Research

Recent research projects:

RSSI-based sensor localization

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This research addresses mechanisms for mitigating the effect of shadowing that severely affects the error in location estimates using received signal strength indicators (RSSI). We explore practical mechanisms for utilizing redundancy of distance estimates obtained from a set of fixed beacon nodes to improve localization accuracy. Specifically, the following mechanisms are evaluated:

  • A correlation region based approach that applies a majority rule to determine the location estimate with maximum likelihood

  • An outlier based approach to minimize the effect of erroneous beacon signals

Delay minimization of intermittently connected networks

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This research involves ultra-low power energy harvesting sensor networks, where the rechargeable nodes often run out of power resulting in frequent and random link disconnections. We are developing models for intermittent link connectivity under various energy arrival and radio event characteristics, developing cooperative communication strategies to minimize link delay under energy constraints, and researching novel routing protocols that apply transmission diversity to minimize the end-to-end delay.

Rechargeable wireless sensor networks

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This research addresses strategies for achieving continuous and long-term operations of wireless sensor networks that are powered by energy harvested from renewable energy sources, such as solar. In such networks, the energy resources available at the sensor nodes varies significantly from node to node and also over time. The objective of this research is to design networking protocols that control the energy consumption at the nodes to adapt to such spatial and temporal variations of energy resources. Key components of this research include:

  • Development of energy availability models for rechargeable networks: this involves energy source prediction and energy storage modeling.

  • Development of adaptive networking protocols that allow variable energy consumption: this includes joint power control and routing protocols, multi-channel routing protocols, adaptive duty-cycling, and event-based sampling schemes.

Quality aware routing protocols for wireless mesh networks

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This research involved development of quality aware routing protocols and multichannel MAC for wireless mesh networks. Our research involves the following topics

  • Design of effective quality based route quality metrics

  • Joint channel selection and routing schemes

  • Anycast routing protocols

Experimental research on sustainability of large scale wireless sensor networks

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This collaborative research project with the Electric Power Research Institute (EPRI) involved the design and deploy WSNs for a number of monitoring applications in power generation stations and substations. Some of the components of this research project include:

  • Development of energy-efficient applications for monitoring the health of high voltage equipment in power substations and power plants

  • Load and energy aware routing

  • Beacon assisted self-localization schemes

  • Adaptive networking and signal processing schemes that enable the nodes to adapt to unpredictable spatial and temporal variations of energy resources that are caused by fluctuations of harvestable environmental energy at the node locations.

Other research projects:

  • Multi-channel medium access control (MAC) protocols for mobile ad hoc networks: We developed MAC protocols that employ dynamic channel selection mechanisms to improve the throughput in mobile ad hoc networks using the same aggregate resources, i.e. the same overall channel bandwidth and a single radio interface performing channel switching.

  • Multipath routing in mobile ad hoc networks: We developed on demand routing protocols for systematically determining and maintaining multiple alternate routes so that the frequency of route discoveries is dramatically reduced for re-establishment of routes during link breakages.

  • Protocols for directional antennas in mobile ad hoc networks: We developed MAC protocols that are based on practical adaptations of the IEEE 802.11 MAC to incorporate appropriate selection of the antenna directions for packet transmissions and receptions. The proposed MAC protocols provide higher throughput and lower average power consumption in the network. In addition, we developed an on-demand routing protocol using directional antennas that reduces the spread of routing packets by using directional transmissions.

  • Algorithms for resource constrained wireless sensor networks: We developed a number of novel energy-efficient algorithms for low-lower power wireless sensor networks. This includes:

    • GPS-free localization using an angle-of arrival estimation technique

    • Multi-sensor collaboration schemes using contour detection for spatio-temporal monitoring of slowly-varying signals

    • Serial data fusion scheme for the detection of weak signals

Funding (selected):

  • “Wireless Sensor Network for Valve Monitoring”, Burkert Contromatic Corporation, $131,448, A. Nasipuri (PI), J. Conrad, R. Cox, and B. Rodriguez-Medina. February 13, 2015 to December 31, 2016.

  • “Critical Infrastructure of the Distribution Grid”, Center for Advanced Power Engineering Research (CAPER), $48,450, B. Chowdhury (PI), A. Nasipuri, K. R. Subramanian, and C. Lim. Jan. 1, 2015 to Dec. 31, 2016.

  • “NeTS:GOALI: Towards Adaptability to Variations of Renewable Energy in Large Scale Rechargeable Wireless Sensor Networks”, National Science Foundation (NSF), $300,017, A. Nasipuri (PI), J. Conrad, R. Cox, L. Van der Zel, A. Phillips. September 1, 2011 to August 31, 2016.

  • “Scalability and Sustainability Issues of Wireless Mesh Sensor Network for Substation Monitoring”, supported by the Electric Power Research Institute (EPRI), $120,354, A. Nasipuri (PI), J. Conrad and R. Cox. September 15 to December 31, 2011.

  • “Wireless Mesh Sensor Network for Fossil Plants Monitoring”, supported by the Electric Power Research Institute (EPRI), $56,779, A. Nasipuri (PI), J. Conrad and R. Cox. February 25 to January 31, 2009.

  • “Wireless Mesh Sensor Network for Power Systems Monitoring”, supported by the Electric Power Research Institute (EPRI), $178,490, A. Nasipuri (PI), I. L .Howitt, and J. Conrad. September 1, 2006 to December 31, 2008.

  • “CISE Research Resources: Experimental Testbed for Mobile Network Protocols”, supported by the National Science Foundation (NSF), $100,000, T. Dahlberg (PI), A. Nasipuri, E. El-Kwae, and G. Ahn, (EIA-013079), Sept. 2001 to February 2005.

  • “Multi-channel CSMA Protocols”, NSF subcontract from University of Cincinnati, $54,784, A. Nasipuri (PI), from grant “Collaborative Proposal: Protocols for Mobile, Ad Hoc Networks”, (ANI-9973147), S. R. Das (PI) and A. Nasipuri, University of Texas at San Antonio, $157,772, Oct. 1999 to Sept. 2003.

  • “Power Efficient Protocols for Mobile Ad Hoc Networks”, NSF Research Experience for Undergraduates (REU) supplement, $14,250, A. Nasipuri (PI), July 2001 to Sept. 2002.

  • “Development of a Wireless Sensor Network Prototype for Supervision and Control of Bioreactor Landfills”, supported by the University of North Carolina at Charlotte, $6000, A. Nasipuri (PI) and V. Ogunro, 2004 – 2005.