Research Projects
This page summarizes our ongoing research projects; source code and
documentation (if made publicly available) can be found on our wiki (see
link above).
Real-Time Networks and Communication
- DARTS - Progressive Dynamic/Distributed Channel Reservations for Wireless Real-Time Streams: Many
wireless (ad-hoc and LAN) networks (e.g., sensor networks and embedded control systems) must support data dissemination with strict end-to-end latency
constraints. In addition, such networks are often resource constrained, e.g.,
they should support energy management techniques such as coordinated
sleep/wake mechanisms. Existing solutions to the real-time streaming problem
are inefficient in resource consumption and have large coordination
overheads (such as TDMA-based approaches) or they are unpredictable, i.e.,
they can only support soft real-time systems (such as contention-based
approaches). DARTS is a protocol that supports dynamic resource allocations
for real-time streams in wireless LANs and wireless multi-hop networks, where
each node dynamically negotiates (i) channel accesses for data transfers to
its neighbors (access points or next hops) and (ii) future negotiation
points, thereby ensuring contention-free communication and negotiation.
DARTS also performs end-to-end admission control along a stream's route to
ensure that all deadlines will be met under ideal network conditions.
- RTMC - Real-Time Multicast
Communication for Wireless Multi-Hop Networks:
Wireless multicast for multi-hop ad-hoc networks ensures
that the same information is delivered efficiently to
multiple recipients simultaneously. Many existing protocols
ignore the real-time nature of many wireless applications
such as real-time video and audio communications in mesh
and ad-hoc networks. Further, device in such networks
are typically energy-constrained, i.e., multicast protocols
have to trade off timeliness with energy efficiency. RTMC
is a real-time multicast protocol for wireless multi-hop
networks that allows receivers to specify their individual
real-time constraints and establishes multicast trees such
that receivers' deadlines are met and overall energy
consumption in the network is reduced.
- OTSP - Opportunistic Time
Synchronization Protocol for Mobile Ad-Hoc
Networks:
Time synchronization is crucial to the correctness of
many distributed real-time systems, including
wireless sensor networks. Numerous existing approaches
address both synchronization accuracy and efficiency
(e.g., communication and energy overheads). However, networks
of sensing devices are increasingly dynamic (e.g., changes
in topology), most notably due to the mobility of these
devices. Therefore, a synchronization approach is needed
that operates efficiently on mobile devices. Further, the
required clock accuracy of a sensor device depends o device
characteristics and application requirements, necessitating
configurable synchronization (which can be exploited to further
reduce the synchronization overheads). Therefore, the proposed
OTSP protocol provides a configurable and efficient time
synchronization scheme targeted at mobile sensor networks.
- Wireless Channel Access Reservations
for Resource-Efficient Real-Time Support:
Reservation-based channel access has been shown to be effective
in providing QoS guarantees in wireless and embedded real-time
applications such as mobile media streaming and networked
embedded control systems. While the QoS scheduling at the
central authority (base station) has received extensive
attention, the computation of actual resource requirements
at individual nodes has been widely ignored. Our research
studies strategies for nodes to determine minimal resource
reservations that guarantee the real-time constraints of their
network traffic. Further, this research studies integrated
resource management techniques that modify CPU scheduling and
DVS (Dynamic Voltage Scaling) techniques to ensure they
are aware of a node's limited communication opportunities
provided by such TDMA-style networks.
Ad-Hoc and Mesh Networks
- Courier - Publish/Subscribe Communication for MANETs:
The highly dynamic and unpredictable character of mobile
ad-hoc networks poses significant challenges for group
management. Node mobility often changes the multicast tree, and
therefore, frequent updates from group members are required to
refresh the tree at the source node. This results in high
communication overheads. Courier is a group communication
protocol that uses the location and velocity of roaming nodes
to provide bandwidth-efficient location updates from
subscribers, a mobility prediction model for predicting the
movements of mobile group members, and an overlay multicast
data distribution tree construction algorithm that is guided
by the mobility prediction model.
- NDMesh - An Experimental
Outdoor Wireless Mesh Network:
NDMesh is a wireless mesh netword deployed across the
campus of the University of Notre Dame. When completed, it
will consist of at least 30 roof-mounted solar-powered mesh
routers using 802.11b, 802.11a, and Zigbee radios. The mesh
network serves as educational and research tool for a variety
of networking, QoS, sensing, and control applications.
Further, each router is equipped with a video camera, providing
the foundation for research on video sensing and multimedia
applications. More information can be found on the
NDMesh wiki.
- CMR - Configurable Mesh/Ad-Hoc
Routers:
Wireless ad-hoc and mesh networks are increasingly used as
multi-purpose networks, i.e., they serve multiple objectives
and different applications simultaneously. As a consequence,
a one-size-fits-all routing solution is difficult to
achieve, particularly when the performance and QoS
epxectations of these applications differ. The CMR toolkig
supports the discovery and management of routes based on any
combination of a number of supported QoS metrics. This
enables network users to deploy customized routes that meet
their unique needs. Source code and documentation can be
found on the CMR wiki.
Sensor Networks and Mobile Applications
- PALER/DynaBIP - Reliable, Fast, and Resource-Efficient Retasking of Large Sensor Networks:
Re-tasking and remote programming of sensor networks is an essential
functionality to make these networks practical and effective. As the
availability of more capable sensor nodes increases and new functional
implementations continue to be proposed, these large collections of wireless
nodes will need the ability to update and upgrade the software packages they
are running. In order to do this, the new binary file must be distributed to
all nodes in the network. Making a physical connection with each individual
node is impractical in large wireless networks and standard flooding mechanisms
are too energy-costly and computationally expensive and they may interfere
with the network's current tasks. A reliable method for distributing new code
or binary files to every node in a wireless sensor network is needed. The
PALER/DynaBIP research
proposes a novel reprogramming/re-tasking framework for sensor networks that is
energy efficient, responsive, and reliable, while maintaining a stable network.
- TeamTrak - Cooperative Robust
Navigation:
The TeamTrak effort is concerned with localization of devices
in mobile ad-hoc networks without the support of any
infrastructure such as cell towers, beacons, etc. For example,
this research examines the utility of cooperatively sharing
location data among connected nodes in order to correct
positions with high measurement error in GPS-limited
environments. Using simple data sharing and filtering
techniques, collaborating users can substantially reduce
overall localization error in dead reckoning systems where nodes
may have a broad spectrum of location quality. More information
can be found on the
TeamTrak project site.
Funding
Our research is supported through grants
by the National Science Foundation, Army Research Office, Office of
Naval Research, Intel Corporation, Motorola Labs, and the University
of Notre Dame.