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.
