, Volume 13, Issue 2, pp 153-164
Date: 08 May 2006

Improved approximation algorithms for connected sensor cover

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Wireless sensor networks have recently posed many new system building challenges. One of the main problems is energy conservation since most of the sensors are devices with limited battery life and it is infeasible to replenish energy via replacing batteries. An effective approach for energy conservation is scheduling sleep intervals for some sensors, while the remaining sensors stay active providing continuous service. In this paper we consider the problem of selecting a set of active sensors of minimum cardinality so that sensing coverage and network connectivity are maintained. We show that the greedy algorithm that provides complete coverage has an approximation factor no better than Ω(log n), where n is the number of sensor nodes. Then we present algorithms that provide approximate coverage while the number of nodes selected is a constant factor far from the optimal solution. Finally, we show how to connect a set of sensors that already provides coverage.

A preliminary version of this paper appeared in The Proceedings of The Third International Conference on AD-HOC Networks & Wireless (ADHOC-NOW 2004)
Stefan Funke completed his Diploma and PhD degree at the Universität des Saarlandes in 1998 and 2001, respectively. Subsequently he spent time as a postdoctoral researcher at the Max-Planck-Institut für Informatik, the University of Illinois Urbana-Champaign, and one year as a visiting assistant professor at Stanford University. He is now researcher at the Max-Planck-Institut für Informatik. His main research interest lie in the areas of computational geometry, combinatorial optimization, and wireless networking.
Alex Kesselman completed his B.Sc. and M.Sc. degree at the Ben Gurion University in 1995 and 1998, respectively. Following that he was an R&D Staff Member at Motorola Semiconductor Israel and CheckPoint Software Technologies. He received his Ph.D. from the Tel Aviv University in 2003. Subsequently, Alex was a postdoc in Universita di Roma La Sapienza and Max-Planck Institut für Informatik. His research mainly focuses on algorithms for network optimization including algorithms for Internet switches, Quality of Service (QoS), network protocols and wireless ad hoc and sensor networks.
Fabian Kuhn received his M.Sc. degree in computer science (Dipl. Informatik-Ing ETH) from the Swiss Federal Institute of Technology (ETH), Zurich, Switzerland in 2001. In January 2002 he joined the Distributed Computing Group at ETH Zurich as a Ph.D. student and research assistant. In 2005 Fabian Kuhn earned his Ph.D. degree for his work on locality phenomena in distributed algorithms. He was awarded with the ETH medal for his Ph.D. thesis.
Zvi Lotker completed his Master and PhD degree at the Tel-Aviv University in 1998, 2003, respectively. Subsequently he spent time as a postdoctoral researcher at the INRIA Sophia Antipolis Mascot France, Max-Planck-Institut für Informatik Germany. He is now researcher at Centrum voor Wiskunde en Informatica in the Netherlands. His main research interest lie in the areas of networking, distributed computing and combinatorial optimization.
Michael Segal finished B.Sc., M.Sc. and Ph.D. degrees in computer science from Ben-Gurion University of the Negev in 1994, 1997, and 1999, respectively. During a period of 1999–2000 Dr. Michael Segal held a MITACS National Centre of Excellence Postdoctoral Fellow position in University of British Columbia, Canada. Dr.Segal joined the Department of Communication Systems Engineering, Ben-Gurion University, Israel in 2002 where he serves as departmentís Chairman. His primary research is algorithms (sequential and distributed), data structures with applications to optimization problems, mobile wireless networks, communications and security.