NOTE: The Center for Mobile Computing is no longer active, and this web site represents a historical view of its activities from 1996-2008. Although there is still mobile-computing research underway at Dartmouth, we no longer update this web site. Please contact David Kotz with any inquiries about the CMC.

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CMC Programs

The CMC loosely categorizes its activities as Major Programs or Individual Projects. This page lists Major Programs, which generally correspond to a DARPA or DoD program, include multiple technical projects, and have their own Web site. A separate page lists Individual Projects below, many of which are done under the auspices of one or more of the major programs. This page lists only some CMC programs; we will expand our coverage of CMC activities in the near future.

D'Agents
A mobile agent is a program that can migrate under its own control from machine to machine in a heterogeneous network. Mobile agents allow some applications to make more effective use of network resources by moving code to the network location of the data, rather than pulling large volumes of intermediate results back to the home machine. Mobile agents are particularly attractive in wireless networks or other low-bandwidth, unreliable network environments, and are best viewed as another tool that programmers can use to develop the most effecient distributed applications. The D'Agents program is a nine-year effort that has developed a mobile-agent system, D'Agents, and explored the performance, security, and applications of mobile agents and other forms of mobile code.

Active Communications
The ActComm project seeks to provide soldiers with wearable computers and wireless data communications, and on top of this infrastructure, various mission-support capabilities. The ActComm project is a Multi-disciplinay University Research Initiative (MURI), funded by the Department of Defense and administered by the Air Force Office of Scientific Research. ActComm participants are Dartmouth College, Harvard University, RPI, the University of Illinois, Lockheed Martin - ATL, and ALPHATECH. Technical projects under ActComm include ad-hoc wireless routing algorithms, network sensing and prediction techniques, and applications of mobile code.

Control of Agent-Based Systems (CoABS)
The CMC's CoABS program is part of DARPA's CoABS program, which has over forty participating institutions looking at different aspects of agent-based systems and programming. The CMC has focused on resource control and scheduling algorithms for mobile agents, mobile-code performance and scalability, and interoperability middleware for mobile-agent systems.

CMC Projects

This page lists some of the CMC Projects. The dates associated with each project indicate when the project description was written, and where possible, we provide links to people or pages that have more recent information.

Data Assurance in Medical Sensor Applications
2007

We expect that wearable, portable, and even embeddable medical sensors will enable long-term continuous medical monitoring for many purposes, such as patients with chronic medical conditions (such as the recently announced blood-sugar sensors for diabetics), people seeking to change behavior (e.g., losing weight, or quitting smoking), or athletes wishing to monitor their condition and performance. The resulting data may be used directly by the person, or shared with others: with a physician for treatment, with an insurance company for coverage, or by a trainer or coach. Such systems have huge potential benefit to the quality of healthcare and quality of life for many people.

Since the sensor data may be gathered through a patient's mobile device (such as a mobile phone), a wireless network, and the Internet, there are many opportunities for the sensor data to be tampered or otherwise inaccurate. How can we assess confidence in sensor data? How can we present that level of confidence, in context, with the sensor data? This project will develop methods to assess confidence in medical sensor data.

Funded by the Intel University Research Council.

MetroSense: scalable secure sensor systems
September, 2006

Sensor networks will provide a foundation to protect and monitor our national infrastructure, including economically important businesses with global reach (e.g., stock markets), critical transport and industrial facilities, the enterprise, and the border. These tiny, low-cost wireless devices embed on-board sensing, are fully programmable, and can spontaneously form large sensor webs with thousands of distributed sensor devices. In this project, we will study, analyze, propose, deploy, and evaluate MetroSense, a radically different scalable secure sensor architecture and system capable of reliable real-time monitoring and data fusion for large-scale critical infrastructure, resources, and assets. MetroSense opportunistically leverages mobile sensors when available to deal with sparse coverage and communications when sensing. We plan to develop a campus-area sensing architecture based on three integrated components (sensing and communications, sensor security, and sensor fusion) and deploy the system incrementally across campus with the goal of using static and mobile sensors for reliable monitoring and data fusion of campus plant, spaces, and people flow. Results from this project will serve as a foundation for building secure sensor networks capable of monitoring large-scale critical infrastructure.

CRAWDAD: a Community Resource for Archiving Wireless Data at Dartmouth.
July, 2005
http://crawdad.cs.dartmouth.edu/

As a community resource, the CMC is building an archive with the capacity to store wireless trace data from many contributing locations, with the staff to develop better tools for collecting, anonymizing, and analyzing the data. This Community Resource for Archiving Wireless Data At Dartmouth, CRAWDAD, will work with community leaders to ensure that the archive meets the needs of the research community, work with the other leading centers that develop network tracing tools and metadata, and work with research organizations and corporations to ensure continuing support for the archive after NSF's funding ends.

Older CMC projects

Real Time Monitoring of a Wireless Mesh Network for Emergency Response Operations
Soumendra Nanda and David Kotz
July, 2005

Wireless mesh networks can be used to provide communication infrastructure for emergency response operations in areas with limited or damaged infrastructure. We imagine the formation of a wireless mesh of heterogeneous devices such as transceivers on ambulances, fire trucks and police cars. This mesh would support a network of Personal Digital Assistants (PDAs) on first responders and an ad hoc network of rapidly deployed micro-sensor devices. Monitoring of such a mesh network will be crucial to the success of first responder operations. Standard techniques for monitoring wired networks or even wireless infrastructure networks are unsuitable for a wireless mesh network with unpredictable links and resource-constrained devices. Our goal is to develop a wireless mesh monitoring system to detect and identify real-time problems and aid system administrators in making proactive as well as reactive management decisions.

We propose to develop a mesh monitoring system that can be used to generate real-time network topology maps, power maps and provide real-time data on network traffic and user locations to aid mission planners. The aim of this project is to present new ways to efficiently implement a real-time wireless monitoring system that assists in fault detection, repair and the automation of network management tasks. It may also be possible to use the monitored information about the state of the network to improve and optimize the performance of the mesh routing protocol. Some other contributions of this work will be in the use of error codes to recover information from corrupt or lost packets and to maximize utility of monitoring information sent over an unreliable channel. Our initial plan is to deploy a 15-node multi-radio mesh network and to monitor it using in-band channels as well as out-of-band channels (such as a wired backhaul or a separate wireless channel) for the traffic being monitored. Thus we can study the effectiveness of the monitoring system and its impact on the behavior of the mesh network. In parallel, we will simulate a mesh network to study scalability and other characteristics of the monitoring system.

Digital Living: Understanding PLACE (Privacy in Location-Aware Computing Environments)
Faculty: Denise Anthony, Andrew Campbell, David Kotz (lead), Tristan Henderson
Staff: Ronald Peterson
July, 2005

Digital technology plays an increasing role in everyday life, and this trend is only accelerating. Consider daily life five years from now, in 2010: we will each be surrounded by far more digital devices, mediating far more activities in our work, home, and play; the boundary between cyberspace and physical space will fade as sensors and actuators allow computers to be aware of, and control, the physical environment; and the devices in our life become increasingly (and often invisibly) interconnected with each other and with the Internet. Today, typical home users struggle to maintain the security of their home computer, and have difficulty managing their privacy online. Tomorrow, these challenges may become unimaginably complex. This 18-month project studies, and begins to address, the security and privacy challenges involved in developing this world of Digital Living in 2010.

Specifically, this project focuses on the advent of sensor networks, and their applications in the home and work environment. Although sensor networks have been an active area of academic research, and are becoming commercially available for deployment in industrial settings, sensor networks will soon have many uses in enterprise and residential settings. People will live in spaces, or work with devices, that have embedded sensing capability. For people to accept this new technology into their lives, they must be able to have confidence that the systems work as expected, and do not pose unreasonable threats to personal privacy. This confidence results from a variety of technical and organizational mechanisms. This project delves into the sociological underpinnings of privacy and trust in digital living, into the technological foundations for secure and robust sensor networks, and into mechanisms for users to express control over information about their activity.

MAP: Measure, Analyze, Protect: Security through measurement for Wireless LANs.
July, 2005
http://www.cs.dartmouth.edu/~map/

With the rise of Voice over wireless LAN (VoWLAN), any complete WiFi security solution must address denial of service attacks, such as kicking off other clients, consuming excessive bandwidth, or spoofing access points, to the detriment of legitimate clients. Even authorized clients may be able to sufficiently disrupt service quality to make the network ineffective for legitimate clients. Our approach provides a new foundation for wireless network security, able to dynamically measure, analyze and protect a WiFi network against existing and novel threats, including rogue clients and access points, with a focus on VoWLAN use cases. Our goal is to support thousands of APs and clients, quickly recognize most new attacks, and generate few false alarms.

Automated Remote Triage and Emergency Management Information System
May, 2005
Susan McGrath, Bob Gray, George Blike, Stephen Linder, Christopher Carella, Janelle Chang, Michael De Rosa, Aaron Fiske, Curtis McClurkin, Suzanne Wendelken

The Automated Remote Triage and Emergency Management Information System (ARTEMIS) is an ongoing research effort at Dartmouth College's Institute for Security Technology Studies that aims to provide real-time physiological information to first responders and command personnel in emergency/disaster situations. The prototype system is capable of monitoring and assessing physiological parameters of individuals, transmitting pertinent medical data to and from multiple echelons of medical service personnel, and providing filtered data for command and control applications.

The system employs wireless networking, portable computing devices, and reliable messaging technology as a framework for information analysis, information movement, and decision support capabilities. Physiological status assessment is based on a medical model that relies on input from humans and a pulse oximetry device. Our physiological status determination methodology follows NATO defined guidelines for remote triage and is implemented using an approach based on fuzzy logic. The approach described on this website can be used in both military and civilian settings.

The long-term goal of the ARTEMIS project is to integrate advances in communications and analysis technologies into a remote triage system that can expedite and improve care of the wounded in small-to-large scale emergency situations. Our aim is to provide an unprecendented degree of medical situational awareness at all levels of the first-responder command heirarchy.

Mobility modeling
April, 2005
Minkyong Kim, David Kotz

Many people who design, develop, or deploy wireless networks use simulations to evaluate the impact of their design decisions on the performance of the network. For these simulations to be effective, however, one must have a realistic model of device mobility. Currently available models of device mobility do not reflect the movement patterns of real users. Using the traces collected by access points (APs) on our campus, we aim to develop realistic mobility models.

We are interested in developing models of both AP-association patterns and physical user movements. The former presents how mobile users roam from one AP to another, while the latter describes how mobile users move in a physical space. To develop an association model, we first extract the characteristics of association patterns directly from the syslog messages (available on this site). We then derive an association model from these characteristics. To develop a physical-mobility model, however, we first need to estimate the physical location of users from the association patterns; this task is not easy because a mobile device does not necessarily associate with the geographically-closest AP. Our path extractor estimates paths from AP-association patterns and has been validated against GPS track data as shown in the figure. These extracted paths are used for developing a physical-mobility model.

WLAN User Mobility Prediction
April, 2005
Libo Song, Udayan Deshpande, David Kotz, Ravi Jain, Ulas Kozat, and Xiaoning He

In wireless networks users can move from one location to another location without losing their network connection. This flexibility of mobility introduces new challenges in quaranteeing quality of service (QoS) and in locating users and transfering data between them and the access points (APs). By predicting a user's next AP we can reduce the overhead of mobility management and make bandwidth reservations to guarantee the QoS.

Many prediction algorithms have been proposed, but most of them are evaluated by simulations using synthetic data. We have collected the association messages at our campus-wide wireless network. From the association messages, we extracted the mobility traces, and evaluated prediction methods using our real wireless mobility data. We found that low-order Markov predictors performed as well or better than the more complex and more space-consuming compression-based predictors.

Besides predicting the next AP, anticipating a user's handoff time is also important for applications such as bandwidth reservation, which needs to know when to reserve bandwidth. It is easier to estimate the handoff probability with a period of time than to predict the exact time. We developed such a time predictor and combined it with a location predictor to compute the probability that a user handoffs to a certain AP within a given period of time. We simulated several bandwidth reservation schemes using this location-and-time-integrated predictor with our real mobility data. The results show that both call-drop rate and call-block rate are reduced significantly.

Since our simulation indicates that with accurate location-and-time prediction the QoS of calls is improved, we would like to improve the performance of predictors. In the future, we will continue to collect wireless association data and investigate the characteristics of users mobility patterns. We believe these mobility characteristics will help us develop better predictors.

Guiding People and Robots with Sensor Networks
March, 2005
Daniela Rus, Ronald Peterson, Peter Corke, Gaurav Sukhatme, Srikanth Saripalli, Stefan Hrabar

A wireless sensor network can extend the sensory perception of people and robots far beyond their normal range. Wireless sensors are also small computers. When the sensors are used to detect danger they can perform distributed computations to compute the safest path along which a person or robot can be guided. Sensors that detect their own network connectivity can be used to guide a robot to repair holes in that connectivity. Sensors that detect a fault in an industrial process can guide a robot or person to the location of the fault for further inspection. Robots and people can also store information in a sensor network which can later be used for guidance, or by the sensor network itself (for example by telling the sensors their GPS coordinates.)
We have been exploring all these concepts in a large variety of experiments. In the picture on the right, USC's AVATAR autonomous flying robot is repairing the gaps in connectivity in a sensor network. The sensor network computed the locations of missing sensors, the robot queried the network for the gap location, and then flew over the gap, dropping new sensors to repair the network.
In the picture on the left, a crane robot at CMU is interacting with a sensor network. The robot is controlled by precision winches connected to the four cables attached to the robot from the ceiling. This type of robot might be used inside a factory to maintain sensors that monitor industrial processes. The robot first broadcasts location messages while moving in a precise pattern to localize the sensors. A radio message was then broadcast to the sensor network and followed a precise geographic path through the sensors. The robot then queried the sensors to follow the same path as the radio message.
We have also been looking at using maps of sensed data to guide people and robots. The picture on the left shows a temperature map as it varies over time in a room where a large fire has been started. Guidance algorithms can make use of such maps to bring people to safety, or to guide firefighters to the danger.
A device we call a "flashlight", shown in the center of the sensors in the picture below, can be carried by a person or robot to find their way through an area based on the data stored in the sensors or on the readings from the sensors.

Quality-managed Group-aware Stream Filtering
November, 2007
Ming Li, David Kotz

This project considers a distributed system that disseminates high-volume data streams to many simultaneous monitoring applications over a low-bandwidth network. For bandwidth efficiency, we propose a group-aware stream filtering approach, used together with multicasting, that exploits two overlooked, yet important, properties of monitoring applications: 1) many of them can tolerate some degree of ``slack'' in their data quality requirements, and 2)there may exist multiple subsets of the source data satisfying the quality needs of an application. We can thus choose the ``best alternative'' subset for each application to maximize the data overlap within the group to best benefit from multicasting. Here we provide a general framework for the group-aware filtering problem, which we prove is NP-hard. We introduce a suite of heuristics-based algorithms that ensure data quality (specifically, granularity and timeliness) while preserving bandwidth.

Our work exploits applications' semantics to better managing precious network resources. For evaluation, we integrate group-aware filtering with a general-purpose sensor data dissemination middleware system, Solar, developed at Dartmouth College. Our evaluation shows that quality-managed group-aware filtering is effective in trading CPU time for bandwidth savings, compared with self-interested stream filtering.

Measuring Wireless Networks
March, 2005
Tristan Henderson, David Kotz, Denise Anthony

IEEE 802.11 Wireless Local Area Networks (WLANs) are now commonplace on many academic and corporate campuses. As “Wi-Fi” technology becomes ubiquitous, understanding trends in the usage of these networks becomes increasingly important for network deployment, management, and the development of new wireless and location-aware applications. We have been measuring various aspects of Dartmouth's campus-wide WLAN since the installation of the network in 2001. The extensive coverage of Dartmouth's WLAN allows us to study how the network is used by students, faculty and staff.

We employ a variety of methods to measure wireless network usage. We have deployed “sniffer” boxes (Linux PCs with multiple network interfaces) around the campus to observe the data packets that are transferred over the network; this enables us to measure wireless application usage. By using SNMP and syslog to monitor the access points we can measure user mobility patterns. We have also deployed wireless sniffers to measure the 2.4GHz and 5GHz frequency bands that are used by IEEE 802.11a/b/g networks; this allows us to measure wireless traffic that does not traverse the wired side of the Dartmouth network, and also lets us observe other wireless networks, such as ad-hoc networks or “rogue” access points. Finally, we are also investigating the use of psychological methodologies, such as the Experience Sampling Method, to ask the network users themselves about their experiences with the wireless network.

We have discovered that since the deployment of the network, usage has moved away from non-realtime applications such as the World Wide Web, with an increasing amount of streaming audio/video and peer-to-peer file transfers being conducted over the WLAN. Although Dartmouth has migrated to a Voice over IP telephone system, we have seen little wireless VoIP usage. We encourage other researchers to make use of the data that we have collected, and anonymised datasets are available on CRAWDAD.

Mobile Sensors for First Responders
March, 2005
Ron Peterson, Daniela Rus

In many emergency calls the presense of deadly, invisible chemicals is first noticed when people start coughing or falling ill. Even after the presence of a toxin has been verified, unless visible it is difficult to avoid exposure due to air motion. Networks of mobile chemical sensors (sensors on robots) can provide a first warning of nearby toxins, and tell us where they are, where they are moving towards, and how to avoid them.
As part of ongoing work in medical and environmental sensors for first responders, we devised a simulated air crash scenario that involves a chemical leak. The crash throws some debris into a nearby farmers field where a tank of anhydrous ammonia used as fertilizer is present on a trailer attached to a tractor. Anhydrous ammonia, when released into the atmosphere, is a clear colorless gas, which remains near the ground and drifts with the wind. It attacks the lungs and breathing passages and is highly corrosive, causing damage even in relatively small concentrations. It can be detected with an appropriate sensor such as the Figaro TGS 826 Ammonia sensor. Our experiments map the presence of an ammonia cloud and guide a first responder to safety along the path of least chemical concentration. The image on the right shows such a danger map with the safest path computed by a network of 38 Mica Mote sensors.
We are currently exploring the utility of mobile sensor networks in warning, guidance, and sensing for search and rescue missions in the difficult environments created by disaster situations, such as the rubble pile from a destroyed building shown to the left.

Mobile Computers for Herding Cattle with Virtual Fences
March, 2005
Daniela Rus, Ronald Peterson, Peter Corke, Zack Butler

Fences on open ranges cost the cattle industry a lot of time and money to install and maintain. Herding cattle also involves much time and effort. A collaboration between Daniela Rus, the CSIRO Robotics Team in Australia and a USDA Ranch Management Research Animal Scientist was initiated at Dartmouth to consider the problem of monitoring and controlling the position of herd animals.

The goal is to apply the vast body of theory in robotics and motion planning to virtual fences for controlling animals and to integrate new technologies, such as wireless adhoc networking, into a field where technology has yet had little penetration. Similar to the "invisible fence" products sold for fencing pets in the yard at home, a virtual fence is a collar or tag worn by an animal which tracks its location via GPS and applies a stimulus to the animal to control its motion. Animals are not robots and their unpredictable reactions mean that existing robotics motion control solutions must be modified to take into account the imprecise control before they can be useful.

The picture on the upper right shows a cow wearing an early prototype of a Smart Collar during an experiment. The picture on the lower left shows an automatic path planner for herding animals around obstacles to a goal. The picture on the lower right shows another early Smart Collar prototype with a PDA, adhoc WiFi multihop networking, GPS, and sound system for producing stimuli.

Security and access-control in context-aware computing
Kazuhiro Minami, David Kotz
August, 2005

In pervasive computing, many applications will be context-aware; that is, the applications adapt their behaviors according to user's situation or environment. We are examining the potential for making authorization decisions (such as access to a medical database) based on the context of the user making the request. Such a context-sensitive authorization scheme is necessary when mobile users (e.g., first responders) move across multiple administrative domains where they are not registered into the systems in advance. For example, in the First Responder project, a granting decision could depend on a requester's current location or medical conditions, which is obtained from the information servers. The information servers, in return, collect situational information from a sensor network that covers an emergency area. Since context information, such as the location of the user, might allow an malicious party to infer the user's private information, we particularly address the issue of protecting confidential information involved in authorization policies to protect the users' privacy.

We developed a secure logic-based authorization system where authorization policies are expressed as logical rules (i.e., Horn clauses). A request is granted if the authorization server succeeds in constructing a proof tree that derives the granting decision. Our decentralized scheme does not need a universally trusted central authorization server that maintains all the context information; the authorization decisions are made by multiple hosts, each of which only has partial knowledge about the context information, in a peer-to-peer way. Our novel distributed algorithm decomposes a proof tree into multiple subproof trees produced by different hosts so that confidentiality policies of each host are satisfied. We are deploying our current implementation into an emergency response system to evaluate the performance and scalability of the system.

Greenpass: Decentralized Authorization in Wireless Networks
July 2004
Sean Smith

Agent Based Casualty Care (ABC Care)
October 2003
Susan McGrath

The goal of the ABC Care project is to integrate advances in communications and analysis technologies into a combat casualty care system which can expedite and improve the care of wounded soldiers. The ABC Care prototype is capable of monitoring and assessing physiological parameters of individual soldiers, transmitting pertinent medical data to and from multiple echelons of medical personnel, and delivering treatment protocols. ABC Care employs mobile agent technology as the framework for information analysis, movement, and decision support capabilities. Medical models and physiological status assessment are based on input from humans and a pulse oximeter. The physiological status determination methodology follows NATO defined guidelines and is implemented using an approach based on fuzzy logic.

Analysis of the campus-wide wireless network and the impact of VoIP
September 2003
David Kotz

Dartmouth College has a campus-wide WiFi network with over 560 Cisco access points. In our previous work we extensively characterized the nature of WiFi usage by over 3000 campus WiFi users, data that has been significantly useful to network planners, network designers, and application developers. Today, we are replacing our campus telephone system with a complete Cisco VoIP solution, installing over 6000 Cisco VoIP phones and SoftPhones in the next two years. We expect many SoftPhones and WiFi handsets to be in use, so VoIP should have a significant impact on our wireless network. We will take advantage of this incredible opportunity to monitor our wireless network before and after the introduction of wireless VoIP clients, to measure the characteristics of voice users and their traffic, to measure the load on the wireless network, and to evaluate the impact of voice on the Cisco access points and on the network.

The Bear/Enforcer Project
September 2003
Sean Smith

How can you verify that a remote computer is the "real thing, doing the right thing?" High-end secure coprocessors are expensive and computationally limited; lower-end desktop enhancements like TCPA and the former Palladium have been mainly limited to Windows and proprietary development.

In contrast, this code is part of our ongoing effort to use open source and TCPA to turn ordinary computers into "virtual" secure coprocessors---more powerful but less secure than their high-assurance cousins.

The Linux Enforcer Module is a Linux Security Module designed to help improve integrity of a computer running Linux. The Enforcer provides a subset of Tripwire-like functionality. It runs continuously and as each protected file is opened its SHA1 is calculated and compared to a previously stored value. More information about this project and a recent paper can be found at this Dartmouth Technical Report TR2003-17 as well as the Enforcer Sourceforge site

Spatial Multipath Location Aided Ad Hoc Routing
August 2003
Soumendra Nanda, Robert Gray

Mobile ad-hoc networks (MANETs) are infrastructure free networks of mobile nodes that communicate with each other wirelessly.Our goal is to utilize three-dimensional (3D) position information to provide more reliable as well as efficient routing. We thus describe extensions to various location aware routing algorithms to work in 3D. We propose a new hierarchical, zone-based 3D routing algorithm, based on GRID by Liao, Tseng and Sheu. Our new algorithm called "Hyper-GRID" is a hybrid algorithm that uses multipath routing in 3D.

We wish to implement a multipath algorithm similar to AOMDV in Hyper-GRID as we expect to see lower end-to-end delays, lower packet loss and reduced routing overhead by reducing the frequency of route discovery phases through use of a multipath routing strategy.

Context-aware pervasive computing
February 2003
David Kotz, Guanling Chen, Kazuhiro Minami

The Solar project is using the campus wireless network, as well as a location-tracking system developed by Versus Technologies and installed in the computer-science building, to investigate the potential for location-aware applications and for pervasive computing in general.Kotz and his students are developing a flexible and secure infrastructure to collect, process, and disseminate location and other contextual information to context-aware applications; prototyping location-aware and context-aware applications, both in a campus setting and in emergency-response scenarios.

Their Solar System is a software infrastructure that supports context collection, aggregation, and dissemination. Solar provides a small composition language, allowing applications to construct a graph of operators to compute desired context from appropriate sources. Solar implements a context-sensitive resource discovery mechanism to achieve flexibility, and improves the scalability by balanced distribution and reuse of operators.

Location-aware applications in education
February 2003
Ted Cooley

Professor Cooley at Thayer School of Engineering and Newbury Networks have teamed to install Newbury's Locale Points within the Engineering School. Now, a user with a wireless-enabled TabletPC, notebook, of PDA is pushed web content depending on whether they are standing in the reception area, working in a computer lab, taking a class, etc. Thus, welcome information, how to get help, or class notes can be easily provided to the user.

An example project currently underway to take advantage of this location technology is Multimedia Techniques for Engineering Instruction, MTEI. With this system, course materials for specific courses, offered at specific times are wirelessly delivered to students in a given classroom. The MTEI system is also use for online quizzes for credit, and anonymous assessment to gauge whether the class is understanding a particular point or not. The latter results are displayed on the, "clue meter", a web-based gauge of student understanding.

Guiding Navigation across a Sensor Network
December 2002
Daniela Rus, Qun Li, Michael DeRosa, Ron Peterson

We develop distributed algorithms for self-reconfiguring sensor networks that help direct an object (say, a soldier or a robot) through a dangerous region. The sensor network models the danger levels sensed across its area, representing the dangerous areas as obstacles. A protocol that combines the artificial potential field of the sensors with the object's goal location guides the moving object incrementally across the network to the goal, while maintaining the safest distance to the danger areas. To evaluate the performance of the algorithms, we have done many hardware experiments using a physical sensor network consisting of Berkeley's Mote sensors.

Power-aware Protocols in Sensor Networks
December 2002
Javed Aslam, Daniela Rus, and Qun Li

We develop online power-aware routing algorithms in large wireless ad-hoc networks for applications where the message sequence is not known. We seek to optimize the lifetime of the network. We develop a series of approximation algorithms to solve the problem, including the centralized max-min zPmin algorithm, hierarchical algorithm, and several distributed algorithms that can reduce the message broadcasts on each node. Our experiments show that the performance is quite good. We are also working on the MAC-layer protocols to conserve energy by putting nodes into sleeping mode.

Communication and Exploration in Mobile Sensor Network
December 2002
Daniela Rus and Qun Li

Mobile sensor networks are a new form of sensor network in which the sensors are tethered to some moving equipment, such as wheels or flying objects. We study how the sensors can reconfigure themselves to achieve better network connectivity, message transmission, and other group behaviors. We developed algorithms to guarantee message delivery in a disconnected mobile sensor network by asking mobile sensors to move. Our next task is to develop algorithms for a mobile sensor network to explore a large area.

Semantic Sensor Networks
November 2002
Glenn Nofsinger and George Cybenko

Our research focuses on how to integrate battlefield information systems in a dynamic information environment to support information exploitation. Our goal is to create greater semantic interoperability among sensors and information assets. Our wireless sensor platform currently uses a hybridization of WiFi, 900 Mhz Spread Spectrum, GPS, and Dartmouth designed MiniME GPS sensors. Sensor measurements include sound, temperature, and seismic vibrations. These measurements are combined with a variety of data fusion algorithms distributed across the network.

Greenwave Wireless
November 2002
Chris Lentz and Zach Berke (not formally affiliated with CMC)

Two students are installing private APs in off-campus residences, and configuring them as repeaters. The goal is to expand the reach of the campus wireless network into private residences nearby. They route wireless traffic into the on-campus APs and thence to the campus backbone and the Internet. As a result we are getting valuable early experience with the realities of repeaters and mesh technologies.

Former CMC Projects

Network mapping
February 2003
David Kotz, Cal Newport, Chris Lentz

We plan to develop algorithms and technology for real-time mapping of the network's signal characteristics, using the existing infrastructure APs as sensors and using SNMP to collect the necessary data. One goal of this project is to improve the quality of the network models that are frequently used to analyze and validate routing algorithms for ad-hoc and mesh networks. Preliminary results show that signal strength between two stationary access points is substantially asymmetric, and that distance does not correlate well with signal strength.

Tacos Wireless Device Tracking System
November 2002
Chris Lentz and Zach Berke (not formally affiliated with CMC)

Market-based resource control
June 2001
Jon Bredin, Ph.D '01

Jon used ideas from economics to develop a market-based approach to the allocation of resources in a distributed system. In his approach, computations are mobile agents that need to jump from host to host to reach the resources they need. They must pay for the computation time they use at each host. The resulting market is an efficient mechanism for fair, distributed allocation of computational resources. In the fall Jon will be a professor in the Mathematics and Computer Science department at Colorado College.

Scalable directory for mobile users
June 2001
Ammar Khalid '01

Ammar developed a secure, scalable directory service for mobile users, and applied it to the mobile voice-over-IP application developed by Ayorkor. Chief among its goals was protecting the privacy of mobile users, so that a stalker cannot track the IP address (and thus the location) of a moving user. For his work, Ammar was awarded High Honors and shared the Kemeny Prize for Computing.

Mobile Voice-over-IP
June 2001
Ayorkor Mills-Tettey '01

Ayorkor extended the H.323 telephony protocols so that a voice-over-IP conversation can continue even as the mobile user's computer roams from access point to access point, and from IP subnet to IP subnet, changing IP addresses. For her work, Ayorkor was awarded High Honors and shared the Kemeny Prize for Computing.

SmartReminder
June 2001
Arun Mathias '01

Arun implemented the first application for Guanling Chen's Solar system. His SmartReminder application reminds its user of upcoming appointments depending on the current location and the location of the next appointment. For his work, Arun was awarded High Honors and shared the Kemeny Prize for Computing.

Characterizing the use of Dartmouth's wireless network
June 2001
Pablo Stern '01 and Kobby Essien '02

Geographically Distributed Sensors
March 2001
Michael G. Corr and C. M. Okino

Michael designed and built a collection of small sensor modules, each with a small processor and RF network link. When turned on, his modules quickly identify their neighbors in the ad-hoc wireless network and use a novel GPS-based routing algorithm to communicate their sensor readings to a central collection point.