Wireless Networks
Society is
rapidly approaching a pervasive computing environment in which a variety of
devices communicate constantly with each other, organizing themselves,
gathering information from the environment, and responding by actuating a
range of robotic devices. Key to the flexibility and effectiveness of these
systems is the ability to communicate without the limits imposed by phone
lines, cables, or cell phone towers, but ad hoc wireless communications
impose new challenges on researchers, including bandwidth constraints,
increased errors, the need for self-organization, and the energy limits
inherent in many deployed sensor and actuator systems. Members of
Rensselaer’s Center for Pervasive Computing are working on all levels of the
technology needed, from new physical devices to improved routing of
messages.
High-Speed Optical
Networks
With
funding from the National Science Foundation (NSF),
Shivkumar Kalyanaraman,
associate professor,
and
Partha Dutta, assistant
professor, both of electrical, computer, and systems engineering (ECSE), are using inexpensive LEDs (light-emitting diodes) and
microelectronics techniques to create a multihop wireless system with the
capacity to bring broadband optical connections to homes. They have
developed techniques through which the nodes can discover that they’re
aligned and then pass messages back and forth. Dr. Kalyanaraman is also
working with students in Rensselaer’s undergraduate research program on a
nearer-term project to bring broadband wireless capacity to homes in an area
within a mile of the Rensselaer campus. This project initially uses Pringles
cans to create radio frequency (RF) antennas, but it eventually will include
both RF and optical components as well as GPS positioning and new routing
software. The goal is to demonstrate an inexpensive system, which can be
upgraded as technology advances, with the goal of uniting communities around
the world.
Once a wireless community network is formed, a group including Dr.
Kalyanaraman has Army funding to investigate ways to prioritize messages
sent using the popular IEEE 802.11 MAC (media access control) protocol. They
are developing joint source network coding that will route high-priority
messages over the fastest routes, while using slower routes for less
important messages. In a complementary project, ECSE Professor and
Department Chair
Kenneth Connor and Adjunct
Professor
Ted Anderson are developing
smart plasma antennas, similar to fluorescent tubes or neon signs. Since
they disappear when not in use, they could be particularly valuable for
military applications.
Wireless Networks
A number of Rensselaer researchers are developing methods to make wireless
networks more reliable and efficient, including:
Failure Predictions ECSE Professor
Kenneth Vastola
and former graduate student Lisa Shay, now a professor at West Point,
created a wireless communications system that can recognize when a link is
about to fail. The system is designed for situations in which small mobile
units or individual soldiers must communicate on ad hoc wireless systems,
with their movements sometimes taking them out of range or behind a building
or hill. The system predicts such failures as much as 30 to 40 seconds in
advance, giving time to alert superiors and get instructions.
Compression to Minimize Costs When sending multimedia messages over ad
hoc wireless networks, packets of information should be compressed to reduce
congestion and transmission times along the route. But compressing the
messages makes them more sensitive to channel impairments, as losses of a
single packet can render the entire message unreadable. Since packets of
information travel different distances, with some passing through highly
congested routes and others processed by less-occupied nodes, one must vary
the degree and mode of compression and error correction coding, depending
upon the network path and the channel conditions along that path. Power
consumption is also an important trade-off.
Alhussein Abouzeid,
ECSE assistant professor, and
William Pearlman,
ECSE professor and director of the Center for Image Processing Research, are
working on a project known as COCO, which tries to optimize computation and
communication costs in multimedia wireless networks. They are developing
power-aware algorithms, based on RPI’s award-winning image compression
algorithm, SPIHT (Set Partitioning in Hierarchical Trees), to detect and
manage congestion and power consumption by jointly optimizing compression
and error correction coding.
Packet Routing
Costas Busch, assistant professor of
computer science, studies packet routing problems and is interested in a
concept of fairness in which all users are satisfied. He is working on
power-aware reversal routing in mobile ad hoc networks, in which nodes that
are overburdened by messages or that lose power reverse themselves, forcing
packets to take another route. With
Bulent Yener,
associate professor of computer science, he is also working on methods to
synchronize nodes in wireless networks to minimize packet collisions and
save energy.
Choosing the Best Channels
Gary Saulnier,
ECSE associate professor, is developing coding to help messages being sent
on wireless networks make the most efficient use of physical resources such
as antennas. He is creating a system to optimize transmissions when a group
of users depends on a particular suite of carriers. The self-learning system
probes channels to determine if they are already in use and chooses those
most able to carry the messages.
Distributed Sensor
Networks and Robotics
A large group of Rensselaer researchers works on distributed networks of
sensors and actuators,
devices
to learn about the environment and to react in specific ways. Key challenges
include limited power, the requirement for real-time information, and the
need for systems that can self-organize and reconfigure themselves. A few of
their projects include:
Distributed computer Vision With support from an NSF CAREER award,
Richard Radke, ECSE assistant professor, is developing
distributed algorithms for networks of cameras to gather and exchange
information for potential applications including terrain mapping, object
tracking, query-by-image-example, and view synthesis. Cameras dropped over a
battlefield, for example, have to figure out where they are in relation to
each other, a task Dr. Radke approaches by having them identify and exchange
information about unique features. Such a camera network must self-calibrate
without central command-and-control and be robust to dynamic, unreliable
communication channels and low-power contraints.
Robots that work well together
Wesley Huang,
assistant professor of computer science, is affiliated with Rensselaer’s
state- and industry-supported Center for Automation Technologies (CAT). His
research field is motion planning in distributed robotic systems. He is
interested in ways groups of autonomous mobile robots can coordinate among
themselves to accomplish tasks for such jobs as hazardous waste cleanup,
search and rescue, security patrolling, or reconnaissance.
Jeff Trinkle, professor and chair of computer science,
develops mathematical methods to model dynamic systems with discontinuities
such as robots that have unpredictable contact with their environment. He is
interested in systems such as dense nets of mobile sensors that could enter
a collapsed building, map it, and help determine the safest way to
disassemble the structure to rescue those trapped within.
Environmental Monitoring Rensselaer administers the Upper Hudson
Satellite Center of the new Rivers & Estuaries Center on the Hudson, a
research and education center supported by state and federal governments,
not-for-profit organizations, and other funding. A key portion of
Rensselaer’s mission is to develop monitoring, communication, and
visualization tools to analyze the Hudson, using both moored sensor systems
and autonomous underwater vehicles.
Sandra Nierzwicki-Bauer,
director of the DFWI, professor of biology, and a key collaborator on the
Hudson River Project.
Contacts: