks are quickly gaining recognition as viable embedded computing platforms. Current techniques for programming sensor networks are cumbersome, inflexible, and low-level. This paper introduces EnviroTrack, an object-based distributed middleware system that raises the level of programming abstraction by providing a convenient and powerful interface to the application developer geared towards tracking the physical environment. EnviroTrack is novel in its seamless integration of objects that live in physical time and space into the computational environment of the application. The performance of an initial implementation of the system is evaluated on an actual sensor network based on MICA motes. Results demonstrate the ability of the middleware to track realistic targets.

Formats:

PDF, PS

JAM: A Jammed-Area Mapping Service for Sensor Networks

Citation:

Anthony D. Wood, John A. Stankovic, Sang H. Son, “JAM: A Jammed-Area Mapping Service for Sensor Networks,” In Real-Time Systems Symposium (RTSS), Cancun, Mexico, 2003.

Abstract:

Preventing denial-of-service attacks in wireless sensor networks is difficult primarily because of the limited resources available to network nodes and the ease with which attacks are perpetrated. Rather than jeopardize design requirements which call for simple, inexpensive, mass-producible devices, we propose a coping strategy that detects and maps jammed regions. We describe a mapping protocol for nodes that surround a jammer which allows network applications to reason about the region as an entity, rather than as a collection of broken links and congested nodes. This solution is enabled by a set of design principles: loose group semantics, eager eavesdropping, supremacy of local information, robustness to packet loss and failure, and early use of results. Performance results show that regions can be mapped in 1–5 seconds, fast enough for real-time response. With a moderately connected network, the protocol is robust to failure rates as high as 25 percent.

Formats:

PDF

An Entity Maintenance and Connection Service for Sensor Networks

Citation:

B. Blum, P. Nagaraddi, A. Wood, T. Abdelzaher, S. Son, J. Stankovic, “An Entity Maintenance and Connection Service for Sensor Networks,” In The First International Conference on Mobile Systems, Applications, and Services (MobiSys), San Francisco, CA, May 2003.

Abstract:

In this paper, we present a middleware architecture for coordination services in sensor networks that facilitates interaction between groups of sensors which monitor different environmental events. It sits on top of the native routing infrastructure and exports the abstraction of mobile communication endpoints maintained at the locations of such events. A single logical destination is created and maintained for every environmental event of interest. Such destinations are uniquely labeled and can be used for communication by application-level algorithms for coordination and sensory data management between the different event locales. For example, they may facilitate coordination, in a distributed intrusion scenario, among nodes in the vicinity of the intruders.

We evaluate our middleware architecture using GloMoSim, a wireless network simulator. Our results illustrate the success of our architecture in maintaining event-related communication endpoints. We provide an analysis of how architectural and network dependent parameters affect our performance. Additionally we provide a proof of concept implementation on a real sensor network testbed (Berkeley's MICA Motes).

Formats:

PDF

A Communication Architecture and Programming Abstractions for Real-Time Embedded Sensor Networks

Citation:

T. Abdelzaher, J. Stankovic, S. Son, B. Blum, T. He, A. Wood, Chenyang Lu, “A Communication Architecture and Programming Abstractions for Real-Time Embedded Sensor Networks,” In 1st International Workshop on Data Distribution in Real-Time Systems (DDRTS at ICDCS), Providence, RI, May 2003.

Abstract:

Data distribution in embedded real-time sensor networks requires new protocols and programming environments that achieve time-sensitive message delivery and provide useful abstractions to the application programmer. Attainment of these goals requires changes to multiple layers of the communication protocol stack. In this paper, we review a protocol suite developed by the authors for data communication in embedded sensor networks. It takes into account time constraints and exports attribute-based connections that are tightly integrated with properties of the monitored environment. A programming language is described that allows external physical objects to be represented as first class abstractions in the computing system. The language facilitates writing monitoring applications. The system was implemented on a prototypical sensor network based on MICA motes.

Formats:

PDF

Join Point Encapsulation

Citation:

David Larochelle, Karl Scheidt, Kevin Sullivan, Yuan Wei, Joel Winstead, Anthony Wood, “Join Point Encapsulation,” In Workshop on Software-engineering Properties of Languages for Aspect Technologies (SPLAT) at AOSD 2003, Boston, MA, March 2003.

Abstract:

Current aspect-oriented languages do not provide means to control the exposure of join points for modification by aspects. Rather, they generally define certain classes of join points (e.g., method calls) and expose all their instances. In a nutshell, current languages lack join point encapsulation mechanisms. On its face, the lack of such language mechanisms denies program designers the option to prevent aspects from modifying program behavior at selected join points. Our position is that there is potential value in providing the designer with such control, and that it can be provided in a way that is consistent with fundamental tenents, mechanisms and styles of aspect-oriented language design. We discuss a design space for join point encapsulation mechanisms and we present an implemented prototype for AspectJ. The mechanism, itself, is aspect-oriented, using the AspectJ pointcut language to define cross-cutting sets of join points to be encapsulated against aspect modification. Such an encapsulation mechanism has potential benefit in easing reasoning and evolution.

Formats:

PDF

Book Chapters

Security of Distributed, Ubiquitous, and Embedded Computing Platforms

Citation:

Anthony D. Wood, John A. Stankovic, “Security of Distributed, Ubiquitous, and Embedded Computing Platforms,” to appear in Wiley Handbook of Science and Technology for Homeland Security, John G. Voeller, ed, John Wiley & Sons, Hoboken, NJ, 2009. (invited chapter)

Summary:

As embedded computer systems continue to explode in number and capability, security and privacy challenges abound. We review desirable security properties and the design constraints posed by these systems that make security difficult. We summarize current research by focusing on solutions for ad hoc networks, wireless sensor networks, and RFID tags as representative of the design space. State of the art protocols and approaches for defeating or mitigating attacks at the physical, network and middleware layers are presented. Critical application areas and research needs are identified, as are possible funding sources.

A Taxonomy for Denial-of-Service Attacks in Wireless Sensor Networks

Citation:

Anthony D. Wood, John A. Stankovic, “A Taxonomy for Denial-of-Service Attacks in Wireless Sensor Networks,” Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, CRC Press, 2004. (invited chapter)

Summary:

Wireless sensor networks (WSNs) are transitioning to real-world applications, where they face attacks already experienced by the Internet and wireless ad hoc networks. One such attack is that of denial-of-service (DoS), which we believe will only become more prevalent as sensor networks become more pervasive and accessible. With the inherent resource limitations of WSN devices, they are particularly susceptible to the consumption and destruction of these scarce resources. We present a DoS attack taxonomy to identify the attacker, his capabilities, the target of the attack, vulnerabilities used, and the end result. We survey vulnerabilities in WSNs and give possible defenses. Protecting WSNs against DoS attacks—while remaining low-cost and exible—is a primary research challenge that bears further exploration.

Formats:

pre-print PDF

Communication Architecture and Programming Abstractions for Real-Time Embedded Sensor Networks

Citation:

T. Abdelzaher, J. Stankovic, S. Son, B. Blum, T. He, A. Wood, Chenyang Lu, “Communication Architecture and Programming Abstractions for Real-Time Embedded Sensor Networks,” Handbook of Sensor Networks: Compact Wireless and Wired Sensing Systems, CRC Press, 2004 (invited paper).

Summary:

We review a new protocol suite and programming system for sensor network applications that may considerably improve real-time behavior and reduce the development cost of deeply embedded systems. This reduction comes from off-loading the details of managing low-level abstractions from the application developer.

Technical Reports

SenQ: An Extensible Query System for Streaming Data in Heterogeneous Interactive Wireless Sensor Networks

Citation:

Anthony D. Wood, Leo Selavo, John A. Stankovic, “SenQ: An Extensible Query System for Streaming Data in Heterogeneous Interactive Wireless Sensor Networks,” Technical Report CS-2008-1, Department of Computer Science, University of Virginia, 2008.

Abstract:

Interactive wireless sensor networks (IWSNs) manifest diverse sensors and dynamic user interactions. To support data collection and processing in such heterogeneous systems, we created SenQ: an extensible query system and network protocol for streaming sensor data. We evaluate it using a set of devices we developed for physiological, environmental, and activity monitoring in the context of assisted-living.

Rather than tree-based wide-area sensor aggregation common in environmental sensor networks, data processing patterns in IWSNs are user and event-driven. SenQ's query model and implementation are lightweight enough to allow in-network query issue by wearable interfaces and other resource-constrained devices. It standardizes access to sensor drivers and processing blocks for extensibility to new applications, and to allow complex virtual sensors to be created.

SenQ provides snapshot and streaming access to a dynamically reconfigurable in-network data processing chain, and supports aggregation in the temporal and spatial domains. On-demand buffering, query caching, efficient restart and other optimizations reduce network overhead while minimizing data latency.

Formats:

PDF

ALARM-NET: Wireless Sensor Networks for Assisted-Living and Residential Monitoring

Citation:

A. Wood, G. Virone, T. Doan, Q. Cao, L. Selavo, Y. Wu, L. Fang, Z. He, S. Lin, J. Stankovic, “ALARM-NET: Wireless Sensor Networks for Assisted-Living and Residential Monitoring,” Technical Report CS-2006-11, Department of Computer Science, University of Virginia, 2006.

Abstract:

We describe ALARM-NET, a wireless sensor network for assisted-living and residential monitoring. It integrates environmental and physiological sensors in a scalable, heterogeneous architecture. A query protocol allows real-time collection and processing of sensor data by user interfaces and back-end analysis programs. One such program determines circadian activity rhythms of residents, feeding activity information back into the sensor network to aid context-aware power management, dynamic privacy policies, and data association. Communication is secured end-to-end to protect sensitive medical and operational information.

The ALARM-NET system has been implemented as a network of MICAz sensors, stargate gateways, iPAQ PDAs, and PCs. Customized infrared motion and dust sensors, and integrated temperature, light, pulse, and blood oxygenation sensors are present. Software components include: TinyOS query processor and security modules for motes; AlarmGate, an embedded Java application for managing power, privacy, security, queries, and client connections; Java resident monitoring and sensor data querying applications for PDAs and PCs; and a circadian activity rhythm analysis program.

We show the correctness, robustness, and extensibility of the system architecture through a scenario-based evaluation of the integrated ALARM-NET system, as well as performance data for individual software components.

Formats:

PDF