Network Embedded Systems


ISIS has an active research program in the Network Embedded Systems area. Most of our projects deal with Wireless Sensor Networks (WSN). WSNs typically consist of many, low-cost and hence, resource-constrained devices. A typical node has a microcontroller, a few kilobytes of RAM and a low-bandwidth, range-limited radio. Battery power is limited and the communication is unreliable. These factors make building WSN applications extremely challenging.

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Over the years we have developed many fundamental services and interesting applications of WSNs. One of the fundamental services in any distributed system is time synchronization. Our Flooding Time Synchronization Protocol (FTSP) is one of the most widely used time sync services WSNs. Sensor node localization is another important area. As the nodes typically do not have GPS on-board, because of cost and power constraints, it is a challenging area. Our novel radio interferometric technique uses the radio itself without any additional hardware  to locate nodes with centimeter accuracy even at hundred-meter range. We have also demonstrated measuring the Doppler shift of the radio transmitter moving at slow speeds and used this information to track its location and speed accurately. Our paper on this technique received the Best Paper Award at SenSys 2007.

Our WSN-based countersniper system is able to locate shooters accurately at ranges of hundreds of meters as well as tell the projectile caliber and the rifle type at a high-degree of certainty. Our multi-channel acoustic sensor board detects the Time of Arrival (ToA) and the Angle of Arrival (AoA) of the shot. The fusion node receives the detection messages utilizing the implicit time synchronization service then locates and classifies the source. Our patented sensor fusion algorithm eliminates erroneous detections due to echoes prevalent in urban environments and resolves multiple simultaneous shots. The system and its predecessors have been demonstrated multiple times in different military bases.

Other WSN-based systems being developed at ISIS include a remote patient monitoring system, structural monitoring of railroad bridges, a mobile pollution monitoring network and others.

We have received support from Darpa, NSF, the US Army, the US Navy, Microsoft Research, Puritan Research and Crossbow Inc.