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Title: A model-based approach to clock synchronization

Speaker: Nikos Freris

Abstract:

In a network of clocks, we consider a given reference node to determine the time evolution t. We introduce and analyze a stochastic model for clocks, in which the relative speedup of a clock, called the skew, is characterized by some given stochastic process. We study the problem of synchronizing clocks in a network, which amounts to estimating the instantaneous relative skews and relative offsets by exchange of timestamped packets across the links of the network. We present a scheme for obtaining measurements in a communication link. We develop an algorithm for optimal filtering of measurements across a link (i, j) in order to estimate the logarithm of the relative speedup of node j with respect to node i, and we further study some implementation issues. We also present a scheme for pairwise offset estimation based on skew estimates.We study the properties of our algorithms and provide theoretical guarantees on their performance. We also develop an online centralized model-based asynchronous algorithm for optimal filtering of the time-stamps in the entire network, and an efficient distributed suboptimal scheme.

Speaker Bio

Nikos Freris was born in Athens, Greece, in 1982 and lived in Chalandri. In 2000, he joined the department of Electrical and Computer Engineering (ECE) in the National Technical University of Athens (NTUA). As an undergraduate, he is exposed to various areas of ECE and Computer Science (CS) like Computer Engineering, System Theory and Controls, Signal Processing, and Software Engineering. At the last year in NTUA, he worked on the introduction and parameter estimation of a new mathematical model of pancreas, towards the feedback regulation of diabetes, in collaboration with Pr. George Papavassilopoulos (NTUA) and Pr. Vasilis Marmarelis (USC). In 2005, he entered the MS/PhD program at the University of Illinois, Urbana-Champaign where he works as a research assistant in the Decision & Control group at the Coordinated Science Laboratory. His advisor is Pr. P.R. Kumar, and they are currently working on fundamental limits on network time synchronization, and clock synchronization algorithms. His future research interests focus on system theoretic aspects of next generation Control Systems, with applications in Wireless & Sensor Networks and Networked Control. He was granted a Vodafone graduate fellowship for 2007-2008 for research in the area of Wireless Communication Networks. He is also a member of IEEE and the Technical Chamber of Greece.