Check out the
Google Earth-based user interface
We have showcased several exciting technologies in an integrated demonstration.
The demo scenario is as follows: a plain cloth security guard walks around the stadium with
a cell phone-integrated radiation detector. The person also carries an XBow
XSM mote that we continuously track using an enhanced version of the
radio interferometric positioning technique introduced at the ACM SenSys conference in 2005. There
are 12 XSMs acting as infrastructure nodes deployed at known positions to
enable tracking with ~1m accuracy throughout the stadium. When the radiation
detector is in close proximity to a source, it sends an alarm using the mobile
phone network. This causes a remote controlled camera to automatically zoom
in on the position of the policeman. The large Jumbotron display in the
stadium shows the video as well as the
Google Earth-based user interface.
The tracking is done using a novel
radio interferometric technique developed previously under the DARPA NEST program. The tracked node
selects a neighbor and the pair acts as transmitters. They emit radio
waves in the 400MHz band that have ~350Hz separation. All other infrastructure
nodes measure the phase of the low frequency envelope signal that is the
result of the two signals interfering. The relative phase offset of pairs of
nodes provides information on the relative location of the four nodes involved.
It is possible to determine the position of one node if at least four other
nodes at known positions participate in the measurement. Additional nodes
are used to provide better coverage of the large area and to compensate for
errors introduced by RF multipath effects.
The security component (MultiMAC) provides group-based peer authentication
for sensor nodes. We use the SkipJack implementation in TinySec as symmetric
cipher. Each sensor stores a different set of keys in its ROM which is pre-defined by a key
mapping scheme. Multiple message authentication code (MAC)s of every message are
calculated in SkipJack, using the key set assigned to the sensor node.
The receiver authenticates the message by recomputing MACs using its common keys with the sender.
The radiation detector is a small, battery-powered gamma detector
connected to a mobile phone running a Java application reading the
detector output. The output is sent nearly continuously over the phone's
mobile data network to a server which checks the received gamma count
for a threshold crossing. If an elevated gamma reading is seen, the
server interfaces with the XSM system to determine the current location
of the policeman and sends a control message to the camera system.
The camera system consists of a controller unit communicating with one
or more cameras via a wireless network using the IEEE 1451 protocol. The
system can be used to point the camera(s) on demand, based on alert
conditions. The controller unit accepts position commands to slew, zoom,
and focus a camera on a specific location. The locations are specified
as coordinates (in any well-defined coordinate reference system) as well
as "field of view," which determines the zooming degree of interest.
Additionally, each camera's pan, tilt and zoom capabilities can be
directly accessed and controlled over the network.
This integrated demonstration showcases important technologies and
potential homeland security applications of sensor networks:
- highly accurate positioning and tracking using wireless sensor networks (ISIS-VU),
- sophisticated radiation detection capabilities (ORNL),
- secure sensor network architecture (ISIS-VU / TRUST),
- early example of the application of federated sensor networks
(ISIS-VU and ORNL),
- highly accurate fine grained camera control (ORNL),
- modular micro-operating system for sensor networks (UC Berkeley),
- low-power mote design (UC Berkeley, Crossbow, OSU)
- Tracking: Branislav Kusy, Gyorgy Balogh, Miklos Maroti (ISIS-VU)
- Wireless Sensor Network Technology: Andras Nadas, Peter Volgyesi, Janos Sallai (ISIS-VU)
- Authentication: Yuan Xue, Taojun Wu (ISIS-VU)
- Radiation Detection: Johnny Tolliver, David Resseguie (ORNL)
- Camera Control: Morey Parang, Mark Gardner (ORNL)
Pictures:
The picture below shows the 3D model of the stadium with the 12 infrasttucture motes along with the tracked mote in Google Earth:
The photo below shows the tracked person across the stadium:
The TV screen in the press room displays the live camera feed showing the tracked person:
