Wireless Networking Group Research

The research in Wireless Networking Group spans over various issues in sensor networks and more general wireless networks. Sensor network is a new computing paradigm that has not been understood much. Our goal is to gain more in-depth understanding about many aspects of the sensor network; eventually we may have a panoramic view about how to design sensor network protocols effectively. More precisely, we have been working on the following aspects.

NEW!!!! Current Research Projects.


We use google everyday to search information on the Internet, but how do we search the objects in the physical world? For example, how do we find Thomas Jefferson's statue in College of William and Mary, how do we find your favorite CD with a specific title, how do I find where I put the tax return form, my computer architecture book? You use Snoogle. Snoogle is a search engine for the physical world. With the textual annotation to the objects by attaching RFID and sensors, the searching capability is extended to more tangible world we live in. We are not quite there yet, but Snoogle gives the architecture and framework for an experimental searching system for physical object searching.


William Blake in his famous poem wrote:
To see a World in a Grain of Sand
And a Heaven in a Wild Flower,
Hold Infinity in the palm of your hand
And Eternity in an hour.
Can we really search a world in a grain of sand? Nowadays, search pretty much means google. You use google desktop search to search whatever stored in your computer, but how far can this go? How small the computer can be so that you can still do search? Can we search the dancing angels on the tip of a needle (just joking)? Microsearch is a textual search system for tiny devices. It can run on small sensors (eventually smart dusts).

Sensor and RFID security

Someone asked the question: "How do the bacteria solve security problems?" This question indeed fascinates us. Honestly we don't know the answer, but we do know a bit how to do security for an ant or a bug if they carry small sensors or RFID tags. We have built a very efficient public key suite for sensors, which takes only around 1 second to do normal cryptographic operations. What does that mean? It means, when an ant comes back home, it waits one second to be authenticated so that it will be allowed to enter. Ants move slow, so we think one second is pretty good for them. If they carry RFID tag, and have no Internet connection, but they do need RFID readers, they can use our new authentication and search protocols. More amazingly, ants can do identity-based cryptography now. If one ant intends to send a message to his girlfriend, he does not need to know her public key--he merely uses her name to derive her public key. What a convenience for ant empire!

Sensor Network Storage


Sensor Network Security

We are currently exploring new methods in enhancing sensor network security. We have developed a suite of public-key based security primitives for TelosB and Mica Motes.

Partial Coverage

Sensor network coverage is to guarantee that obejects present in the network field will be detected. Partial coverage has not been investigated much while most of the people have worked on how to provide full coverage in a sensor network. Partial coverage, compared to full coverage, can increase the sensor network lifetime at the cost of decreased sensing quality. Many times, network lifetime is more important than the sensing quality. How to balance the lifetime and different sensing qualities is our main research. We have worked on a framework to analyze the fundamental bounds of the partial coverage performance.  We have given a simple but powerful random sensing schedule protocol that yields a very good performance. To achieve a good worst case performance, we have designed several wave-sensing schedule protocols as well that can guarantee the maximal detection time for any object in a network field. Wave-sensing schedule takes the analogy of a line sweeping through the field for object detection to enforce the sensors touched by the sweeping line to wake up and go back to sleep after the line passes.

Sensor Network Navigation

Sensor network navigation is a project to integrate several functionalities of a sensor network, including sensing, communication, data disssemination and query, into a useful application. The network uses very simple computation and communication to distribute the map information in the network. A user in a sensor field can query the network about where to go by avoiding the dangerous areas (fire, landmine, enemy, etc.). We analyzed the protocol, and tested the navigation protocol on a sensor network platform composed of 50 Motes. The recent improvement is to extend the original protocol to a more cost-effective Voronoi-diagram-based protocol, which requires less network search space for path optimization. Another interesting extension is task scheduling and assignment through the coordination of the sensor network.

Sensor Network Clock Synchronization

Clock synchronization is a basic service for sensor network applications, used in vehicle tracking, localization, power saving, and so on. We designed very simple localized and fault-tolerant protocols for global clock synchronization for the entire network.  The protocols are based on a diffusion process in which each node only conducts computation by knowing its neighbors, that is, exchanges its clock reading with its neighbors by considering the clock reading difference. We also show how to achieve synchronization in a localized way in the presence of the Byzantine fault. In this framework, sensor nodes may lie about its clock reading and may also corrupt the message relayed through it.

Power-aware Routing in Ad-hoc and Sensor Networks

Energy consumption is one of the most important performance metrics in wireless ad-hoc and sensor networks. In this study, we proposed power-aware routing protocols to maximize the lifetime of a network. The algorithm does not assume prior knowledge of the message sequence because for ad-hoc network applications this sequence is dynamic and depends on sensed values and goals communicated to the system as needed. It selects a compromise between the path with the minimum power consumption and the path that maximizes the minimal residual power in the nodes of the network. The goal is to avoid the nodes that have been depleted of power and at the same time choose a path that has less aggregate power consumption. We also extended the algorithm to a hierarchical structure and designed an algorithm that reduces amount of control messages.

Mobile Sensor Networks/Connectivity Maintenance in Disconnected Networks

Randomly deployed networks and mobile networks undergo disconnection or network partition all the time; maintaining connectivity is crucial to the normal function of a network. We proposed to use mobility to achieve network connectivity or information delivery even though time delay is introduced in this scenario. We consider two types of mobilites: controlled mobility and natural mobility. Controlled mobility means a network node can move under its own control, while natural mobility is characterized by a node that can only move by the control of its environment.