The Department of Computer Science at the University of Cyprus cordially invites you to the Colloquium entitled:

Query Optimization in Wireless Sensor Networks


Speaker: Dr. Georgios Chatzimilioudis
Affiliation: University of Cyprus, Cyprus
Category: Colloquium
Location: Room 148, Faculty of Pure and Applied Sciences (FST-01), 1 University Avenue, 2109 Nicosia, Cyprus (directions)
Date: Monday, Sept. 27th, 2010
Time: 14:00-15:00 EET
Host: Marios Dikaiakos (mdd AT and Demetris Zeinalipour (dzeina AT

The objective of this work is to optimize query execution in wireless sensor networks. To answer a query, data generated by the sensors need to be collected and processed. The cost of query execution is measured in the energy spent by the wireless sensor network. We minimize the energy needed by constructing sophisticated query trees that determine how data will be routed towards the sink and where the data will be processed inside the network. We propose query trees for optimizing two types of queries: queries that need data from all the nodes in the network and queries that need data from a subset of nodes only. For the former type of queries we minimize the energy consumption using communication balancing to minimizing the collisions during query execution. We propose a distributed algorithm to construct a near-optimal balanced communication tree with minimum overhead. Our algorithm outperforms previous work both in tree construction overhead and in tree balance. For the latter type of queries use operator trees and dynamic operator placement that minimize the bytes transmitted during query execution. We propose a centralized algorithm for constructing an operator tree and an initial operator placement based on an adaptation of the Fermat point problem (1-median problem) for a weighted graph. We also propose an optimal parameter-free decentralized algorithm to adapt the placement of a single operator.

Short Bio:
Georgios Chatzimilioudis received his Ph.D. in Computer Science in University of California Riverside in June 2010. His work focused on data management in wireless sensor networks and query otpimization in sepcific. He has also completed long-term internships at the R&D units of Siemens (2007) and Siemens Corporate Research (2008). Currently he is a post-doctoral fellow at the Computer Science department in University of Cyprus under the Marie Curie Transfer of Knowledge program. His primary research interests include data management and distributed query processing in wireless sensor networks, vehicular networks peer-to-peer systems.

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Sponsor: The CS Colloquium Series is supported by a generous donation from Microsoft